Danfoss VLT 3032 User manual

1
Page
Introduction 2
Safety 2
Description of Operation 5
Sequence of Operation 9
Status Messages 11
Warning Messages 12
Alarm Messages 13
Troubleshooting Tips 17
Flow Charts 18
Symptom/Cause Charts 21
Testing the Soft Charge Circuit 23
Testing the Input Rectifiers 25
Testing the Inverter Section 26
Testing the Heatsink Temperature Sensor 27
Testing for Output Phase Imbalance 27
Testing Gate Drive Firing Circuits 28
Testing Input Rectifiers 30
Testing for Current Feedback 30
Removing and Replacing the Control Card 31
Removing and Replacing the Interface Board 31
Removing and Replacing Gate/Snubber/IGBT 32
Removing and Replacing Input Rectifiers 33
Current Limit Trips 35
Unstable Motor Operation 35
Ground Fault Trips 37
Overcurrent Trips 37
Overvoltage Trips 38
Overtemperature Trips 39
Additional Fault Codes I
Spare Parts List II
Block Diagram VLT 3032 III
Block Diagram VLT 3042 IV
Block Diagram VLT 3052 V
Table of Contents
Section Three Dynamic
Test Procedures
Section Three Static
Test Procedures
Section Two
Section One
Section Four
Section Five
Appendix

2
INTRODUCTION
The purpose of this manual is to provide technical information and
instructions that will enable the user to identify faults and affect repairs
onDanfossseries3000AdjustableFrequencyDrives,VLT3032through
VLT 3052, 230 Volt models.
Themanualhas been divided into fivesections. Thefirst section covers
the description and sequence of operations. Section two covers fault
messages and provides troubleshooting charts both in the form of flow
and symptom/cause. Section three describes the various tests and
methods used to evaluate the drives' condition. Section four covers
the removal and replacement of the various components. Section five
discusses application-specific information.
Electrostatic discharge. Many electronic components are sensitive to
staticelectricity. Voltages so lowthat they cannotbe felt, seenor heard
canreduce the life, affectperformance, or completely destroysensitive
electronic components.
When performing service, proper ESD equipment should be used to
prevent possible damage from occurring.
ESD SAFETY

3
SAFETY
WARNING:
FOR YOUR SAFETY:
The Adjustable Frequency Drive (AFD) contains dangerous voltages
whenconnectedtothe line voltage. Only acompetenttechnicianshould
carry out the service.
1) DO NOT touch the electrical parts of the AFD when the AC line is
connected.AftertheACline is disconnected wait at least 15minutes
before touching any of the components.
2) When repairs or inspection is made the AC line must be
disconnected.
3) The STOP key on the control panel does not disconnect the AC
line.
4) During operation and programming of the parameters the motor
may start without warning.ActivatetheSTOPkeywhenchanging
data.

