Superior Electric SLO-SYN SS2000MD4M-O User manual

INSTALLATION
INSTRUCTIONS
for
SLO-SYN®
MODEL SS2000MD4M-O
MICROSTEP
DRIVE/OSCILLATOR

Page 2SS2000MD4M-O
ENGINEERING CHANGES
Superior Electric reserves the right to make engineering refinements on all
its products. Such refinements may affect information given in instructions,
Therefore, USE ONLY THE INSTRUCTIONS THAT ARE PACKED WITH
THE PRODUCT.
RECORD OF REVISION
Revision Date Description
A5/04/98 Initial Release
B5/4/00 Revise corporate identity
© 1998, Superior Electric.

SS2000MD4M-O Page 1
TABLE OF CONTENTS
SECTION Page
THINGS TO KNOW BEFORE USING THIS
EQUIPMENT .............................................................................. 3
WARRANTY INFORMATION......................................................... 3
SECTION 1: INTRODUCTION ....................................................... 3
1.1 Using This Manual............................................................ 3
1.2 Product Features .............................................................. 4
SECTION 2: EXPRESS START UP PROCEDURE ........................... 5
SECTION 3: INSTALLATION GUIDELINES .................................... 6
3.1 Mounting ......................................................................... 6
3.2 Terminal Locations And Assignments................................. 7
3.2.1 Motor Connections................................................... 8
3.2.2 Power Input Connections .......................................... 10
SECTION 4: SPECIFICATIONS ..................................................... 11
4.1 Mechanical Specifications.................................................. 11
4.2 Electrical Specifications ..................................................... 11
4.3 Environmental Specifications.............................................. 11
4.4 Motor Compatibility ........................................................... 11
4.5 Switches and Potentiometers ............................................. 13
4.5.1 Motor Current Settings.............................................. 13
4.5.2 Automatic Current Reduction..................................... 13
4.5.3 Run Speed Source................................................... 13
4.5.4 External Speed Input Scaling..................................... 13
4.5.5 Potentiometers ........................................................ 14
4.6 Signal Specifications ......................................................... 15
4.7 Timing Considerations........................................................ 16
4.8 Indicator Lights................................................................. 18
SECTION 5: TORQUE VERSUS SPEED
CHARACTERISTICS .............................................................. 18
5.1 Motor Performance........................................................... 18
5.2 Typical Torque Vs. Speed Curves ....................................... 19
SECTION 6: TROUBLESHOOTING ............................................... 27
APPENDIX A: TROUBLESHOOTING ELECTRICAL
INTERFERENCE PROBLEMS........................................... 29

Page 2SS2000MD4M-O
FIGURE Page
3.1 Mounting Diagram................................................................. 6
3,2 Terminal Locations ................................................................ 7
3.3 Motor Wiring Configurations.................................................... 9
3.4 Typical Power Supply for a Single Unit Application..................... 10
4.1 Switch and Potentiometer Locations ........................................ 14
4.2 Suggested Methods for Control Interface.................................. 16
4.3 Timing Considerations ........................................................... 17
Typical Torque Versus Speed Curves
M061-LE08 Series and Parallel ............................................... 19
M062-LE08 Series and Parallel, M063-LE08 Series ................... 20
M063-LE08 Parallel, M091-FD8109 Series and Parallel.............. 21
M092-FD8109 Series and Parallel, KML060F08........................ 22
KML060F11, KML061F05,KML061F11 .................................... 23
KML062F07, KML062F13, KML063F07.................................... 24
KML063F13, KML091F07, KML091F13.................................... 25
KML092F07, KML092F13....................................................... 26

SS2000MD4M-O Page 3
THINGS TO KNOW BEFORE USING THIS EQUIPMENT
•Only qualified personnel should install or perform servicing procedures
on this equipment.
•Before performing any work on the unit, allow at least five minutes for
the capacitors to discharge fully.
•Voltage is present on unprotected pins when the Drive/Oscillator is op-
erational.
•Motors powered by the Drive/Oscillator may develop extremely high
torque. Be sure to disconnect power to the unit before doing any me-
chanical work.
CAUTION:
The SLO-SYN®SS2000MD4M-O is designed for 24 to 40 Vdc input only
(see Section 4.2, Electrical Specifications, Page 11).
WARRANTY INFORMATION
Reconfiguration of the circuit in any fashion not shown in this manual will
void the Warranty.
Failure to follow the installation guidelines as described in Section 3 will void
the Warranty.
SECTION 1: INTRODUCTION
1.1 - USING THIS MANUAL
It is important that you understand how the SLO-SYN®SS2000MD4M-O
Drive/Oscillator is installed and operated before you attempt to use it. We
strongly recommend that you read this manual completely before pro-
ceeding with the installation of this unit.

