GE GEH-5201 User manual

•
GEH-5201 C Application and Instructions
Synchronous-Motor Control
,vith CR192 Microprocessor-based
Starting and Protection Module

GEH-5201, Synchronous-motorControl
Table of Contents
CONTENTS
Description Page Description
~~~~----------------------------~
Page
Section 1 - Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3
1.1 General 3
Section 2 - Starting Synchronous Motors. . . . . . . . . . . . . .. 3
2.1 General....................................... 3
Section 3 - Description of Synchronous-motor Controllers.. 6
3.1 General....................................... 6
3.2 Elements of a Complete Synchronous-motor
Controller. 6
3.2.1
CR192liSPM ................................. 6
3.2.2 Field Contactor . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 6
3.2.3 Field Discharge Resistor. . . . . . . . . . . . . . . . . . . . . .
.. 6
3.2.4 Solid State Field Exciter . . . . . . . . . . . . . . . . . . . . . .
.. 8
3.3 Synchronous-motor Field Panel
................... , 8
Section 4 - Description of the CR192 Micro-starting and
Protection Module. . . . . . . . . . . . . . . . . . . . . . .. 9
4.1 Description of Operation . . . . . . . . . . . . . . . . . . . . . . . .. 9
4.1.1 Starting and Synchronizing. . . . . . . . . . . . . . . . . . . .
.. 9
4.1.1.1 Reluctance Torque Synchronizing. . . . . . . . . . . . .
.. 9
4.1.2 Starting Protection . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 9
4.1.2.1 Reduced Voltage Starting
..................... 11
4.1.3 Power Factor (Pull-out) Protection ................ 12
4.1.3.1 Power Factor Operation
....................... 14
4.1.3.2 Controller Action During Pull-out
................ 15
4.1.3.3 Effect of Voltage Dips on Motor Power Factor
...... 15
4.1.3.4 Power Factor Detection and Indication when
Motor
Is Driven by Overhauling Load ............. 17
4.2 Specifications ................................. 18
4.2.1 Operating Temperatures ....................... 18
4.2.2 Power Source
................................ 18
4.2.3 Relay
Outputs ................................ 18
4.2.3.1 Relay Output Description ..................... 18
4.2.4 Current Transformer Input
...................... 19
4.2.5 Power Factor Analog Signal Output .............. 19
4.2.6 OptionallnputiOutputs ........................ 19
4.3 CPU Status Light ......................... 19
4.4 Non-volatile, Set-point Memory ......... " .... 20
4.5 Readout of Module Temperature . 20
4.6 Circuit Board Conformal Coating . . . . . . . . .. . ... 20
Section 5 - Optional Features
............... . · .. 21
.21
5.1 General .................. .
5.2 Exciter Voltage Check Display
..
5.3 Exciter Voltage Display ...... .
5.4 Field Current Loss Protection ..
5.5 Field Current Display ....... .
5.6 Incomplete Sequence Protection ...... .
5.7 Power Factor Regulation ..... .
5.7.1 Regulator Tune-up Instructions. . ..... .
· .. 21
.... 21
. . 21
· .... 21
· .... 21
· .. 21
· .... 21
Section 6 - Installation and Start-up ................... 23
6.1 Receiving and Installation ........................ 23
6.1.1 Installing Complete Controller Equipment
.......... 23
6.1.2 Installing Field Panels
.......................... 23
6.1.3 Component CR192 liSPM ....................... 23
6.2 Start-up Procedure
.............................. 24
6.2.1 Inspection ................................... 24
6.2.2 Grounding ................................... 24
6.2.3
Test Checks .................................. 24
6.3 Start-up Description
............................. 25
6.4
liSPM Displays ................................. 25
6.5 liSPM Messages ................................ 25
6.6 Interchangeability with earlier CR192 Modules ........ 27
Section 7 - Ordering the CR192 liSPM ................. 28
7.1 General. ...................................... 28
Section 8 - CR192 liSPM Programming Instructions ...... 29
8.1 Programming Procedure ......................... 29
8.2 liSPM Programmable Parameters
.................. 29
8.3 Explanation of Standard Set-points
................. 30
8.4 Explanation of Option Set-points ................... 31
8.5 The liSPM Keypad .............................. 31
8.6 Programming Example .......................... 33
Section 9 - Brushless Motor Control ................... 35
9.1 Description of Brushless Controller ................. 35
9.1.1 Brushless Motor Review ........................ 35
9.2 Starting the Brushless Motor ...................... 35
9.3 Protecting the Brushless Motor .................... 35
9.3.1 Stall Protection ............................... 35
9.3.2 Power Factor (Pull-out) Protection ................ 37
9.4 Options for Brushless Controls .................... 38
9.5 Ordering the Brushless liSPM ..................... 38
9.6 Programming the Brushless liSPM ................. 38
9.6.1 Procedure ................................... 38
9.6.2 Programming Example ......................... 38
Section 10 -Trouble Shooting ........................ 39
Section 11 -Renewal Parts .......................... 41
11.1 List of Renewal Parts ........................... 41
Section 12 -Terminal Point Layout .................... 42
Section 13 -Outline Dimensions ...................... 43
Section 14 -Calibration Module -Elementary Diagrams .. 45
14.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
These instructions do not purport to cover all details or variations in equipment nor to provide for every possible contingency to be met in connection with installation,
operation or maintenance. Should further information be desired or should particular problems arise which are not covered sufficiently for the Purchaser's purposes, the
matter should be referred to the nearest General Electric Sales Office
2

SECTION 1 - Introduction
1.1 General
These application notes and instructions apply to General
Electric Synchronous-motor Controllers and field panels that
employ a CR192 Microprocessor-based, Synchronous-motor,
Starting and Protection Module (IlSPM). These instructions also
apply to the CR1921lSPM when it is supplied as a separate
component. If the complete controller is not supplied, the
purchaser is requested to interpretthese instructions for
applicability to his particular assembly by referring to the
diagrams shown in Figures
10 and 23 to develop his diagrams
for his particular equipment.
Brushless synchronous motors can also be controlled by
the proper CR192IlSPM. See Section 9 for discussion of the
Brushless Synchronous-motor Control.
SECTION 2 - Starting Synchronous Motors
2.1 General
The most attractive and widely applied method of starting
a synchronous motor
is to utilize squirrel cage windings in the
pole faces of the synchronous motor rotor. The presence of
these windings allows for a reaction (or acceleration) torque to
be developed in the rotor as the ac excited stator windings
induce current into the squirrel cage windings. Thus, the syn-
chronous motor starts as an induction motor. These rotor
windings are frequently referred to
as damper or amortisseur
windings. The other major function
of these windings is to
dampen power angle oscillations after the motor has synchro-
nized. Unlike induction motors, no continuous squirrel cage
torque
is developed at normal running speeds. See Figure 1.
When the motor accelerates to near synchronizing speed
(approximately 95 percent synchronous speed), dc
Stator
Slip
rings
Rotor
Figure 1. Salient-pole synchronous motor
Stator
core
Slots
for ac
winding
To dc
current is introduced into the field windings in the rotor. This
dc current creates constant-polarity poles in the rotor which
cause the
motor to operate at synchronous speed as the
rotor poles
"lock" onto the rotating ac stator poles.
Torque at synchronous speed is derived from the
magnetic field produced by the dc field coils on the rotor
linking the rotating field produced by the ac currents in the
armature windings on the stator.
Magnetic polarization
of the rotor iron is due to phYSical
shape and arrangement of the rotor plus constant potential
direct current in coils looped around the circumference
of
the rotor.
Synchronous motors possess
two general categories of
torque characteristics. One characteristic is determined by
the squirrel-cage design, which produces a torque in relation
to "slip" (some speed other than synchronous speed), and
only in relation to slip since it can develop no torque unless
there is slip. The other characteristic is determined by the
flux in the salient field poles on the rotor as it runs at syn-
chronous speed. The first characteristic is starting torque,
while the second characteristic is usually referred
to as syn-
chronous torque.
In the starting mode, the synchronous-motor salient poles
are not excited by their external dc source. If the poles were
excited there would be no useful torque developed by them. The
reason for this is that the average torque due to field excitation
during
Slip would be a negative or braking torque that would
result in reducing the total amount of acceleration torque. In
addition, there is a very large oscillating component of torque at
slip frequency produced by field excitation which could result in
damage to the motor if the full field current was applied during
the whole starting sequence. Therefore, application of direct
current (dc) to the field is usually delayed until the motor reaches
a speed from which it can be pulled into synchronism without
slip.
At synchronous speed, the ferro-magnetic rotor
poles become magnetized, resulting in a small torque
(reluctance torque) which enables the
motor to run at
3

GEH-5201, Synchronous-motorControl
