4-10 Operating the Converter
590 Series DC Digital Converter
16 Adjustment for field weakening:
If the drive is to be run with a top speed greater than the base speed (usually 1500 rpm) then
`field weakening’ is used to achieve that top speed. (Refer to Chapter 9: “Control Loops” -
Field Control for a more detailed explanation.
Note: Note that the drive must be operating in Field Current Control.
Select CURRENT CONTROL on the FLD CTRL MODE IS
parameter. Also, field weakening cannot be used if you have
Armature Voltage feedback selected.
Run the drive up to base speed and check the motor volts are correct.
In the FLD WEAK VARS menu, verify that field weakening is
selected (FIELD WEAK ENABLE) and that the MIN FLD
CURRENT parameter is set appropriately. Adjust the maximum
armature 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).
17 Adjustment for reversing drives:
For reversing drives, check the maximum reverse speed.
Imbalance in reversing drives can only be corrected by adjusting the
ZERO SPD OFFSET parameter, which may be to the detriment of
operation at Zero Setpoint.
18 Re-set the MAIN CURR. LIMIT parameter to the original setting that you previously
noted. If in doubt, set it to 100% to correspond to 100% full load current (FLC).
Note: The controller cannot achieve 200% current unless the CUR LIMIT/SCALER parameter is
increased to 200% (from its default setting of 100%). Until this is done, the External
Current Clamp will limit the current to 100%, refer to Chapter 6: “Programming Your
Application” - CURRENT LOOP.
• If the current limit is set higher (maximum 200%) and the motor
runs into an overload condition, the current is automatically
reduced from the current limit level down to 110% FLC (continual
rating).
• If the motor is overloaded, the controller will reduce the current to 110% of the current
calibration. (If the motor continues to rotate it may overheat and thermal protection should
be provided).
• If the motor is overloaded and the current provided by the controller is not enough to
maintain rotation, i.e. it stalls, the controller will trip out showing STALL TRIP alarm, if
enabled.
MMI Menu Map
1
SETUP PARAMETERS
2
FIELD CONTROL
FLD CTRL MODE IS
MMI Menu Map
1
SETUP PARAMETERS
2
FIELD CONTROL
3
FLD CURRENT VARS
4
FLD WEAK VARS
FLD. WEAK ENABLE
MIN FLD CURRENT
MAX VOLTS
MMI Menu Map
1
SETUP PARAMETERS
2
CALIBRATION
ZERO SPD.OFFSET
MMI Menu Map
1
SETUP PARAMETERS
2
CURRENT LOOP
MAIN CURR.LIMIT
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