Page 4SS2000MD4M-O
This manual is an installation and operating guide to the SLO-SYN
SS2000MD4M-O Drive/Oscillator. Section 1 gives an overview of its fea-
tures. Section 2 describes the steps necessary to place the MD4M-O into
operation. General wiring guidelines as well as the physical mounting of the
unit and connections to the drive portion are covered in Section 3.
Complete specifications, listed in Section 4, provide easily referenced infor-
mation concerning electrical, mechanical and environmental specifications.
The procedure for setting the motor current level and connection of Oscillator
I/O are also covered in this section.
Torque versus speed characteristics with all appropriate SLO-SYN Stepper
Motors are given in Section 5. Section 6, Troubleshooting, gives procedures
to follow if the Drive/Oscillator fails to operate properly.
Appendix A provides procedures for troubleshooting electrical interference
problems.
1.2 - PRODUCT FEATURES
The SLO-SYN SS2000MD4M-O Drive/Oscillator combines a bipolar,
two-phase PWM drive which uses hybrid power devices and a con-
trol/oscillator in one compact package. Micro-stepping at 1/32 step resolu-
tion (6400 pulses/revolution) is used to ensure smooth low speed opera-
tion. The maximum running speed is 3,000 rpm. Features include:
•Switch selectable motor current levels of 1.0 through 3.5 amperes
•Microprocessor-based Digital Oscillator for accurate speed control
•Built-in Potentiometers for Accel, Decel, Low Speed, and Run Speed
•Full short circuit protection (phase-to-phase and phase-to-ground)
•Undervoltage and transient overvoltage protection
•Efficient thermal design
•Windings Off capability
•User selectable Automatic Current Reduction at standstill
•Compact size
•Sturdy all-aluminum mounting base
•Run Speed Control from Built-in Potentiometer or External Voltage Input

SS2000MD4M-O Page 5
SECTION 2: EXPRESS START UP PROCEDURE
The following instructions define the minimum steps necessary to make your
Drive/Oscillator operational.
CAUTION:
Always disconnect the power to the MD4M-O before connecting or dis-
connecting the motor leads. FAILURE TO DO THIS WILL RESULT IN A
SHOCK HAZARD AND MAY DAMAGE THE DRIVE.
Always operate the Drive/Oscillator with the Motor and unit enclosure
GROUNDED. Be sure to twist together the wires for each motor phase
as well as those for the dc input. Six twists per foot (0.3 m) is a good
guideline.
1. Check to see that the motor used is compatible with the Drive/Oscillator.
Refer to Section 4.4 for a list of compatible motors.
2. Set the correct current level for the motor being used and set the switches
per the instructions in Section 4.5.1. Heat sinking may be required to
maintain case temperature below +70 C (+158 F).
3. Select the desired motor current at standstill (50% or 100%) and set
switch #6 as described in section 4.5.2.
4. Select the appropriate run speed source (on board trim pot or external
input) and set switch #7 as described in Section 4.5.3. If an external run
speed voltage source is to be used select the appropriate voltage range
(0-5V or 0-10V) and set switch #8 as described in Section 4.5.4.
5. Wire the motor per the "Motor Connections" description in Section 3.2.
6. Connect the power source to the DC input terminal strip. Be sure to follow
the instructions for connecting the filter capacitor as described in Section
3.2, under Power Input.
7. Set the desired Accel rate, Decel rate, Low speed, and motor running
speed using the appropriate potentiometers as described in Section
4.5.5.
NOTES: If the motor operates erratically, refer to Section 5, "Torque Versus
Speed Characteristics".
Clockwise and counterclockwise directions are properly oriented when
viewing the motor from the end opposite the mounting flange.