SECTION 2 - Starting Synchronous Motors
very-light loads in synchronism without external excitation.
Reluctance torque can also pull the motor into step if it is
lightly loaded and coupled to low inertia.
It is convenient to make an analogy of a synchronous motor
to a current transformer for the purpose of demonstrating
angular relationship of field current and flux with rotor position.
If 11 * is an equivalent current in the stator causing the
transformer action, then 11 will be about 180. degrees fn;>m 12 (or
I
FD
), and the flux will be 90. degrees behind I
FD
.Very significantly,
then, the
pOint of maximum-induced flux (0) occurs as the
induced field current
IFD passes through zero going from
negative to positive; maximum rate ofchange of current. See
Figure 2.
The rotor angle at which 11 and 12 go through zero will
depend upon the ratio of reactance to resistance in the field
circuit. A very high value of reactance to resistance will shift the
angle toward minus 90. degrees (-90.°). Reactance is high at low
speed (high frequency). At high speed (lOW slip, low frequency),
reactance decreases and the angle will shift toward
0. ifthe
circuit includes a high value of resistance. As the stator goes
beyond minus 45 degrees (-45°), the torque increases (essen-
Electrical
Degrees
Rotor Angle 135 45
90. 0.
(-45)
225 135
180.
Figure 2. Transformer action of rotor flux and current
(constantslip) for a typicalmotor
tially due to increased statorflux). At this point IFD yields a very
convenient indicator of maximum flux and increasing torque
from which excitation is applied for maximum effectiveness.
If the field discharge loop is opened at the point of maximum
flux, this flux is "trapped." Applying external amperes to the
current path in correct polarity to increase this trapped flux at
this instant makes maximum use of its existence. At this point
*11 is not an actual current. The transformer action is due to
stator flux (not shown) cutting the rotor winding.
4
Electrical
Degrees
Rotor
Angle
Trapped Flux
135 45
90.
(-45) Pull-in
315 .-"'-..
0. 270. 0.
360.
Applied IFD
Field
Discharge
Loop Opened
IFD
(Induced)
Figure 3. Rotorflux and current at pull-in (typicaldesign)
the stator pole has just moved by and is in position to pull the
rotor forward into synchronous alignment. See Figure 3.
Approximate Sta-
tor Position For
-1 Rotation Maximum Field
i- -45?.. R Pole Flux (Depend-
N \ ~ ing Upon Design &
~+-+---'r_s -y -90.
0 RDIS)
RDIS
N4- Approximate Sta-
tor Position For
Maximum Torque
When
Maximum
Rotor Flux Occurs
At -45
0
Note: Angular displacement of rotor with
respect to stator is given a negative
sign
to indicate the motoring con-
dition.
Figure 4. Angulardisplacement of rotor
It has been established that salient-pole torque near
synchronous speed is a function of both slip and field-discharge
resistance. Figure 6shows the combined effects ofcage torque
and salient pole torque for a typical motor. Figure 5 shows the
effect of a highervalue of discharge resistance on a medium-
torque motor. Obviously, without salient-pole torque the motor
would cease to accelerate certain loads at some point on the
speed axis.

SECTION 2 - Starting Synchronous Motors
Total
200
~ 150
!!
0
f-
.-
c 100
<J.)
~
<J.)
a..
50
0 0
25
50
75
1
100
Percent Speed
95
Figure 5. High-starting-torque motor
~ 150
!!
0
f-
.-
c
100
<J.)
~
<J.)
a..
50
0 0
Total
Salient Pole /
Contribution ~ I
--
50 1100
95
Percent Speed
Figure 6. Medium-starting-torque motor
A high value of FDRS is not used every time, because of the
other function of the resistor, which is reducing field voltage to
safe levels during starting. As the FDRS value increases so does
the induced voltage, and
at some point this voltage would be
damaging to insulation orother components
in the field circuit.
Solid-state excitation and control components in the field circuit
have had the effect of making the value of FDRS and its voltage
effect more significant. There is a greater sensitivity to field
voltage tolerance levels with solid-state components.
<J.)
::J
High
Discharge
Resistance
150~---------+--~~--~---
!! 100~--~~~-4--~~--~-H--
~
'E
<J.)
u 50~----------4-----------~f--
Q;
a..
50 95100
Percent Speed
Figure 7. Medium-starting-torque motorwith two values of
field discharge resistance
Selection ofthe value of the field discharge resistance is a
decision that may require judicious application of several factors
present on a particular drive, such
as torque, excitation systems,
and control components.
The importance ofspeed for applying field cannot be over-
emphasized. Rotor and load masses cannot be accelerated fast
enough to allow synchronization, if slip is in excess of ten
percent.
Synchronous-motor controllers which can accuratelyapply
field at an optimum speed and a favorable angle permit match-
ing the motorto the load with a greater degree of precision than
might otherwise be possible. The increase in load which can be
pulled in dueto precision application of field will vary from one
motor design to another along with system inertia.
Applying excitation at the point of zero induced current
(favorable angle) takes advantage of motor capability in two
ways.
(1) It catches ("traps") salient-pole flux at significant
magnitude(provided there is a field discharge resistor of
adequate value) and uses it for torque during a 180 degree
(180°) acceleration period. (2) It catches the rotor in correct
angularposition to be pulled forward into step.
In addition to permitting closer matching of motor to load,
optimum application of excitation also reduces powersystem
disturbance which occurswhen the motor goes through a
complete slip cycle with the field energized. If the motor is large
relative tothe power system, surges transmitted to the system
will be at a minimum if field is applied to prevent slip at pull-in.
5

GEH-5201, Synchronous-motorControl
SECTION 3 - Description of Synchronous-motor Controllers
3.1 General
Synchronous-motor Control equipment can be supplied
either as a complete controller (including an ac power switching
device for the motor starter) or as a field panel (ac power
switching supplied by others).
3.2 Elements of a complete
synchronous-motor controller
The complete Synchronous-motor Controller has the ability
to switch the motor on to and off of the power system and protect
the motor from damage that can occur if the motor is running
in
an abnormal condition, such as out-of-synchronism.
Figure 8. Front view of CR192 JJ.SPM
The complete Synchronous-motor Controller consists of the
Motor-starter, Switching device (typically a contactor) which
controls the main powerto the motor.
In addition, protective
relaying is provided (such as overload relays) and control for
starting and stopping the motor (start-stop pushbuttons).
Indicating devices such as line ammeters are supplied. All of
these features are common with motorcontrollers of all types.
6
RIBBON
RELAYS
FUSE
Figure 9. Backbase view of CR192 JJ.SPM
In addition to full voltage starting, synchronous motors may
be started by either reduced inrush methods, such as primary
reactor, auto-transformer or part-winding control.
The following elements are unique to synchronous
controllers.
3.2.1 The CR192 micro-starting and
protection module
This electronic, microprocessor-based module provides the
computation and monitoring functions necessary to synchronize
and protect the synchronous motor from stall, prolonged
acceleration, or pull-out conditions. This device is discussed in
more detail starting
in Section 4.
3.2.2 Field contactor
This low-voltage contactor applies and removes dc power
to the synchronous motor field and switches the field dis-
charge resistor. This device may be either solid state or elec-
tro-mechanical.
3.2.3 Field discharge resistor
This resistor bank (sometimes shipped as a separate item)
is used to discharge the magnetic energy of the field during
shutdown and absorb induced field energy during start-up.

SECTION 3 - Description of Synchronous-motor Controllers
Ac Source
,- ______ AL ______ _
L2
b)
TYPical Elementary Diagram Ring-type
SynChronous Motor Controller, Full- ~oltage
Nonreverslng (With OptIOnal Digital Field Current
Display and Voltage Check Protection)
,l-L5PM
(135) (13T)
FC
FI
Synchronous
Molar
Field
F2 FC
L- ____ --,
: FDRS
(V+)
~----<O-----~
(R3)
r---------------,
I '
I
Required
ExternaI
Resistor
" (+) ( _ ) Assembly
~~~------~--~~v~--~~--------~~/
DC From Exciter
Fu
T GND
L
,l-LSPM 2PB ~
(TRPI) BTRP2) .,.......-----.---<
CM M
r------
01 20
MX
FC
~ fL
SPM
3 230 VA C 4 , ~ f----<>-_-(
L-=~=="=5=V=A=C==__-J-~M ~ (FARI) (FA R21
MX M
,I-L 5PM
(V I) r-:D"""'i:-g-II-a'-I '-L-I n-e-----:-A-m-p-s-, - (V2)
Field Amps And PF
Display
(NX I)(NX2) (-IE)(+IE) (MX)(MXI)
On reduced voltage starters,
remove jumper and connect a (6) (5)
N.O. auxiliary contact from Ihe
final slep conlaclor here.
,l-LSPM
1----0---,
(FCX I) (FCX2)
V
To Aula Loader
Fu
Nomenclature
CB
- Ci rcu it Breaker
CM
- Field Currenl
CalibrallOn Module
1,2,3, CT -Currenl
Tra nsformer
DCCT -Direct Current CT
FC - Field Conloclor
FDR5 - Field Discharge
Reslslar
Fu -Fuse
GND -Ground
LI, L2, L3 - Incoming
M
MX
fL
SPM
OL
Terminals
- Main Contaclar
- Auxiliary To M
-
CRI92 Mlcro-
slarllng And
Protecllon Module
- Overload Relay
IPB - SIart Pushbutton
2PB - Slop Pushbutton
PM - Polarity Mark
Supp - Noise Suppressor
TI, T2, T3 - Motor Terminals
T - Transformer
... -The excller vollaqe
must be presenl before
starling Ihe motor If
voltage check proteclion
is provided
Figure 10. Typical ring-type, synchronous motorcontrollerelementary diagram
7

