Rockwell Automation 20A PowerFlex 70EC/700VC - Manual (Page 45)

Drive Overload 41
Figure 4 Thermal Manager Inputs/Outputs
The following is a generalization of the calculations done by the thermal manager.
The IGBT junction temperature T
J is calculated based on the measured drive
temperature T Drive , and a temperature rise that is a function of operating conditions.
When the calculated junction temperature reaches a maximum limit the drive will
generate a fault. This fault cannot be disabled. This maximum junction temperature
is stored on the power board along with other information to define the operation of
the drive 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.
Alarm bits within [Drive Alarm 1] provide status as to when the fold back points
are being reached (regardless of whether or not the drive is configured to fold back
or not).
“Drv OL Lvl 1” is the alarm bit for PWM fold back. “Drv OL Lvl 2” is the alarm
bit for current limit fold back.
Configuration
The [Drive OL Mode] allows the user to select the action(s) to perform with
increased current or drive temperature. When this parameter is “Disabled,” the drive
will not modify the PWM frequency or current limit. When set to “Reduce PWM”
the drive will only modify the PWM frequency. “Reduce CLim” will only modify
the current limit. Setting this parameter to “Both-PWM 1st” the drive will modify
the PWM frequency first and then the current limit if necessary, to keep the drive
from faulting with a Drive Overload or Overtemperature fault.
Temperature Display
The Drive’s temperature is measured (NTC in the IGBT module) and displayed as a
percentage of drive thermal capacity in [Drive Temp]. This parameter is normalized
to the thermal capacity of the drive (frame dependent) and displays thermal usage
in % of maximum (100% = drive Trip). A test point, “Heatsink temperature” is
available to read temperature directly in degrees C, but cannot be related to the trip
point since “maximums” are only given in %.
PWM Frequency
(2 - 12 kHz)
Output Frequency
Temperature Analog Input
(Volts)
DTO Select
(Off,PWM,ILmt,Both)
Current Limit
(0 - 200%)
Power Board Data
IGBT Temperature
(x deg C)
Drive Temperature
(x deg C)
DTO Fault
(On,Off)
Active PWM Frequency
(2 - 12 kHz)
Active Current Limit
(0 - 200%)
I_total
(Amps)
V_dc
(Volts)
ILmt Alarm
(On, Off)
KHz Alarm
(On, Off)
Drive
Thermal
Overload