Page 6SS2000MD4M-O
SECTION 3: INSTALLATION GUIDELINES
3.1- MOUNTING
The MD4M-O is mounted by fastening its mounting brackets to a flat surface.
Dimensions are shown in Figure 3.1. If the Drive/Oscillator assembly is
mounted against a bulkhead, be sure to apply a thin coating of thermal com-
pound (such as Dow Corning type 340 Silicone Heatsink Compound) be-
tween the Drive/Oscillator and the mounting surface before fastening the unit
in place. Do not use too much thermal compound. It is better to use too little
than too much.
Figure 3.1, Mounting Diagram
NOTE: Case temperature must not exceed +70° C (+158° F).
When selecting a mounting location, it is important to leave at least two
inches (51mm) of space around the top, bottom and sides of the unit to allow
proper airflow for cooling.
It is also important to keep the MD4M-O away from obvious electrical noise
sources. If possible, locate the unit in its own metal enclosure to shield it and
its wiring from electrical noise sources. If this cannot be done, keep the unit
at least three feet (0.9 m) from any noise sources.

SS2000MD4M-O Page 7
3.2- TERMINAL LOCATIONS AND ASSIGNMENTS
Figure 3.2 shows the terminal locations for the SLO-SYN SS2000MD4M-O
Drive/Oscillator.
Figure 3.2, Terminal Locations
Motor and Power
Supply Connector
(J2)
I/O Connector
(J1)

Page 8SS2000MD4M-O
3.2.1 - MOTOR CONNECTIONS
All motor connections are made via the 6-pin terminal strip. Terminal as-
signments are given below. Motor connections are shown in Figure 3.3.
J2 Pin Assignment
1 M1 (Phase A+)
2 M3 (Phase A-)
3 M4 (Phase B+)
4 M5 (Phase B-)
NOTE: Motor phase A is M1 and M3 and motor phase B is M4 and M5.
The motor frame must be grounded.
Cabling from the Drive/Oscillator to the motor should be done with a
shielded, twisted-pair cable. The wires for each motor phase should be
twisted together about six times per foot (0.3 m).
Superior Electric offers the following motor cable configurations. These ca-
bles have unterminated leads on both ends.
Length Part Number
10 ft (3 m) 216022-031
25 ft (7.6 m) 216022-032
50 ft (15.2 m) 216022-033
75 ft (22.8 m) 216022-034
Figure 3.3 shows the possible motor wiring configurations.

SS2000MD4M-O Page 9
*These leads must be insulated and isolated from other leads or
ground.
Circled letters identify terminals for connector motors, numbers identify those
for terminal box motors.
Figure 3.3, Motor Wiring Configurations
D
F
B
H
5
4
1
3
WHITE/
BLACK
BLACK
WHITE/
RED
RED
GREEN
MOTOR TERMINAL "M" NUMBERSMOTOR
CONNECTOR PIN MOTOR CONNECTOR PIN
4-LEAD MOTORS
D
F
B
H
5
4
1
3
GREEN
WHITE/
RED
RED
6-LEAD MOTORS
WHITE N.C.*E 2
G
*N.C. BLACK
WHITE/
GREEN
D
F
B
H
5
4
1
3
WHITE/
BLACK
WHITE/
RED
RED
8-LEAD MOTORS, SERIES CONNECTIONS
G
BLACK
A
WHITE
ORANGEE
GREEN
CWHITE/
GREEN
*
6
2
7
8
*
DRIVE PIN 1
DRIVE PIN 2
DRIVE PIN 1
DRIVE PIN 2
DRIVE PIN 1
DRIVE PIN 2
DRIVE PIN 4
DRIVE PIN 3
DRIVE PIN 4
DRIVE PIN 3
DRIVE PIN 4
DRIVE PIN 3
D
F
B
H
5
4
1
3
WHITE/
RED
RED
8-LEAD MOTORS, PARALLEL CONNECTIONS
WHITE/
BLACK
GBLACK
AWHITE
ORANGEE
C
6
2
7
8
GREEN
WHITE/
GREEN
DRIVE PIN 4
DRIVE PIN 3
DRIVE PIN 1
DRIVE PIN 2
6

