Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 188)

188 Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 3 Diagnostics and Protection
Shear Pin As a default, the drive folds back when the output current exceeds the current
limit level. However, the shear pin feature can be used to instantly fault the drive
when output current exceeds a programmed amount. Additionally, the drive can
be programmed to ignore this condition during acceleration and deceleration
which often requires current that otherwise causes a shear pin fault. Also, the
condition can be ignored for a programmable amount of time.
Activating Shear Pin
To turn on either Shear Pin 1 or Shear Pin 2, configure [Shear Pin
n Actn]. This
activates the function. Selection between P435 [Shear Pin 1 Actn] and P438
[Shear Pin 2 Actn], cannot be made by a digital input. These parameters can be
set over a communication network. The options for each shear pin action are the
same. Default for each is 0 “Ignore.” The following are the settings for P435 and
P438.
• “Ignore” (0) – No action is taken.
• “Alarm” (1) – Type 1 alarm indicated.
• “Flt Minor” (2) – Minor fault indicated. If running, drive continues to
run. Enable with P950 [Minor Flt Cfg]. If not enabled, acts like a major
fault.
• “FltCoastStop” (3) – Major fault indicated. Coast to Stop.
• “Flt RampStop” (4) – Major fault indicated. Ramp to Stop.
• “Flt CL Stop” (5) – Major fault indicated. Current Limit Stop.
Ignore During Acceleration
There are situations where a fast acceleration of the motor causes the drive to
output current to the motor near or at the current limit value for shear pin and
fault the drive while in acceleration. To avoid this condition set P434 [Shear Pin
Cfg] Bit 0 “Shear1NoAcc” or Bit 1 “Shear2NoAcc” to 1 to ignore during
acceleration.
Shear Pin Level
A shear pin level must be programmed for the drive to monitor. This level, when
exceeded, starts a timer that must expire before performing the [Shear Pin
n
Actn]. This level is entered into P436 [Shear Pin 1 Level] or P439 [Shear Pin 2
Level]. The units are amps. Default is drive rated amps. Maximum is rated amps
multiplied by 1.5.