4

5
SECTION ONE
Refer to the overall schematic in the Appendix.
It is not the intention of this manual to enter into a detailed description
of the unit's operation. Moreover, it is intended to provide the reader
withageneral view oftheunit's main assemblies. Withthisinformation,
the repair technician should have a better understanding of the unit's
operation and therefore aid in the troubleshooting process.
The VLT is divided primarily into three sections commonly referred to
as: logic, power, and interface.
The control card itself primarily makes up the logic section. The heart
of the control card is a microprocessor which controls and supervises
all functions of the unit's operation. In addition, a separate PROM
contains the parameter sets which characterize the unit and provide
the user with the definable data enabling the unit to be adjusted to
meet the customer's specific application. This definable data is then
stored in an EEPROM which provides security during power-down and
alsoallowsflexibility for future changesasneeded. Acustom integrated
circuit generates the PWM waveform which is then sent on to the
interface board for distribution to the individual gate drive circuits.
DESCRIPTION OF
OPERATION
LOGIC SECTION
Also, part of the logic section is the keyboard/display
mounted on the control card. The keyboard provides
the interface between the digital logic and the human
programmer. The LCD (Liquid Crystal Display)
provides the operator/programmer with menu
selection, unit status and fault diagnostic information.
Programming is accomplished through the use of four
of the eight keys available on the keyboard. The
additionalfourkeysprovideLocalStart,Stop,Forward/
Reverse and Jog.
A series of customer terminals are provided for the
input of remote commands such as: Run, Stop and
Speed Reference. Terminals are also provided to
supply outputs to peripheral devices for the purpose
of monitoring and control. Two programmable relay
outputsare also available to interfacetheunitwithother
devices.
In addition, the control card is capable of
communicating via a serial link with outside devices
suchas a personalcomputer ora programmable logic
controller.
The control card provides two voltages for use from
the customer terminal strip. The 24VDC is used
primarily to control functions such as: Start, Stop and
Forward/Reverse. The 24VDC is provided from a
separate section of the unit's power supply and is
delivered to the control card from the interface board
via the two conductor ribbon cable.
MICROPROCESSOR
ADRESS
DATA
RAM EPROM
EEPROM
VVC
CONTROL
POWER
POWER
FEEDBACK
ANALOG
INPUTS
ANALOG
OUTPUTS
DIGITAL
INPUTS
DIGITAL
CHANNEL
2
1
1
1
D
A
D
A
KEYBOARD
DISPLAY
RELAY

6
LOGIC SECTION
(continued) A 10VDC supply is also available for use as a speed reference when
connected to an appropriate potentiometer. These two voltage
referencesare limited in the amount of available current they can provide
(seespecifications in InstructionManual). Attempting to power devices
whichdrawcurrentsin excess of that availablemayresultinan eventual
failure of the power supply. In addition, if the supply is loaded too
heavily, sufficient voltage will not be available to activate the control
inputs.
Duringthe troubleshootingprocess it is important toremember thatthe
control card can only carry out instructions as it has been commanded.
Of course, it is possible that as a result of a failure the control card may
fail to respond to commands. For this reason lies the necessity to
isolate the fault to the control commands, the control program or the
control card itself. If, for example, the unit does not run, but yet an
obvious reason is not apparent, check for proper control signals. Has
a run command been provided on the correct terminal; and if so, has
thatterminalbeen designated as suchintheprogramming of the control
card. In addition, be sure to verify that commands are being received
by testing for the presence of voltage on the appropriate terminals.
Never assume the signal is present because it is suppose to be. If
ever in doubt of whether the remote controls are functioning properly, it
is possible to take local control of the unit to verify if the control card is
operational. Aword of caution here: prior to taking local control, insure
all other equipment associated with the drive is prepared to operate.
Inmany cases, safety interlocks areinstalledwhichcanonlybeactivated
through the use of a normal remote control start. In the same sense
thatthecontrolcardcanonlyrespondtocommands,comesthesituation
that the control card makes a response without the presence of an
actual command. By the term response, it is not meant to infer that the
control card initiates such actions as Run or Stop, but rather suggests
thatthe control card displays unknowndataoritsperformanceisaffected
as in what might be speed instability. In these cases, the first instinct
may be to replace the control card; however, in most instances, this
type of erroneous operation is usually due to electrical noise being
injected onto the remote control signal wiring. Although the control
card has been designed to reject such interference, noise levels of
sufficient amplitude can, in fact, affect the performance of the control
card.
Asmentioned,sufficientlevels of electricalnoise can cause suchthings
asspeedfluctuationsasaresultofinterferencewiththespeedreference
or with the operation of the microprocessor. In these situations it is
necessary to investigate the wiring practices of the installation. For
example,arethecontrolsignalwiresrunningin parallel with other higher
voltage signals such as the input or output power wiring? As wires are
passedin close proximity to oneanother, voltagesare induced through
capacitiveor inductive coupling. Thistype ofproblem can becorrected
by rerouting the wiring or through the use of shielded cable. When
employingtheuse of shielded cable,itisimportant to properly terminate
the drain wire. The drain wire is terminated only at the control card end
of the wire. Specific terminals are designated for this purpose. The
opposite end of the shielded cable drain wire is then cut back and
taped off to prevent it from coming in contact with ground or acting as
an antenna.