GEH-5201, Synchronous-motorControl
SECTION 3 - Description of Synchronous-motor Controllers
3.2.4 Solid-state field exciter
General Electric Synchronous-motorControllers may be
supplied with either; (1) diode-rectifier/tapped transformer field
exciter or (2) Silicon Controlled Rectifier exciter. Ofcourse,
provisions can be made for remotely supplied dc field power.
These two exciter types are described as follows:
1. The diode-rectifier/tapped-transformer exciter utilizes a
full wave bridge rectifier(either single or three phase) to obtain
the required
dc field supply. Atapped transformer provides a
wide range of available secondary voltages so that the desired
field current may be obtained by properchoice of the
transformertap. The motor must be shut down before the
transformertap can be changed.
2. The Silicon Controlled Rectifier (SCR) Exciter is
available when anyone ofthe following features is required.
8
A. ON LINE FIELD ADJUSTMENT. A lockable control
knob is provided either on the door or base mounted
inside the enclosure. Adjustment of the knob
increases ordecreases the field current
conveniently while motor is running.
B. FIELD CURRENT REGULATOR. As a synchronous-
motor field heats up while running, its resistance
increases causing the field current to drop. This
condition causes the power factor to
vary, resulting
in undesirable voltage fluctuations or nuisance
tripping from synchronous motor pull-out. A field
current regulator senses the field current and
causes the SCR to either increase or decrease its
output in orderto maintain a constant field current
regardless of field winding temperature.
C. POWER FACTOR REGULATOR. Power factor
regulation is useful in those applications where
motors are subjected to high-level transient impact
loads (such as chipper drives). The PF regulator
senses the power factor dip that occurs when the
motor is loaded and causes the SCR Exciterto
respond with a boosted output.
As a result, the pull-
out torque ofthe synchronous motor is increased
for the duration of the transient load. After the load
subsides, the regulator senses an excessive
leading powerfactor and causes the SCR to reduce
its output. This automatic boosting of field current to
avoid pull-out is called field forcing. The Power
Factor regulator thus provides automatic boosting
when field forcing is required and economical low
field operation when the motor is idling.
Another application of the power factor regulator is
to control power factor swings that result from
various levels of loading
so as not to cause
fluctuations in the, plant system voltage.
The JlSPM provides the.control signal to the SCR
exciterwhen PF regulation is required. See
Section 5.7.
3.3 Synchronous-motor field
panel
The Synchronous-motor Field Panel contains at least the
features listed in the previous section that are unique to the
Synchronous-motor Controller. Additionally, the Synchronous-
motor Field Panel may include stator protective relaying and
start-stop control
as well. However, the field panel will not switch
or handle any of the line power to the synchronous motor stator
windings.
Hence, the field panel becomes a piece of control equip-
mentthat can interconnect with eithera separate contactor or
circuit breaker to form a complete Synchronous-motor Controller
orfeeder.
Field panels may be supplied with solid-state field exciters.
See Section 3.2.4.

SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
4.1 Description of operation
4.1.1 Starting and synchronizing
Control functions for starting the synchronous motor
include the following.
1. Applying power to the stator; at full voltage or at
reduced voltage.
2. Shunting the field with a discharge resistor. (FDRS)
3. Sensing rotor speed.
4. Sensing rotor angle.
5. Applying excitation at optimum speed and angle.
6. Reluctance torque synchronizing.
The first step in starting a synchronous motor
is to apply
power to the stator by means of a magnetic contactor or circuit
breaker.
Shunting a resistor around the motor field during starting is
accomplished by a field contactor. Optimum application of
excitation (that is, closing the field contactor) requires accurate
sensing of motor speed and rotor angle. This function is pro-
vided by the CR192 {(SPM. Optimum speed for pull-in will vary
somewhat from one motor design to the next, and with the value
of the field discharge resistor. Adjustment of the control to apply
field at various values of motor speed is important. Correct rotor
angle for field application does not vary, and is always the point
where induced field current passes through zero going from
negative to positive; the point of maximum flux in the rotor. See
Figure 3. Maximum utilization of motor pull-in capability will
depend upon the degree to which the control can accurately
sense speed and rotor angle.
Rotor frequency is the most positive electrical parameter
available for indicating speed, and can
be sensed by detecting
frequency of the voltage across FDRS. Voltage across FDRS is
not actually
"induced field voltage," but is the voltage which is
essentially
in time phase relation to the current through the
resistor. That is, the current goes through zero at the same time
the voltage goes through zero.
Figure
11 is included to illustrate the electronic circuits of
the CR 192 pSPM which detect the proper rotor speed (PRS) and
rotor angle (PRA) signal.
Outputs from the PRS and the circuits are fed into a Central
Processor Unit
(CPU) to determine the proper time to close the
Field Application Relay
(FAR). When th~ proper rotor speed and
the proper
rotor angle conditions are met as determined by the
microprocessor
(CPU), the CPU delivers a signal to the FAR
Relay so it can close its contact FAR1-FAR2. FAR picks up field
contactor
FC to apply excitation to the motor field and to open
the field discharge resistor
loop. See Figure 10.
Speed at which the motor is to synchronize (PRS) can be
programmed over the range of 90 to 99.5 percent speed. (See
Programming Instruction, Section 8.)
4.1.1.1 Reluctance torque synchronizing
A synchronous motor that is lightly loaded and connected to
low inertia load may pull in to synchronism before the rotor poles
are externally magnetized. This is commonly known as reluc-
tance torque synchronizing. This magnetization can result in
sufficient torque to hold the salient poles in direct alignment with
corresponding stator poles and run the motor at synchronous
speed. When load is applied, however, the rotor will begin to slip
since the torque developed is only a fraction of rated torque
under separate excitation. Furthermore, the rotor is polarized by
the stator flux under this condition and can therefore be polar-
ized in any direct axis alignment; occuring each 180 degrees.
External excitation forces pole-to-pole alignment in only one
orientation of the direct axis.
Should the rotor pull in to synchronism 180 degrees away
from the normal running alignment, external excitation will build
up flux in the rotor in opposition to the stator flux. As the external
excitation builds up, correct alignment of rotor to stator will occur
by slipping one pole and the motor will then run in normal
synchronism.
The Field Application Control must respond in such a way
as to proceed with proper application of excitation in the event
the motor does synchronize on reluctance torque. Figures
12
and 13 show how the pSPM automatically responds to reluc-
tance torque synchronizing.
4.1.2 Starting protection
The amortisseur, or cage winding of a synchronous
motor, is probably the element most susceptible to thermal
damage. Its
function is essentially operative only during star-
ting, and there are limitations on space available for its con-
struction onto the rotor. Hence, it is usually made of lighter
material than the cage winding of an induction motor. The
cage is
also vulnerable to overheating should the motor be
allowed to run out of synchronism with no excitation. In this
case, it runs as an induction motor at some value of slip
which will produce cage current that develops running tor-
que. However, the cage of a synchronous motor is not
designed for
continuous operation. Therefore, an important
protective function of the controller is to prevent overheating
of the cage winding both during starting and running out of
synchronism.
Monitoring the starting condition
of a synchronous motor
can
be accomplished by looking at the frequency of induced
field current, the same procedure used to accomplish synchro-
nizing. Metor designers always place a limit on the time a
particular motor can be allowed
to remain stalled ("allowable
stall time"*).
An accelerated schedule can then be established.
• "Allowable stall time" is important for the induction motor also,
but the time is usually shorter for the synchronous motor and
varies from one design to another in terms of greater spread.
9