Page 10 SS2000MD4M-O
3.2.2 - POWER INPUT CONNECTIONS
The dc input power is connected to terminals 5 and 6 of the 6-pin terminal
strip (J2). Terminal 5 [Vm(+)] is the power supply plus (+) connection and pin
6 [Vom (-)] is the power supply minus (-) connection.
An unregulated supply similar to that shown in Figure 3.4 is preferable.
If a regulated supply is used, it must be capable of operating with the
added filter capacitor. A switching regulated supply may not be suit-
able for use with this product. It is important that the capacitor (C1) be
connected within three feet (0.9 meter) of the input terminals. The ca-
pacitor must be of the correct value and have the proper current and
voltage parameters (see list of components below).
It is recommended that the power supply leads be twisted together using
approximately six twists per foot (0.3 m).
NOTES: (1) The cable between the filter capacitor (C1) and the MD4M-O
Drive/Oscillator should be twisted using approximately six twists per foot
(0.3 m)). Maximum wire length is three feet.
(2) Use #16 AWG or larger wire.
(3) If the power supply is grounded, it must only be grounded on the negative
side or the short circuit protection will not operate properly.
Figure 3.4
Typical Power Supply For A Single Unit Application
Components for circuit shown in Figure 3.4
F1 1.5 ampere time delay, 250 volt
R1 5 ohm surge limiter, Dale 7SS5 or equivalent
T1 130 VA, 24 Vac output
BR1 General Instrument GBPC3502 or equivalent
C1 4700 µf, 5.5 ampere 20 kHz, 63 V rated, United Chemcon
53D472F063HS6 or equivalent

SS2000MD4M-O Page 11
SECTION 4: SPECIFICATIONS
4.1 MECHANICAL SPECIFICATIONS
Size
(Inches).................. 1.56 H x 4.13 W x 3.25 D
(mm)...................... 40 H x 105 W x 83 D
Weight.......................... 10.3 ounces (292 grams)
4.2 ELECTRICAL SPECIFICATIONS
DC Input Range............. 24 Vdc min., 40 Vdc max.
DC Current.................... see Motor Table
Drive/Oscillator Power Dissipation
(Worst Case)........... 35 watts
4.3 ENVIRONMENTAL SPECIFICATIONS
Temperature
Operating.......... +32 °F to +122 °F
(0° C to +50° C) free air ambient, Natural Convection.
Maximum heat sink temperature of 158 °F (70 °C) must
be maintained. Forced-air cooling may be required.
Storage ............ -40° F to +167° F
(-40° C to +75° C)
Humidity ................. 95% max. noncondensing
Altitude .................10,000 feet (3048 m) max.
4.4 MOTOR COMPATIBILITY
Motor Types ..................... Superior Slo-Syn M and KM Series
M Series Frame Sizes ....... M061 (NEMA 23D) through M092 (NEMA 34)
KM series frame sizes ....... KML060 (NEMA 23) through
KML092 (NEMA 34)
Number of Connections .... 4, 6, 8
Minimum Inductance......... 0.5 millihenry
Maximum Resistance........ = 0.25 x Vdc Supply/I Setting
Example:
Vdc = 30 I Setting = 3.5
R max. = 0.25 x 30/3.5 = 2.1 ohms
NOTE:..............Maximum resistance is total of motor plus cable.
CAUTION: Do not use larger frame size motor than those listed, or the
Drive/Oscillator may be damaged. If a larger frame size motor must be
used, consult the factory for recommendations.

Page 12 SS2000MD4M-O
MOTORS FOR USE WITH THE
SS2000MD4M-O DRIVE/OSCILLATOR
Power Supply Current
Motor Winding Connection Current
Setting
(Amperes) Standstill
(Amps. DC) Maximum (Amps. DC)
M061 08 Series 2.5 1.0 2.0
M061 08 Parallel 3.5 1.0 2.0
M062 09 Series 3.0 1.0 2.5
M062 09 Parallel 3.5 1.0 3.5
M063 09 Series 3.0 1.5 2.0
M063 09 Parallel 3.5 1.0 3.5
M091 09 Series 3.0 1.0 1.5
M091 09 Parallel 3.5 1.5 3.0
M092 09 Series 3.0 1.5 2.0
M092 09 Parallel 3.5 1.0 3.0
KML060F08
- - 3.5 1.0 2.0
KML060F11
- - 3.5 1.0 2.0
KML061F05 - - 2.5 1.2 1.5
KML061F11 - - 3.5 1.0 3.0
KML062F07 - - 3.0 1.0 2.5
KML062F13
- - 3.5 1.0 4.0
KML063F07
- - 3.0 1.5 2.0
KML063F13 - - 3.5 1.0 4.0
KML091F07 - - 3.0 1.0 2.0
KML091F13 - - 3.5 1.0 4.0
KML092F07
- - 3.0 1.5 2.5
KML092F13
- - 3.5 1.0 4.0
Power supply currents shown are measured at the output of the rectifier
bridge in Figure 3.4.
M061, M062 and M063 motors listed include LS, LE, CS, FC and FD ver-
sions. M091 and M092 motors include FC and FD versions with 6 or 8 leads.
Motors with windings other than those listed can be used as long as the cur-
rent ratings listed on the motors are not exceeded.
All KML motors listed have 4 leads.

