Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 160)

160 Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 3 Diagnostics and Protection
Normal Duty and Heavy Duty Operation
Applications require different amounts of overload current. Sizing a drive for
Normal Duty provides 110% for 60 seconds and 150% for 3 seconds. For a heavy
duty application, one larger drive rating than the motor is used and therefore
provides a larger amount of overload current in comparison to the motor rating.
Heavy duty sizing provides at least 150% for 60 seconds and 180% for 3 seconds.
These percentages are with respect to the connected motor rating.
Thermal Manager
The thermal manager assures that the thermal ratings of the power module are
not exceeded. The operation of the thermal manager can be thought of as a
function block with the inputs and outputs as shown below.
The following is a generalization of the calculations done by the thermal
manager. The IGBT junction temperature is calculated based on the measured
940
941
942
943
944
424
960
953
421
423
422
420
38
11
7
0
1
4
5
6
2
3
4
5
6
d14
Inverter Overload (IT)
Heatsink and
Junction Degree
Calculator
Drive Thermal Manager
Power Device Characteristics
NTC
Pwr EE Data
Duty Cycle
Drive OL Mode
PWM Frequency
DC Bus Volts
Output Current
Current Limit 1
Current Limit 2
Other Reference Sources
Current Limit Sel
Parameter
Selection
Drive OL Count
IGBT Temp Pct
IGBT Temp C
Drive Temp Pct
Drive Temp C
Active Cur Lmt
Active PWM Freq
Alarm Status B
Fault Status B
IGBT OT
Heatsink OT
Drive OL
CurLmt Reduc
PWMFrq Reduc
Drive OL
Heatsink OT
TransistorOT
SinkUnderTmp
Excess Load