7
LOGIC TO POWER
INTERFACE The logic to power interface isolates the high voltage components of
the power section from the low voltage signals of the logic. This is
accomplishedbyuseoftheinterfaceboard. Allcommunicationbetween
the control logic and the rest of the unit passes through the interface
board. Thiscommunication includes: feedbackfromthecurrentsensors,
input from the heatsink temperature sensor, line voltage monitoring,
DC Bus voltage monitoring, control of the fans , control of the input
thyristor rectifiers and control of the gate drive firing signals. Also on
the interface board is the power supply which provides the unit with
low voltage power such as 24VDC, 16VDC, 13VDC and 5VDC. The
power supply is a Switch Mode Power Supply (SMPS). The switch
mode type supply is used due to its efficiency and linearity. Another
benefit of the switch mode supply is that it obtains its power from the
DC Bus; in the event of a power loss the power supply remains active
for a longer period of time versus conventional power supplies.
Duringthe troubleshooting processit is important todetermine whether
the interface board is receiving or sending the signal that appears to
be at fault. For example, the loss of a gate-drive signal is a waveform
generated by the interface board and conversely a heatsink over-
temperature fault is a result of the interface board receiving an input
from the heatsink temperature sensor. If the signal is of the later type
(received), it is then necessary to isolate the fault to either the sending
deviceorthe interface board. Itisgenerally assumed thatacomponent
within the unit is usually at fault; and although this may in fact be the
case, it is critical to check all possibilities to avoid costly errors and
lengthy downtime. In any case, the interface board is a relatively quick
andeasy assembly to exchange; andsoifitissuspect,aquickexchange
will prove the assumption.

8
POWER SECTION The power section is made up of the SCR/Diode modules (input
rectifiers), the soft charge circuit, the DC capacitor bank, the gate drive
and snubber cards and the IGBT power devices. Also located in the
power section are the DC Bus coil, the motor coils and, although not
typicallyconsidered part ofthe powersection, the outputphase current
sensors.
During the troubleshooting process, extreme care is required when
probing into the power section components. The DC Bus, when fully
charged, can be as high as 350VDC. Although this voltage begins to
decreaseupon theremoval ofinput power, it takes up to approximately
fifteen minutes to fully discharge the DC capacitor bank. Located on
theinterface board isthe Bus Charged Indicator. The red LED isvisible
through the shield covering the lower portion of the interface board;
and as long as it is lit it indicates the DC Bus voltage is greater than
50VDC. Afault in the power section will usually result in at least one of
the incoming line fuses being blown. If one or more line fuses have
blown, itis not recommended to replacethemandreapplypowerwithout
further investigation. In a case such as this, it would be suggested to
conduct the tests listed under StaticTest Procedures in SectionThree.
These tests will result in a thorough check of all the components
operating in the power section. In addition, following the identification
and replacement of power section components, it is recommended to
disconnect the motor wires prior to reapplying power. This precaution
opens the path for short circuit currents through the motor in the case
that all faulty components have not been replaced.
R
S
T
M
3Ø
INVERTER
DC BUSRECTIFIER
SIMPLFIED PWM POWER SECTION

