Programming D-127
DC590+ Series DC Digital Drive
STANDSTILL
Set a ZERO THRESHOLD defining when the speed setpoint is at zero to inhibit motor rotation.
The inputs to this block are SPEED FEEDBACK from the SPEED LOOP function block and SPEED
SETPOINT from setpoints.
The outputs are AT ZERO SPEED, AT STANDSTILL, and AT ZERO SETPOINT. AT ZERO
SPEED is connected to DIGOUT 1 (B5) in the default configuration. A "not at standstill" signal is sent
to the drive enable logic.
When SPEED FEEDBACK is less than ZERO THRESHOLD, AT ZERO SPEED is TRUE.
When SPEED SETPOINT is less than ZERO THRESHOLD, AT ZERO SETPOINT is TRUE.
When both AT ZERO SPEED and AT ZERO SETPOINT are TRUE, AT STANDSTILL is TRUE signalling the motor has stopped.
If AT STANDSTILL is TRUE and STANDSTILL LOGIC is ENABLED, then the speed and current loops are quenched. The SCR (Silicon Controlled
Rectifier)/thyristor firing circuits are disabled, the main contactor remains energised and the RUN LED stays on when the drive is at standstill. The
drive remains in this state until standstill drops out. That is, when the speed setpoint or speed feedback rise above the zero threshold.
STANDSTILL LOGIC is useful in maintaining absolute zero speed and aids in preventing gearbox wear due to “chattering”.
However, it can cause problems in web handling applications using tension feedback: at zero speed, the SCR/thyristors turn off allowing the web
tension to pull the driven roll in reverse. When the drive no longer senses it is at zero speed, the SCR/thyristors turn back on causing the motor to move
forward and regulate tension. An oscillation condition can result as the drives SCR/thyristors turn on and off trying to maintain a fixed position.
STANDSTILL
ZERO SETPOINT 699 -300.00 to 300.00 %
The input to the standstill function. By default this is connected to the speed demand parameter from the speed loop function block.
STANDSTILL LOGIC 11 DISABLED / ENABLED
If ENABLED, the Drive is quenched (although the contactor remains in) when the Speed Feedback and Speed Setpoint values are less than ZERO
THRESHOLD.
ZERO THRESHOLD 12 0.00 to 100.00 %
Threshold level which defines zero setpoint and zero speed diagnostic outputs and also controls the zero speed relay output.
AT ZERO SETPOINT 78 FALSE / TRUE
Logic output, TRUE when INPUT is below ZERO THRESHOLD. There is hysteresis of 0.5% on this test.
AT ZERO SPEED 77 FALSE / TRUE
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