GEH-5201, Synchronous-motorControl
SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
10
Motor
FC F1 Field F2 FC
------III--~------r~y~y~y~'--------4 ... --Ill--l -----
J
~ FC
I FDRS
5V
MOV
-----
I \ -
1
.- HCPL
T 3700
U1 ~
CR11-- ___ ....J V
\
PRS
COM
5V
----.. MOV
\ -
\
VOLTS I--' VOIS HCPL
3700
U2 I
~
')-'
PRA
+40V - - -- --
-------+-
~\J
I
rt---- - PRS PULSES COM
-40V
-----1--------
In
n PRA PULSES
Only the zero-
crossing
of VOISAC
waveform is shown.
Figure
11
Positive half cycles of VOIS are clamped by CR1, thus allowing U1 to stop conducting. PRS
signal then goes to 5V. Negative half cycles (more negative than -40V) causes U1 to conduct
pulling PRS to ground. Results are a square wave representative of VOIS offset by -40V.
± VOIS causes U2 to conduct anytime it is greater than ± 40 volts causing PRA to be pulled to
ground. When VOIS is less than 40V, U2 stops conducting and allows PRA to go to 5V. Results
are a 5V pulse indicating when VOIS is crossing zero. The CPU senses PRS and PRA, deter-
mines when proper synchronization speed is reached, and closes the field
contactor at the pro-
per electrical angle.
Figure 11. Determining proper synchronization speed

SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
Excitation
Applied
~r
PRA
IF
Operation
For correct orientation
of the reluctance-torque rotor
magnetization_
PRS times out first and the PRS flag
is set.
PRA flag is set when VDIS falls below ± 40V_
Since both PRA and PRS flags are set simultaneously,
the field is applied.
Figure 12. Correctorientation of the reluctance-torque-rotor
magnetization
Excitation
Applied
t-
PRS
PRA One-pole Slip
Operation
For
180 degree dis-orientation of the reluctance-torque
rotor magnetization,
PRA flag is set when VDIS falls
within the range of ± 40V. At this point, PRS starts
timing. When
PRS times out, the PRS flag is set. PRA
and PRS flags now appear simultaneously and the field
is applied.
Figure 13. Motorsynchronizes on reluctance torque-rotor
disoriented
180 degrees
for the motor in terms of running time at any speed less than
synchronous
as a percent of allowable stall time. Increased air
circulation from the rotor fan reduces heating rate
as the motor
accelerates. Frequency can be measured directly as
an indica-
tion of speed, and the designer's curves for speed versus time
can
be used for protection by software that integrates the
time-speed function_ Figure
14 shows the typical cage
heating protection characteristics during acceleration_
The time-speed function shown in Figure
14 is accom-
plished internally by the
I-tSPM software_ The I-tSPM determines
the motor speed from the induced field voltage frequency. The
programmed values for maximum allowable stall time and 50
percent speed run time determines which particular characteris-
tic of protection is needed from the family of curves shown in
Figure
14_
4.1.2.1 Reduced-voltage starting
Many synchronous motor starting applications involve
either reduced voltage (starting reactor or auto-transformer) or
part-winding starting methods. When these methods are used,
the available torque for acceleration is reduced from the torque
that would result from a full-voltage start. Also, the allowable
stall time of a motor is extended during a reduced-voltage start
due to the reduced heating-rate resulting from lower inrush
currents_
The CR192
I-tSPM has the ability to take advantage of
the motor's extended stall time so that the motor and load
can accelerate to synchronous speed in a time period longer
than would
be allowed with a full voltage start. The accelera-
tion torque is reduced as the square
of the ratio of reduced
voltage to full voltage, and the motor-heating rate is propor-
tional to the square
of the starting current Since the motor
inrush current is reduced proportionally with the voltage
reduction (due to the constant impedance
of the syn-
chronous motor at stall) the following allowable stall time
factor applies:
(lpLR/IMLR)2
IpLR = Programmed full voltage locked rotor current.
IMLR = Measured inrush current.
This ratio can be used
as a factor for increasing the stall
time above the full voltage allowable stall time for any given
speed. See Figure
15.
The I-tSPM calculates the ratio, squares it, and factors this
value into the stall time algorithm approximately one-tenth of a
second after motor starts. When the final step contactor closes
and applies full voltage to the motor windings, a N.O. interlock
from this contactor is wired to the
I-tSPM to signal that the motor
is now
at full Voltage. The correction factor for reduced voltage
startsthen immediately becomes unity.
If, for any reason, it is not desirable to have this ratio
correction factored in, ajumper may be placed across inputs
NX1 and NX2. Conversely, if the motor is started from a weak
system, and significant voltage dips are expected during
starting, the factory jumper from
NX1 to NX2 may be removed_
The I-tSPM will automatically extend the stall and accelerating
time per the reduced voltage factor.
11