9
SEQUENCE OF
OPERATION
When input power is first applied, the SCR/Diode modules (input
rectifiers) are not gated so the incoming line voltage is rectified by the
softchargerectifier (BR1). As the DCBuscapacitors charge, the inrush
current is limited by the series soft charge resistors (R2 and R3).
Followingatimedelay of approximately one second,theinterfaceboard
monitorsthe DC Bus voltage and,providingithasreachedanacceptable
level, begins sending gate pulses to the SCR/Diode Modules. Once
the SCR's have been gated on, they remain in this state and the SCR/
Diode modules act as a normal rectifier. This scenario will only be
interrupted if the DC Bus fails to charge. This can be caused by
insufficient line voltage, a fault in the Power Section, a fault in the soft
charge circuit, and also by an open connection at PINS 1 and 2 of
MK15. The SCR Disable input at MK15 is provided as a means to
disable the SCR/Diode modules in the case of an external failure such
as in the Dynamic Brake option. Note that although the SCR/Diode
modulesmay be disabled,line voltageis still appliedto the unitthrough
the soft charge circuit.
Providing the charging process proceeds normally, the power supplies
will come up and provide the control card and all other sections of the
unit with low voltage control power. At this time the display in the
control card will indicate the unit is ready for operation.
Following a run command and a speed reference, the control card
delivers the PWM signals (one for each phase) to the interface board.
The interface board in turn receives these three signals and creates
the six individual gate drive pulses. The gate drive pulses are sent to
the respective gate drive circuits located on the gate drive card. From
here the output power devices (IGBTS) are switched on and off to
develop the PWM waveform which is ultimately delivered to the motor.
As the unit operates, the interface board monitors the status of the
units operating condition. Currents in excess of limits, temperatures
being exceeded, and voltages out of specification will result in the
interface board responding with a fault and sending the appropriate
fault message to the control card. When a fault occurs, the interface
board will indicate the condition via a series of LED's. The control card
will also display a fault message, and in virtually all cases trip the unit
off line. Section 2 of this manual describes the fault LED's and
messages and provides direction in determining the cause and the
solution for the fault condition.

11
SECTION TWO
FAULT INDICATORS
AND MESSAGES
STATUS MESSAGES
A variety of messages are displayed by the control card. Some of
these indicate the operational status of the unit while others provide
warnings of an impending fault. In addition, there are the alarm
messages which indicate that the unit's operation has stopped due to
a fault condition. In this section we will deal with only those messages
which interrupt the unit's operation. Acomplete list of status messages
can be found in the Instruction Manual. Along with the control card
message, the interface board contains several Light Emitting Diodes
(LED's) which aid in the identification of the fault condition.
CURRENT LIMIT
This message will flash in the display when the unit is operating above
the current limit setting as recorded in parameter 209. Parameter 310
may be set to provide a fixed time delay after which the unit will trip.
REF FAULT
This message will flash in the display should any live zero signal be
operatingoutside of its range. Forexample, 4-20ma hasbeenselected
asthe speed reference. Shouldthe currentloop be broken,the display
will flash "REF FAULT". Parameters 414 and 415 may be used to
select the unit's response to this condition.
NO 24 VOLT
This message will flash if the 24 volt power supply is missing or out of
tolerance. The 24 volt supply is used only for the customer's remote
connections.
NO MOTOR
Thismessage will flashif Motor Check hasbeen activated inparameter
313, terminal 27 is enabled and no motor is detected.

12
VOLTAGE LOW
This message will flash when the DC Bus voltage has fallen below the
lower limit. This is an indication of low line voltage. This is only a
warning message, however. If the condition persists, it will result in a
unit trip on "Under Voltage".
VOLTAGE HIGH
This message will flash when the DC Bus voltage has exceeded the
upper limit. This is an indication of high line voltage or regenerative
energy being returned to the bus. This is only a warning message,
however. If the condition persists, it will result in a unit trip on "Over
Voltage".
INVERT TIME
Thismessage will flashwhen the inverter ETRvalue has reached98%.
The inverter ETR begins counting up as soon as the output current
exceeds 105% of the unit's continuous current rating. At an inverter
ETR value of 100%, the unit trips on "Invert Time".
MOTOR TIME
This message will flash if Motor Thermal Protection has been activated
in parameter 315 and the motor ETR value has reached 98%. The
motor ETR value begins counting up if the motor is run at slow speed
or if the motor is consuming more than 116% of the motor's nominal
rated current as entered in parameter 107. At a motor ETR value of
100%, the unit will respond based on the setting in parameter 315. If
Trip has been selected, the unit will trip on "Motor Time".
OVERCURRENT
This message indicates at least one of the three output phases has
reached the peak current rating. In addition, the "Overcurrent" LED
(D8) on the interface board will flicker. During this time the control card
is attempting to initiate current limit. If the current rises to fast or the
control card cannot control the condition by means of current limit, the
unit will trip on "Over Current".
WARNING MESSAGES

