Allen-Bradley PowerFlex 70 Reference Manual page 97

Thermal Manager Protection
The thermal manager protection 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.
Figure 20 Thermal Manager Inputs/Outputs
DTO Select
(Off,PWM,ILmt,Both)
PWM Frequency
(2 - 12 kHz)
Current Limit
(0 - 200%)
Temperature Analog Input
(Volts)
I_total V_dc
(Amps) (Volts)
Output Frequency
(0-400 Hz)
EE Power Board Data
The following is a generalization of the calculations done by the thermal
manager. The IGBT junction temperature T
drive temperature T , and a temperature rise that is a function of operating
Drive
conditions. When the calculated junction temperature reaches a maximum limit
the drive will generate a fault. This fault can not be disabled. This maximum
junction temperature is stored in EE on the power board along with other
information to define the operation of the drive thermal overload function.
These values are not user adjustable. In addition to the maximum junction
temperature there are thresholds that select the point at which the PWM
frequency begins to fold back, and the point at which current limit begins to fold
back. As T increases the thermal manager may reduce the PWM frequency. If T
J
continues to rise current limit may be reduced, and if T
drive generates a fault. The calculation of the reduced PWM frequency and
current limit is implemented with an integral control.
PWM Frequency
PWM Frequency as selected by the user can be reduced by the thermal manager.
The resulting Active PWM Frequency may be displayed in a test point parameter.
The active PWM frequency will change in steps of 2 kHz. It will always be less
than or equal to the value selected by the user, and will not be less than the drives
minimum PWM frequency. When drive temperature reaches the level where
PWM frequency would be limited, the Drv OL Lvl 1 Alarm is turned on. This
alarm will be annunciated even if the reduced PWM frequency is not enabled.
Rockwell Automation Publication PFLEX-RM001H-EN-P - June 2013
Active PWM Frequency
Active Current Limit
Drive
Drive Temperature
Thermal
Overload
IGBT Temperature
KHz Alarm
(On, Off)
is calculated based on the measured
J
continues to rise the
J
Drive Overload
DTO Fault
(On,Off)
(2 - 12 kHz)
(0 - 200%)
(x deg C)
(x deg C)
ILmt Alarm
(On, Off)
J
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