GEH-5201, Synchronous-motorControl
SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
200
150
100
80
60
50
40
30
25
20
15
1
71
II/ 1
)
~/I
10
8 7
117~
I I
Ratio of
6
Allowable 5
Running 4
Time
to
Allowable 3
Stall Time
at Zero 2
Speed
1.5
1
~ I I I
7 I II I
/
VI
I
/ / /
1/
'"
'/
V / J
/ V
.........
i,/
V
/v
~
t::::::
V
..,....
V
~
-
...--
o
10 20 30 40 50 60 70 80 90 100
Percent Synchronous Speed
Figure 14
NOTE:
To find the protective characteristic used, plot the programmed value for 50 percent run time
and draw in the complete curve through the plotted point using the above curves as a guide.
Figure 14. Amortisseurwinding (squirrel cage)protective for stall and acceleration at full voltage
4.1.3 Power factor (pull-out) protection
poles on their rotors magnetically linking opposite stator poles.
Whenever the rotor turns at a speed less than that of stator
rotating field, the motor is said to
be slipping poles. Slip can
occurwith the field poles magnetized while running in synchro-
nism from the following four major causes.
Synchronous motors are designed to run at constant speed
and drive shaft loads from torque derived from the magnetic
12

SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
CD Full line voltage stall/acceleration
characteristic (from Fig. 14)
@ Adjusted characteristic for 90 percent
line voltage
@ Adjusted characteristic for 80 percent
line voltage
@) Adjusted characteristic for 65 percent
line voltge
@ Adjusted characteristic for 50 percent
line voltage
Ratio of
Allowable
Running
Time to
Allowable
Stall Time
at Zero
Speed
200
150
100
80
60
50
40
30
25
20
15
10
8
6
5
4
3
2
1.5
v
j
I
7
/ J
VI
I I
/ /
/ I J
,I
V
:/J W
/ /
/,
rJ
®
./
/
,1/
v
//
-,v
/' /
VI
V
I--'"
/'
Vh
v
---
0-
.-
[.../
V V
v
.....
@
~
~
I---
~
V
~
~
V
I--
--'
~
t:::=-
L-cD
o 10 20 30 40 50 60 70 80 90 100
Percent Synchronous Speed
NOTE:
These curves show how the trip characteristic of the amortisseur winding protection is adjusted
for reduced voltage starts. For
this example, curve 1 is taken from one of the family of curves in
Fig. 14.
Figure 15. Adjustment of stall/acceleration times forreduced voltage starts
1. A gradual increase in load beyond the pull-out
capabilities of the motor.
2. A slow decrease in field current.
3. A sudden large impact load.
4. A system fault orvoltage dip lasting long enough to
cause pull-out.
Loss of synchronism with field applied will create intense
pulsations in torque at the motorshaft each time a stator pole
13

GEH-5201, Synchronous-motorControl
SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
passes a rotor pole. Corresponding pulsations occur in line
current. Both types of pulsations can be damaging. Torque
pulsations can break a shaft, coupling, or other mechanical
elements, and current pulsations can interfere with smooth
power system operation. Slipping poles with field applied is
always unacceptable for a synchronous motor, therefore some
means must be provided to prevent this condition from occur-
ring.
One of the most reliable indicators of synchronous and
asynchronous (out-of-step) operation is the motor power factor.
Power factor is related to the phase angle between voltage and
current. Synchronous motors seldom, if ever, operate continu-
ously at lagging power factor. Synchronous motors run at either
unity or some value of leading power factor. Lagging power
factor appears when the motor load angle increases beyond
rated, becoming almost fully lagging (90 degrees) as the motor
slips out-of-step. Therefore, lagging power factor can be utilized
to initiate action to prevent slipping.
Torque and power pulsations during slip can be reduced by
removing field current to the rotor poles. The motor will then run
L1 L2
L3
PT or
essentially as an induction motor on its amortisseurwinding.
Slip with the field current removed is tolerable to the load and
power system but intolerable for any length of time to the motor
amortisseur winding itself, since the winding is designed with
limited thermal capability and for short-time operation. Motor
Power Factor during induction motor operation (that is with field
removed) is always lagging. However, the degree to which the
current lags the voltage
is less than at pull-out when field poles
are excited. Lagging power factor can again be utilized as an
indicator of "slip" during induction motor operation.
For synchronous motors, power-factor monitoring can be
employed to guard against pull-out or loss of field conditions.
4.1 .3.1 Power factor operation
Motor pull-out protection is provided by a circuit which
monitors power factor and has a built-in time delay to prevent
inadvertent tripping on transients. The
J,!SPM senses power
factor by monitoring thevoltage across motor Phases One and
Two and the current in Phase Three. See Figure 16. Figure 17 is
PM CPT V1
14
~
F1 Field F2
V,2 GJ
COM
C -Wave Clipper
PM -Polarity Mark
NOTE:
Square waves are generated internal to the IlSPM that are in sync with zero-crossings of 13 and
V21' The CPU detects the positive transition of V21 and measures the time (tpF) to the next
positive transition
of 13' This time is used in calculating power factor.
Figure 16. jA-SPM power factor sensing

SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
a phasor diagram depicting the relationship of voltage and
current for various power factors.
The CR192 automatically suppresses power factor until
the programmed set-point "FCX" times out. The CR192 can be
programmed
to suppress power factor trip action if the line
current is less than 50 percent activate the PF Protection. A
value of "2"
in Parameter 10 gives the above feature with the
"Ride Thru" mode. A value of "3"
in Parameter 10 provides the
above described feature with "Resync" mode operation. The
normal "Ride Thru" modes (0
in Parameter 10) and "Resync"
mode
(1 in Parameter 10) are described in Section 4.1.3.2.
Sequence
V.-V,V,
V:,=v;-V,
V.----~~
V;
V,
I, ___
l
~~-: is same
_
~hase as VI
V,
1-
j
Unity P F
V, V2 V, -
PHASE-TO-NEUT.
VOLTAGES.
, 13 -PHASE 3
V2 CURRENT
_V}
-V.
I ,
,
V. ~
I
I] LAGS V,
V1
-~
J
/
IJ ~/
90' Lag
I; t~~EADS V,
V, \
--.l
90' Lead
Figure 17. Phasor diagram description of power factor sensing
from voltage across two phases
and current in third
phase
4.1.3.2 Controller action during pull-out
If excessive mechanical load is applied to the motor shaft
during normal running of the motor
in synchronism, the resulting
lagging power factor and/or line current surge will
be detected
by the IlSPM.
Two forms of pull-out protection are available.
They are as follows.
1. Resync mode. Resync mode operation will cause the
IlSPM Field Application Relay, FAR, to act to remove the motor-
field excitation. Action will occur from either lagging power factor
below the programmed set-point, or a line current surge above
approximately four times motor full-load current. See Figure 20A.
Relay FCX drops out at the same time as
FAR. Load is
removed if an automatic loader is connected.
The motor will continue to run with field removed for the
programmed power factor delay time, and if resynchronization
does not occur within this time, the TRIP relay will operate and
the motor will stop.
The display will indicate
"PF TRIP."
2. Ride-thru Mode. If the alternate "ride-thru" mode is
selected, the field is not removed immediately as in the resync
mode.
Instead, if the power factor dips below the trip point and
persists for the PF time delay, the TRIP relay will operate and
the motor will stop. Also, a line current surge greater than
approximately four times motor full load will cause TRIP
operation if the PF time delay is exceeded. Power factor trips
are indicated by
"PF TRIP" in the display. Line current
surges greater than four times rated line current are indicated
by
"PULL-OUT TRIP"
4.1 .3.3 Effect of voltage dips on motor power
factor
Solid-state excitation systems have an effect on the way
motor power factor responds to line voltage dips. The effect may
be to cause a power-factor relay
to operate inadvertently. This
causes the motor to trip on lagging power factor caused by a
transient condition which is not
an actual pull-out condition.
A solid-state exciter differs from a rotating exciter
in the way
it responds to voltage dips. The rotating inertia of a Motor-
Generator set may maintain excitation voltage relatively
constant for several seconds, but a solid-state exciter has
practically no built-in delay in the way it responds to line voltage.
Therefore, any delay in change of motor-rotor flux following an
excitation voltage change is determined by the time constant of
the rotor field poles themselves. This
is usually 0.5 to 1.0
seconds.
The sequence of events transpiring during a voltage dip
with a solid-state exciter
is depicted in Figure 18. Assuming the
condition of a line voltage decrease of
15 percent with the motor
initially at unity power factor, the power factor will swing leading
momentarily because the generated EMF does not change until
the rotor flux decreases (determined by field time constant) and
the motor will tend to maintain constant horsepower by slightly
increasing line current. As the field flux decreases, generated
EMF also decreases, and the power factor will move back
towards unity, and there will be a load angle increase to permit
motor torque to be restored to that required to drive the load.
During both of these sequences the motor power factor has not
become significantly lagging, so the power-factor relay does not
operate.
Finally, when line voltage comes back to normal, the power
factor will momentarily swing over to lagging and the power
factor protection relay will trip because the rotor flux does not
respond as rapidly to change as the stator, and generated EMF
15

GEH-5201, Synchronous-motorControl
SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
ex: = Load Angle
<D Motor At Unity PF
Normal Load lARA
Parallel With Line
Volts
IA
® Motor PF Swings
Leading When Line
Voltage
Drops And Excitation
Remains
Constant (Due To Fld
Time Const.)
IA VLine Motor Does Not Pull
Out
PF Approx 1.0
IAXA
_<Dt®
Power
Factor
Lead
0.7
t 0.8
0.9
1.0
1 0.9
0.8
0.7
Lag 0.6
0.5
0.4'---------'----'------
16
@ Motor PF
Becomes Slightly lARA
Lagging When
Excitation Drop
Equals Line Drop
VLine
~
IA
EG IAXA
~~g)
@) Motor PF Dips A A
Heavily Lagging When EG -Generated EMF
Line Voltage Is IA -Line Amperes
Restored
RA -Armature Resistance
XA -Arm Reactance
o 0.5 1.0 1.5
Time-Seconds
Figure 18. Motor power factorresponse to line voltage variances
2.0

SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
is low relative to line volts for a time period long enough to
operate the relay.
A power-factor device with a 1.O-second built-in time delay
should remain unaffected by these changes.
4.1.3.4 Power factor detection and indica-
tion when
motor is driven by over-hauling
load (generating)
Many synchronous motor applications require that the
motor operate with
an overhauling load (in generating mode).
The power factor protection must be able to provide pull-out
protection during overhauling load conditions.
The CR192 JlSPM provides pull-out protection for the
synchronous motor operating in both the generating and the
motoring mode. However, conventional power-factor detection
and indication for motors and generators are opposite. Simply,
the convention is that a motor has a leading power factor when it
is
overexcited (producing reactive power). A generator, by
convention, is leading power factor when it is
underexcited
(consuming reactive power). In order to understand this differ-
ence, it is necessary to recognize that the definition of a motor
voltage reference phasor is 180 degrees displaced from its
corresponding conventional generator voltage reference phasor.
VAB = VA -VB (Conventional
Motor Phasor)
Therefore, a given line current that leads the conventional
generator voltage phasor will lag the corresponding conven-
tional motor phasor. Figure 19 shows that IA is lagging V AB
(conventional motor phasor) while it is leading V
BA
(conven-
tional generator phasor).
This confusion can be eliminated by defining one terminal
voltage phasorfor both generating and motoring modes. Simply,
ifV AB is used as the reference phasor, then the leading power
factor is always when the synchronous machine is producing
reactive power and lagging power factor when it is consuming
reactive power.
This is the approach that is taken with the
PF display for the
CR192 JlSPM. When the motor/generator is producing reactive
kVA the sign of the power factor is displayed plus (+ ), indicating
leading power factor, regardless of the operating mode. When it
is consuming reactive
kVA the sign of the power factor is
displayed negative (-).
Therefore, whetherthe machine is motoring or generating,
pull-out protection is provided by limiting the degree of lagging
power factor (under excitation) as detected by the JlSPM.
The power-factor regulation option also performsto force
the field in advance of a pull-out condition regardless of whether
the machine is operating
as a motor or a generator.
VBA = VB -VA (Conventional
Generator Phasor)
VBA ~ • VAB
IA LEADSV~ IALAGSVAB
IA Generating Mode
VA, VB -LOAD
TERMINAL
VOLTAGE
IA -LOAD
CURRENT
PHASOR
Figure 19. Powerfactor sensing -motormode versus generatormode
17

