Rockwell Automation 20D PowerFlex 700S with Phase I Control Reference Manual - Manual (Page 49)

Rockwell Automation Publication PFLEX-RM002D-EN-E - August 2013 49
Detail Drive Configuration and Operation Chapter 1
The 3 second current rating assumes a duty cycle of 3 seconds on, followed by 57
seconds at 100%. This results in an average current of 102.5%.
Typically the drive will have a 60 second rating of 110% of continuous current
and a 3 second rating at 150% of the continuous current. Under normal operating
conditions, the open loop function sets this current limit to the short term
(three-second) rating. If the function detects an overload, it lowers the limit to
the continuous level. If the function is in the continuous level limit, this can be
lower than the Motor Current limit. After a period of time (typically one to three
minutes), the function returns the limit to the short term rating.
Closed Loop IT Function
The drive will also adjust the Torque Current limit level based on the values in
Parameter 358 [Iq Ref Limited], parameter 313 [Heatsink Temp] and the
thermal characteristics of the drive contained in the power EE memory. Under
normal operating conditions, the function typically sets the limit at 250% of the
continuous drive rating. If the function determines that the power device
junction temperature is approaching maximum, it will reduce this limit to the
level required to prevent additional heating of the inverter. This level could be as
low as the continuous rating of the drive output amps. If the inverter temperature
decreases, the function will raise the limit to a higher level.
Drive Overload Status
Drive Overload Status can be monitored in parameter 346 [Drive OL Status].
• Bit 0 [NTC Shorted] indicates the Negative Temperature Coefficient
(NTC) device has a short circuit.
• Bit 1 [NTC Open] indicates the NTC has an open circuit.
• Bit 2 [HS OverTemp] indicates heatsink temperature is above: 105 °C for
ratings 1.1…11.0A, 115 °C for 14…34A, 100 °C for 40…52A.
• Bit 3 [HS Pending] indicates heatsink temperature is above: 95 °C for
ratings 1.1…11A, 105 °C for 14…34A, 90 °C for 40…52A.
• Bit 4 [IT Trip] indicates the drive has exceed the 3 second rating of either
the 150% normal duty rating or 200% of the heavy duty rating.
• Bit 5 [IT Pending] indicates the drive OL integrator is at 50% of the time
out time.
• Bit 6 [IT Foldback] indicates the drive closed loop current limit is in a fold
back condition. The value of the fold back is proportional to the calculated
junction temperature.
• Bit 7 [Jnc Over Temp] indicates the junction temperature has exceeded the
maximum temperature for the power semiconductor device.
150% * 3 s + 100%*57 s
60 s
average current = ------------------------------------------- = 102.5%