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6-42 Programming MN792
Standstill Standstill logic is used to inhibit rotation during Zero Speed demand. If the drive is below the zero speed
threshold [12] and Standstill Logic [11] is enabled, the speed and current loops are quenched to prevent shaft
oscillation around zero speed. Standstill Logic is useful in maintaining absolute zero speed but can cause
problems in web handling applications using tension feedback. At zero speed, the SCR’s turn off allowing web
tension to pull the driven roll in reverse. When the drive no longer senses zero speed, the SCR’s turn on
causing forward rotation and regulate tension. An oscillation condition can result as the drive SCR’s turn on and
off trying to maintain a fixed position. A “not at standstill” signal is sent to the drive enable logic.
When Speed Feedback is less than Zero Threshold, the At Zero Speed output is On. At Zero Setpoint is on
when Speed Setpoint is less than Zero Threshold. When both At Zero Speed and At Zero Setpoint are on, At
Standstill is on to indicate the motor has stopped.
When Standstill Logic is enabled, the SCR firing circuits are disabled, the main contactor remains energized and
the Run Led stays on when the drive is at standstill. The drive remains in this state until standstill drops out (the
speed setpoint or speed feedback increase above the zero threshold value).
1 SETUP PARAMETERS
2 STANDSTILL
Standstill Logic
Zero Threshold
Source Tag
[11] Standstill Logic Disabled
Tag# Parameter Factory Setting
At Zero Speed
At Zero Setpoint
At Standstill
Speed Setpoint
from [63] Speed Loop
Speed Feedback
from [62] Speed Loop
Standstill
Not At Standstill"
To Enable circuit
Digital Output 1 (B5)97[77]
[78]
[79]
[306] Source Tag 89
89
[12] Zero Threshold 2.00%
Diagnostic
Connection
78
Parameter Descriptions
AT Zero Setpoint (Read in Diagnostics Parameters)
At zero speed demand.
Range: 0 : False
1 : True
AT Zero Speed (Read in Diagnostics Parameters)
At zero speed feedback.
Range: 0 : False
1 : True
AT Standstill (Read in Diagnostics Parameters)
At zero speed and zero setpoint.
Range: 0 : False
1 : True
Source Tag (Zero Setpoint)
Reserved parameter.
Range: 0 to 549
Standstill Logic
If true, the control is quenched (although the contactor remains in) when the speed feedback and
speed setpoint values are less than zero threshold.
Range: 0 : Disabled
1 : Enabled
Zero Threshold
Threshold level which defines zero setpoint and zero speed diagnostic outputs and also controls the
zero speed relay output.
Range: 0.00 to 100.00 %
Functional Description
Standstill logic inhibits the controller at zero setpoint and zero speed, i.e. at standstill. The main contactor
remains in and the Run LED remains on.
0%
Enabled
Speed Feedback
Speed Setpoint
Curve depends on load characteristics
Zero Treshold
Drive Enable
t
t
t
0%
0%
Standstill Logic
Disabled
Speed Feedback
2%
-2%
Enabled
Disabled
Enabled