Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 161)

Rockwell Automation Publication 750-RM002B-EN-P - September 2013 161
Diagnostics and Protection Chapter 3
drive temperature and a temperature rise that is a function of operating
conditions. When the calculated junction temperature reaches a maximum limit,
the drive faults. This fault cannot be disabled. This maximum junction
temperature is stored on the power board EEPROM 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 temperature thresholds that select the points at which the PWM frequency
begins to fold back, and at which current limit begins to fold back. P960 [Alarm
Status B] alarm bits provide status as to when the fold back points are being
reached regardless of whether or not the drive is configured to fold back. Bit 6
“PWMFrq Reduc” is the alarm bit for PWM fault and is 10 °C (50 °F) below the
fault level. Bit 5 “CurLmt Reduc” is the alarm bit for current limit fold back and
is 5 °C (41 °F) below the fault level. The over temperature fault level is reduced
when running at output frequencies lower than 5 Hz.
Configuration
P420 [Drive OL Mode] lets the user select the action to perform with increased
current or drive temperature. When this parameter is set to option 0 “Disabled,”
the drive will not modify the PWM frequency or current limit. When set to 2
“Reduce PWM” the drive only modifies the PWM frequency. This is typically
used on hoisting applications. Option 1 “Reduce CLmt” only modifies the
current limit. When setting this parameter to 3 “Both-PWM 1st” the drive
modifies the PWM frequency first and then the current limit, if necessary, to
keep the drive from faulting with a F64 “Drive Overload” or F8 “Heatsink
OvrTemp” fault.
Temperature Display
The drive temperature is measured (NTC on the heat sink) and displayed as
percentage of drive thermal capacity in P943 [Drive Temp Pct] and IGBT
thermal capacity in P941 [IGBT Temp Pct]. These two parameters are
normalized to the thermal capacity of the drive, which is frame dependent, and
displays thermal usage in percent of maximum (100% = drive Trip). The heat
sink temperature, P944 [Drive Temp C], and IGBT temperature, P942 [IGBT
Temp Pct], in degrees C are also provided as test points. These cannot directly be
related to a trip point as the maximums are defined as a percent.