GEH-5201, Synchronous-motorControl
SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
L1
L2
L3
Voltage
Input
Main
Contactor
PF
Current
Input
PF
Detection
Feed-
Back
PF
Set-point
DC
Supply to
f Motor Field
t'"
fl
SPM
PF
Regulator
Reg
Gain
Field 1
Contactor
SCR
Propor-
tional
Exciter
Control
Signal
Figure 20. Powerfactor regulator -functional block diagram
4.2 Specifications
4.2.1 Operating temperature
Operating temperature range: 0 to 55 C (-40 C to 70 C
storage). Relative humidity zero to ninety (0-90) percent (non-
condensing).
4.2.2 Power source
The control voltage range of operation on the standard unit
is +15% to -35% rated voltage, and 50 or 60 hertz ±3 hertz,
25 VA.
Range for 115 VAC is 75 V min. to 132 V max.
Range for 230
VAC is 150 V min. to 265 V max.
These voltage ranges should
not be exceeded or erratic
operation may result.
18
NOTE: Since the potentialinput for the power factor
detection
is derived from the control power input (V1
and V2,l, itis imperative that the voltage input be
taken from the two proper motor phases. See Typical
Elementary Diagram (Figure 10) to determine
proper
phases.
4.2.3 Relay outputs
The three relay outputs (TRP, FAR, and FCX) have the
following contact ratings:
120
VAC
240VAC
Continuous
7A
7A
4.2.3.1. Relay output description
Interrupt
7A
7A
The following is a description of the relay outputs.
1. TRP -Trip Relay. This relay is normally energized
and drops out on loss of power or when the module senses
an abnormal condition.
2. FAR - Field Application Relay. This relay picks up at
the proper time to apply dc to the motor field.

SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
3. FCX - Loading Relay. This relay picks up when the
motor is fully-synchronized and ready to be loaded. It
is con-
trolled by the "FCX DELAY" programmable set-point.
4.2.4 Current transformer input
The fiSPM is designed to work from afive (5) ampere
Current Transformer
(C. T) secondary. The Current Transformer
must be connected in the proper motor phase. (See Typical
Elementary Diagram on Figure
10 to determine proper phase.)
fiSPM for brushless applications require inputs from two motor
phases. See Figure 22.
4.2.5 Power factor analog signal output
This output is a zero to ten volts dc signal corresponding to
motor power factor. Zero volts
is zero lagging power factor.
Five volts
is unity power factor, and ten volts in zero leading
power factor. Calibration: one (1) volt change corresponds to a
phase shift of eighteen (18) degrees. (Not available with power
factor regulation.). Do not connect less than 10 kilo-ohms to
this output.
4.2.6 Optional inputs/outputs
The following are the optional inputs/outputs.
1. DC Field Current Input. DC field input must be sensed
from a separately supplied D.C.C.T. (Direct Current, Current
Transformer) and C.M. (Calibration Module). These devices are
supplied automatically when field loss protection and/or the field
current display option is furnished.
Field Discharge
Voltage
Exciter Voltage
Field Current
Line Current
On/Off
Reduced
Voltage Start
Motor Trip lTRPl
Field Application FAR
Load Application FCX
Ana log
In puts
Operator
Key Pod
Relay
Outputs
2. Exciter Voltage Output Monitor. The output of the
field exciter must be connected
to the fiSPM through a
separate resistor when exciter voltage failure protection and/or
exciter voltage display
is furnished.
3. Power Factor Regulation Output. This optional output
consists of a de control signal which
is used to control an SCR
Variable Exciter output to obtain motor power factor regulation.
This pre-empts the power factor analog signal described in
Paragraph 4.2.5.
NOTE: The following paragraph applies to the
CR192
-E, and -F versions only.
If control voltage excursions occur outside the ranges
listed
in paragraph 4.2.2., a provision is available that will
allow the user
to connect an external stabilizing transformer
for operation with severe control power voltage dips. The
CR192
-E and -F versions have separate inputs for control
power and power factor reference voltage. This allows connec-
tion for control power from a stabilized voltage source of
115
VAC (CR192E), or 230 VAC (CR192F). Both of these versions
require a 6-7
VAC nominal input (unstabilized) for the power
factor reference voltage. Terminal points "V1
EXT" and
"GND" have been added to accommodate the separate PF
reference voltage. See Figure 31.
4.3 The CPU status light
The CPU status light is a bicolor type device. It should
normally glow green. If it is red continously, a problem exists
with the microprocessor or with a peripheral device. If the
Display
CPU
Status
Indication
ROM
Program
Memory
Electrically
Alterable
ROM
Motor
Parameters
Fai I Safe
(Watchdog)
Timer
Figure 20A. CR192 fiSPM blockdiagram
19
--------------~---.----

GEH-5201, Synchronous-motorControl
SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
light cannot be reset to green by depressing the recessed
pushbutton on top of the case, then the unit should be
replaced. Momentary flashes of red, particularly during power
up initialization, are normal and should
be ignored.
4.4 Non-volatile, set-point
memory
The CR192 /lSPM contains an electronically-alterable, read-
only-memory (EAROM) to retain set-point parameters through
periods of power outage without the use of a battery storage.
Also if the /lSPM is stored or left idle for long periods of time, its
set-points do not have to be re-entered prior to placing the unit
back in service.
20
4.5 Readout of module
temperature
The CR192 can display its internal temperature in
degrees Celsius.
To display the internal temperature press
"SHIFT" then the "4" key. The internal temperature of the
IlSPM will be displayed. Press any key to return the display to
normal. The temperature may be displayed while the motor is
running or stopped.
4.6 Circuit board conformal
coating
All of the printed circuit boards are now conformally
coated to help protect the board, the components, and the
soldered connections from moisture, dust, and common
atmospheric contaminants.