13
Alarmmessageswill be indicatedbythe following messagesappearing
in the display and the red alarm LED being lit on the control panel. All
alarm messages result in the unit's operation being interrupted and
require a Manual orAutomatic reset. Automatic reset can be selected
in parameters 309 and 312. In addition, the message "Trip" or "Trip
Locked"willbedisplayed. If"TripLocked"isdisplayed,theonlypossible
reset is to cycle power and then perform a manual reset. Manual reset
isaccomplished by means ofthe front panelpushbutton or byaremote
contact closure on the appropriate control terminal. Remedies listed
with each alarm message give a basic description of the corrective
action which can be taken to correct the fault condition. For a more
detailedexplanation, see the Sympton/Cause sectionbeginningonpage
21 and the application section on page 35. Also note the numbers in
parenthesis by each alarm message. These are the codes which will
appearin the Faultmemory, Parameter602.SeeAPPENDIXIfor more
on the Fault memory.
INVERTER FAULT (1)
This message indicates a fault in the power section of the unit. This
message may also be displayed if the unit has detected a phase loss
on the input. If a phase loss has been detected, the "Loss of Phase"
LED (D9) on the interface board will be illuminated and the "Inverter
OK" LED (D4) on the interface board will be out. This fault returns a
"Trip Locked". Also see Testing The Inverter Section, page 26.
OVER VOLTAGE (2)
This message indicates the DC Bus voltage upper limit has been
exceeded. Inaddition,the"High Bus Voltage"LED(D5) on the interface
boardwillbeilluminated and the "Inverter OK"LED(D4)onthe interface
board will be out. This fault can be caused by high line voltage or
regenerative energy being returned from the motor. To remedy this
fault condition, reduce the line voltage or extend the Decel Ramp. This
fault returns a "Trip". Also see Over Voltage Trips, page 38.
UNDER VOLTAGE (3)
This message indicates the DC bus voltage has fallen below the lower
limit. In addition, the "Low Bus Voltage" LED (D6) on the interface
boardwillbeilluminated and the "Inverter OK"LED(D4)onthe interface
board will be out. To remedy this fault, increase the line voltage to the
correct value for the unit rating. This fault returns a "Trip". Also see
Testing The Soft Charge Circuit, page 23.
OVER CURRENT (4)
This message indicates a short circuit on the output of the inverter.
This fault may also be caused by the unit reaching the peak current
rating too rapidly for the unit to respond with current limit. An example
may be closing an output contactor with the unit at speed and a high
inertia load. The "Overcurrent Trip" LED (D7) on the interface board
will be illuminated and the "Inverter OK" LED (D4) on the interface
board will be out. To remedy this fault, check the output wiring and
motor for short circuits. This fault returns a "Trip Locked". Also see
Over Current Trips, page 37.
ALARM MESSAGES