SS2000MD4M-O Page 13
4.5 SWITCHES AND POTENTIOMETERS
4.5.1 Current Settings
The proper current setting for each motor is shown on the individual torque
vs. speed curves. Use this current level to obtain the torque shown. Switches
1 through 5 are used to select the current level. Select the desired operating
current by setting the appropriate switch to position 1 (ON). The OFF posi-
tion is labeled "0". Only one switch should be ON. If two or more switches
are ON, the one which selects the highest current level will be the active
switch. The switch designations are as follows:
Current
Switch (amperes)
None (All OFF) 1.0
11.5
22.0
32.5
43.0
53.5
4.5.2 Automatic Current Reduce Disable
When switch #6 is in the OFF position, the current at standstill goes to 50%
of the selected level. When switch #6 is in the ON position, the current at
standstill remains at full value.
4.5.3 Run Speed Source
When switch #7 is in the OFF position the on board speed potentiometer is
used as the run speed source. When switch #7 is in the ON position an ex-
ternal voltage applied to input "Vin" is used as the run speed source. Sec-
tion 4.5.4 provides information on the scaling of this input.
4.5.4 External Speed Input Scaling
The external speed input (Vin) scaling is selected using switch #8. Placing
switch #8 in the OFF position selects 0-5V as the range of the external
speed input. The ON position sets the input range to 0-10V.

Page 14 SS2000MD4M-O
4.5.5 Potentiometers
On board potentiometers are provided for setting the following motion pa-
rameters: Accel, Decel, Low Speed, and Run Speed. Run Speed can also
be set via:
a) external potentiometer, see Section 4.5.3.
b) external voltage input 0-5V or 0-10V, see Section 4.5.4.
This product is implemented using digital techniques. Micro-stepping at 1/32
step resolution (6400 pulses/revolution) is used to ensure smooth operation
at low speeds. The settings for Accel, Decel, Low Speed and Speed are
analog by nature and are converted to digital form using an 8-bit A/D. This
will result in granularity in the resolution settings. The ranges of each pa-
rameter are specified in Full Steps/sec. and Full steps/sec2
Parameter Description Range Resolution (8 bits)
Accel Rate at which motor
speed increases 4000 - 120,000 500 Full steps/sec2.
Decel Rate at which motor
speed decreases
4000 - 120,000 500 Full steps/sec2.
Low Speed Motor starting speed 0 - 1200 40 Full steps/sec.
Speed Motor running speed 0 - 10,000 40 Full steps/sec.
Figure 4.1, Switch and Potentiometer Locations
Switches
#Description
8External Speed Input Scaling
7Run Speed Source
6Auto Current Reduce Disable
5Motor current
4Switches 1-5
3
2
1
Potentiometers
Acceleration
Deceleration
Run Speed
Low Speed

SS2000MD4M-O Page 15
4.6 SIGNAL SPECIFICATIONS
4.6.1 I/O Terminal Assignments
All connections are made via the 7-pin terminal strip.
J1 Pin Assignment
1LOW SPEED
2DIR
3RUN
4AWO
5GND
6EXT SPEED
7+5V
4.6.2 Signal Descriptions
LOW Low Speed Input (J1-1)
SPEED When this input is activated (tied to GND) the Run Speed is set by
the Low Speed potentiometer.
DIR Direction Input (J1-2)
When this signal is high, motor rotation will be clockwise. Rotation
will be counterclockwise when this signal is low.
RUN Run Input (J1-3)
When this signal is low the motor will run in the direction set by
the DIR input at the desired set speed.
AWO All Windings Off Input (J1-4)
When this signal is low, AC and DC current to the motor will be
zero. Caution: There will be no holding torque when the AWO
signal is low.
GND Signal ground (J1-5)
This ground point can be used for activating the discrete input
signals on pins J1-1 through J1-4 . It can also be used as a refer-
ence point for an external voltage input or in conjunction with the
+5V output (J1-7) to power an external speed potentiometer.
EXT External Run Speed Input (J1-6)
SPEED This is an optional input which can be used in place of the on
board Run Speed potentiometer. Input range can be either 0-5V
or 0-10V as defined by switch #8 described in Section 4.5.4.
+5V +5V output (J1-7)
This output is provided for powering an external speed potenti-
ometer. Pin J1-5 is used as the ground reference.

