Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 156)

156 Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 3 Diagnostics and Protection
In a Control Logix program do not set P410 [Motor OL Actn] to 1 “Alarm.”
There is an anomaly in drives with firmware version 8.001 or earlier that prevents
an overload from being asserted in P959 [Alarm Status A] and in P937
[Condition Sts 1] Bit 2 “Motor OL.” Neither of these parameters are used under
this circumstance to initiate any programmed alarm routine.
Leaving P410 [Motor OL Actn] at one of the fault settings or Flash Updating the
drive to a firmware version greater than 8.001 resolves this anomaly. Instructions
on Flash Updating drives are provided in drive firmware Release Notes
publications.
Current Limit There are five ways that the drive can protect itself from over current or overload
situations.
Method Description
Hardware Over Current This is a feature that instantly faults the drive if the output current exceeds this value.
The value is fixed by hardware and is typically 250% of drive rated amps. The fault code
for this feature is F12 “HW OverCurrent.” This feature cannot be defeated or mitigated.
Software Over Current This protection mode occurs when peak currents do not reach the hardware over
current value and are sustained long enough and high enough to damage certain drive
components. If this situation occurs, the drives protection scheme causes an F36 “SW
OverCurrent” fault. The point at which this fault occurs is fixed and stored in drive
memory.
Software Current Limit This is a feature that attempts to reduce current by folding back output voltage and
frequency if the output current exceeds a programmable value. P422/423 [Current
Limit 1/2], selected by P421 [Current Lmt Sel], are programmable up to 150% of drive
rating. The reaction to exceeding this value is programmable with Shear Pin fault.
Enabling this parameter creates an F61 or F62 “Shear Pin n” fault. Disabling this
parameter causes the drive to use fold back to attempt load reduction.
Heat Sink Temperature
Protection The drive constantly monitors the heat sink temperature. If the temperature exceeds
the drive maximum, a F8 “Heatsink OvrTemp” fault occurs. The value is fixed by
hardware at a nominal value of 100 degrees C. This fault is generally not used for over
current protection due to the thermal time constant of the heat sink. It is an overload
protection.
Drive Overload Protection Refer to Drive Overload on page 158 .