14
GROUND FAULT (5)
Thismessageindicatesaleakagetogroundontheoutputoftheinverter.
The "Ground Fault Trip" LED (D2) on the interface board will be
illuminated and the "Inverter OK" LED on the interface board will be
out. This fault will also be present if the programming card on the
interface board is not installed. To remedy this fault, check the output
wiring and motor for ground faults. This fault returns a "Trip Locked".
Also see Ground Fault Trips, page 37.
OVER TEMP (6)
Thismessageindicates that the unit'sheatsinktemperature or the unit's
internal ambient temperature has exceeded permissible limits. This
fault may also be caused by a trip received from the optional external
temperature sensor if a sensor has been connected to terminal MK15
on the interface board. The interface board LED's indicate the nature
of the specific trip. In all cases below the "Inverter OK" LED will be out.
"Over Temperature Trip" LED (D3) only indicates the unit's heatsink
sensor has caused the trip. "Over Temperature Trip" LED (D3) and
InternalOverTemperature"LED(D109)illuminatedindicatesthe thermal
sensor located on the interface board has detected high ambient
temperature within the unit and caused the trip. "Over Temperature
Trip"LED(D3)and"ExternalOverTemperature"LED(D108)illuminated
indicates the external temperature sensor has caused the trip. To
remedy this fault, correct the over-temperature condition. This fault
returns a "Trip". Also see Overtemp Trips, page 39.
INVERT TIME (7)
This message indicates the unit has delivered greater than 105% of
the unit's continuous current rating for too long (inverse time function).
Prior to this fault condition the "Invert Time" warning will be displayed.
An indication from the interface board status LED's does not apply. To
remedy this fault, reduce the motor load to at or below the unit's
continuous current rating. This fault returns a "Trip Locked". During
the trip the counter will count down. Upon reaching 90%, the "Trip
Locked" will change to "Trip".
MOTOR TIME (8)
Thismessage indicatesthe motorhas consumed greater than 116% of
the motor's nominal current rating for too long as entered in parameter
107. This fault may also be caused from running the motor at a low
speed and high current for too long a period of time. This trip will only
occurifthe "MotorThermalProtection" has been activatedinparameter
315. Prior to the trip the "Motor Time" warning will be displayed. In
addition, this fault may be displayed if an external thermistor has been
connected to input 16 and is defective, disconnected or indicating an
over-temperaturecondition. Also notethat by selecting "Thermistor" in
parameter 400 in error will result in a "Motor Time" fault. An indication
from the interface board status LED's does not apply. To remedy this
fault, reduce the load on the motor or raise the motor's speed. This
fault returns a "Trip Locked". During the trip the counter will count
down. Upon reaching 0% the "Trip Locked" will change to "Trip".
ALARM MESSAGES
(continued)

15
INTERFACE BOARD LED'S
OC (D8-YELLOW)
OCT (D7-RED)
IOK (D4-GREEN)
LBV (D6-RED)
HBV (D5-RED)
GFT (D2-RED)
OTT (D3-RED)
PSF (D1-RED)
LOP (D9-RED)
IOT (D109-YELLOW)
EOT (D108-YELLOW)
HIGH BUS VOLTAGE
HBV (D5-RED)
Indicates the DC Bus voltage upper limit has been
exceeded.
The I0K LED will be off and the control card indicates
"Over Voltage".
LOW BUS VOLTAGE
LBV (D6-RED)
IndicatestheDCBusvoltagehasfallenbelowthelower
limit.
TheI0KLEDwillbe offand thecontrolcardwillindicate
"Under Voltage".
OVER CURRENT TRIP
OCT (D7-RED)
Indicates a short circuit on the inverter output.
TheI0KLEDwillbe offand thecontrolcardwillindicate
"Over Current".
GROUND FAULT TRIP
GFT (D2-RED)
Indicates a Ground Fault on the Inverter Output.
TheI0KLEDwillbe offand thecontrolcardwillindicate
"Ground Fault".
OVER TEMP TRIP
OTT (D3-RED)
Indicatesthe heatsink temperatureis outsideof the specifiedoperating
range.
The I0K LED will be off and the control card will indicate "Over Temp".
INTERNAL OVER TEMP
IOT (D109-YELLOW)
Indicates the internal ambient temperature has been exceeded.
The I0K LED will be off and the control card will indicate "Over Temp".
ALARM MESSAGES
(continued) CURRENT LIMIT (9)
This message will be displayed if the unit has run in current limit for a
time which exceeds the setting in parameter 310. To remedy this fault,
reduce the motor's load or verify that the correct settings have been
entered in parameter 209 (Current Limit) and parameter 310 (Current
Limit Trip Delay). This fault returns a "Trip". See Current Limit Trips,
page 35.
INTERFACE BOARD LED'S