Page 16 SS2000MD4M-O
4.6.3 Level Requirements
External Speed input (EXT SPEED)
Voltage .......................................... 0 to 10 VDC
Input Impedance.............................. 100K ohms
I/O Signals
Voltage Low.................................... ≤2.0 and ≥0.0 VDC
High................................... ≥3.0 VDC
Open Circuit Input Voltage .... 5 VDC typ.
Current Logic 0 sink current.............. ≤1 mA
Suggested Methods For Control Interface
Figure 4.2
4.7 TIMING CONSIDERATIONS
NOTE: Refer to Figure 4.3.
When the RUN input is activated the motor goes from 0 speed to Low speed
either immediately or after a 50 ms delay. If the LOW SPEED input is active
the motor speed will stay at Low speed, otherwise the speed is increased to
the Run speed at the acceleration rate set via the ACCEL potentiometer.
When the RUN input is removed, the motor speed is decreased to Low
Speed at the deceleration rate set via the DECEL potentiometer. Upon
reaching Low Speed, the motor is stopped.
If selected, Auto Reduce Current takes effect 50 ms after the motor stops.
The DIR input, which determines the motor rotation direction, is sampled
when the RUN input goes active (Low/tied to GND).
+5 V
EXT. SPEED
GND
AWO
RUN
DIR
LOW SPEED
J1
J2
Vm (+)
24-40 Vdc
Vom (-)
MOTOR
*
*Optional Ext. Speed Pot.
1k to 10k ohm recommended
FAULT
LED

SS2000MD4M-O Page 17
All of the switch settings, potentiometer settings, and input signals can be
changed "On-the-Fly" with the new settings, except DIR, effective immedi-
ately.
The following diagrams depict the timing relationships between the RUN in-
put, motor speed, and motor current.
Figure 4.3, Timing Considerations
50 ms 50 ms
Run Input
Low Speed
MOTOR SPEED
Run Speed
Current
Motor Speed with
LOW SPEED input
active
Run Input
Low Speed
100%
0%
Motor Speed with
LOW SPEED input
active
SW6 (Auto Reduce Current Disable) OFF
SW6 (Auto Reduce Current Disable) ON
50%
0%
100%
Current
MOTOR SPEED
Run Speed

Page 18 SS2000MD4M-O
4.8 INDICATOR LIGHTS
"FAULT" LED, Red
Lights to indicate over current condition. This condition is caused by motor
wiring errors or a ground fault.
Recovery from an over current condition requires removing and then reap-
plying the power.
SECTION 5: TORQUE VERSUS SPEED CHAR-
ACTERISTICS
5.1 MOTOR PERFORMANCE
All stepper motors exhibit instability at their natural frequency and harmonics
of that frequency. Typically, this instability will occur at speeds between 50
and 1000 full steps per second and, depending on the dynamic motor load
parameters, can cause excessive velocity modulation or improper position-
ing. This type of instability is represented by the open area at the low end of
each Torque vs. Speed curve.
There are also other instabilities which may cause a loss of torque at step-
ping rates outside the range of natural resonance frequencies. One such
instability is broadly defined as mid-range instability. Usually, the damping of
the system and acceleration/deceleration through the resonance areas aid in
reducing instability to a level that provides smooth shaft velocity and accu-
rate positioning. If instability does cause unacceptable performance under
actual operating conditions, the following techniques can be used to reduce
velocity modulation.
1) Avoid constant speed operation at the motor's unstable frequencies.
Select a Low speed that is above the motor's resonant frequencies and
adjust acceleration and deceleration to move the motor through unst-
able regions quickly.
2) The motor winding current can be reduced as described in Section 4.5.
Lowering the current will reduce torque proportionally. The reduced en-
ergy delivered to the motor can decrease velocity modulation.