590 Series DC Digital Drive Operating the Drive
4-15
Step 15: Fine adjustments for Speed Feedback
Gradually increase the Speed Setpoints so that the value of the SPEED SETPOINT (DIAGNOSTIC menu) is at maximum. Check the shaft speed is
correct.
If fine adjustment is required adjust the calibration as appropriate to the speed feedback selection:
• Armature Voltage feedback has a +2/-10% trim, greater changes outside this range require re-setting of the calibration switches.
• Analog Tachogenerator has a +2/-10% trim, greater changes outside this range require re-setting of the calibration switches.
• The MICROTACH/Encoder should give an absolute rotational speed for which adjustment is unnecessary however the motor speed may not be the
relevant factor thus speed of rotation can be altered by simply adjusting the calibration.
Step 16: Adjustment for Field Weakening
If the drive is to be run with a top speed greater than the base speed then `field weakening’ is used to achieve that top speed.
(Refer to Chapter 5: “Control Loops” - Field Control for a more detailed explanation).
NOTE The drive must be operating in Field Current Control. Select CURRENT CONTROL on the FLD CTRL MODE
parameter. Also, field weakening cannot be used if you have Armature Voltage feedback selected.
IR COMPENSATION (CALIBRATION menu) is also used in field weakening applications to improve dynamic response and speed holding stability.
To set up IR COMPENSATION:
Set FIELD ENABLE to DISABLED (FIELD CONTROL menu) and set the MAIN I LIMIT to 50%. Start the drive with a 5% speed demand
and ensure the ACTUAL POS I LIMIT is 50% (diagnostic). This should stall the drive at zero speed and cause it to pass 50% current.
Monitor the BACK EMF diagnostic and note the value (typically anything up to 9% is normal). Stop the drive and enter twice this value into
IR COMPENSATION and repeat the test to ensure that BACK EMF then reads zero.
Run the drive up to base speed and check the motor volts scaling is correct. Note the scaled BEMF at base speed.
Tune the Field Current Controller and the Field Weakening Controller by reference to Chapter 5: “Control Loops”.
In the FLD WEAK VARS menu, verify that the MIN FLD CURRENT parameter is set appropriately. Adjust the base speed
BEMF volts to the required scaled level by setting the MAX VOLTS parameter.
Increase the speed above the base speed, checking that the armature volts remain constant whilst the field current reduces.
Gradually increase to maximum speed. Monitor the armature volts at maximum speed and trim the speed using the
appropriate control as detailed in Step 15. PROCEED WITH CARE - MAKE SMALL ADJUSTMENTS.
Trim the MIN FLD CURRENT parameter to the appropriate setting (5% lower than the field current at full speed).
MMI Menu Ma
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