16
INTERFACE BOARD LED'S
OC (D8-YELLOW)
OCT (D7-RED)
IOK (D4-GREEN)
LBV (D6-RED)
HBV (D5-RED)
GFT (D2-RED)
OTT (D3-RED)
PSF (D1-RED)
LOP (D9-RED)
IOT (D109-YELLOW)
EOT (D108-YELLOW)
ALARM MESSAGES
(continued) EXTERNAL OVER TEMP
EOT (D108-YELLOW)
Indicates the external temperature sensor has detected an over temp
condition. If used, the sensor is connected to MK15 on the interface
board.
The I0K LED will be off and the control card will indicate "Over Temp".
POWER SUPPLY FAULT
PSF (D1-RED)
Indicates the low voltage power supplies are out of tolerance.
The I0K LED will be off.
LOSS OF PHASE FAULT
LOP (D9-RED)
Indicates one of the input phases is missing or
extremely low.
TheI0KLEDwillbe offand thecontrolcardwillindicate
"Inverter Fault".
OVERCURRENT
OC (D8)-YELLOW
Indicates the peak current of the inverter has been
exceeded.
INVERTER OK
IOK (D4) GREEN
Indicates the inverter is free of faults.

17
GENERAL
TROUBLESHOOTING TIPS Prior to diving into a repair here a few tips if followed will make the job
easier and may prevent unnecessary damage to good components.
1. First and foremost respect the voltages produced by the drive.
Always verify the presence of line voltage and bus voltage before
working on the unit. Also remember that some points in the drive
are referenced to the negative bus and are at bus potential even
though you may not expect it.
2. Never power up a unit which has had power removed and is
suspected of being faulty. If a short circuit exists within the unit
applying power is likely to result in further damage. The safe
approach is to conduct the Static Test Procedures starting on page
23. The static tests check all high voltage components for short
circuits.Thetestsarerelatively simple to make and can savemoney
and downtime in the long run.
3. Thesafest method ofconductingtests on thedriveis with the motor
disconnected. In this way a faulty component that was overlooked
or the unfortunate slip of a test probe will generally result in a unit
trip instead of a component failure.
4. Following the replacement of parts test run the unit with the motor
disconnected. Start the unit at zero speed and slowly ramp the
speedup until thespeed is at leastabove 40 Hz.Monitor the phase
to phase output voltage on all three motor terminals to check for
balance. If balanced the unit is ready to be tested on a motor. If
not, further investigation is necessary.
5. Never attempt to defeat fault protection devices within the drive.
This will only result in unwanted component damage and may
result in personal injury as well.
6. Alwaysuse factory approved replacementparts.Theunit has been
designed to operate within certain specifications. Incorrect parts
may effect the tolerence and result in further damage to the unit.
7. Read the instruction and service manuals. A thorough
understanding of the unit is the best approach. If ever in doubt
consult the factory or an authorized repair center for assistance.

