Programming Your Application
6-81
590+ Series DC Digital Converter
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
AT ZERO SETPOINT
[ 78]
–
FALSE
AT ZERO SPEED
[ 77]
–
FALSE
AT STANDSTILL
[ 79]
–
FALSE
89
–
[306] ZERO SETPOINT
DISABLED
–
[ 11] STANDSTILL LOGIC
2.00 %
–
[ 12] ZERO THRESHOLD
MMI Menu Map
1
SETUP PARAMETERS
2
STANDSTILL
STANDSTILL LOGIC
ZERO THRESHOLD
Parameter
Tag
Range
AT ZERO SETPOINT
78
FALSE / TRUE
Refer to the DIAGNOSTICS function block description, page 6-23.
AT ZERO SPEED
77
FALSE / TRUE
Refer to the DIAGNOSTICS function block description, page 6-23.
AT STANDSTILL
79
FALSE / TRUE
Refer to the DIAGNOSTICS function block description, page 6-23.
ZERO SETPOINT
306
0 to 639
(SOURCE TAG)
Do not alter.
Reserved parameter for use by SSD Drives.
STANDSTILL LOGIC
11
DISABLED / ENABLED
If ENABLED, the Converter 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.