18
1)
Symptom
Motor runs unevenly
5)
Symptom
Motor does not run
NO YES
4)
Verify correct settings have
been entered in Group 1
"Load & Motor"
YES NO
YES page 20
See: 9) Refer to the section Alarm
Messages page 13.
7)
Is the correct mains supply
present at R, S, T?
NO YES
Also see Section
"Applications" pg. 35
3)
See "Testing the Inverter"
Section page 26.
2)
Is the output phase to
phase voltage and current
balanced?
6)
Is the display illuminated?
8)
Are fault messages shown
in the display?
page 19
See: 18)

19
12)
Disconnect all control
signal wires on the control
card.
Does that remove the
fault?
9)
Symptom
No fault report or light in
display.
10)
Have prefuses for the VLT
adjustable frequency drive
blown, F1, F2, F3 or F4,
F5, 56?
YES NO
11)
If one or more of the fuses
F1, F2 or F3 have blown,
test the input rectifiers and
the inverter section, pages
25 and 26. If one or more
of the fuses F4, F5 or F6
have blown test the soft
charge circuit, page 23.
NO YES
13)
The fault may be caused
by a short circuit in the
control signals.
Check control wiring for
proper connection.
NO YES
15)
Test the Soft Charge
Circuit and input rectifier,
pages 23-25.
17)
Replace the Interface/ILD
card, see page 30. Does
the fault disappear?
YES NO
16)
Replace the Control Card,
see page 31. Does the
problem disappear?
Resume
operation
YES NO
Consult
factory
Resume
operation
14)
Is the DC Bus voltage OK?
Measure the DC Bus
voltage between terminals
(89) +VDC and (88) –VDC.

20
18)
Symptom
Motor stopped. Light in
display, but no fault report.
19)
Start the VLT adjustable
frequency drive by
pressing "Start" on the
control panel.
20)
Has the display locked, i.e.
it cannot be changed or is
illegible?
Correct the motor wiring
Insure motor overloads are
seset and output contactor
closed.
NO
21)
Replace the Control Card,
see page 31. If this does
not help, the fault might be
electrical noise. Check
whether the following
precautions have been
taken:
• Have shielded cables
been used?
• Are the shields correctly
terminated?
• Is the unit properly
grounded to earth?
NO YES
Consult
factory
26)
Replace the Interface/ILD
card, see page 31.
Does the motor run?
YES NO
23)
Attempt to run the VLT in
local.
SEE CAUTION at LEFT
Make the following
parameter settings:
Parameter 003 = Local
Parameter 004 = Fref.
Change by means of
+ and – keys.
Does the motor run?
22)
Has the motor been
correctly connected and
are all motor phases in
order?
YES NO
CAUTION:
Prior to running in Local,
insure all other
equipment associated
with the VLT is ready to
function or has been
isolated
25)
Replace the Control card,
see page 31.
Does the motor run?
NO
24)
Verify that the control
signals are connected to
the correct terminals and
the appropriate parameter
settings have been
entered.

21
Incorrect or missing input voltage
Incorrect or missing DC bus voltage
Remote control wiring loading the power supply
Defective Control Card
Defective Interface Board
Defective or disconnected ribbon cables
Shorted SCR/Diode module
Shorted IGBT
Shorted soft charge rectifier
Shorted DC bus
Shorted brake IGBT
Mis-wired Dynamic Brake option
Start compensation set too high
Slip Compensation set too high
Improper current feedback
PID Regulator or Auxilary Reference misadjusted
Open winding in motor
Open connection to motor
One inverter phase missing. Test output phase balance, page 27.
One half of one inverter phase missing. Test output phase balance,
page 27.
6. Motor Runs Unloaded But Stalls
When Loaded. (Motor may run rough
and VLT may trip.)
1. Control Card Display Is Not Lit.
2. Blown Input Line Fuses
3. Blown Soft Charge Fuses
4. Motor Operation Unstable (Speed
Fluctuating)
5. Motor Draws High Current But
Cannot Start. (May appear to rock
back and forth.)
SYMPTOM/CAUSE CHARTS
SYMPTOM/CAUSE charts are generally directed towards the more experienced technician. The intent of these
charts is to provide a range of possible causes for a specific symptom. In doing so, these charts provide a direction,
but with limited instruction.
SYMPTOM POSSIBLE CAUSES