User Manual Instruction Manual

Application Notes 13-73
PWM frequency begins to fold back, and the point at which current limit begins to fold
back. As T
J
increases the thermal manager may reduce the PWM frequency. If T
J
continues to rise current limit may be reduced, and if T
J
continues to rise the drive
generates a fault. The calculation of the reduced PWM frequency and current limit is
implemented with an integral control.
13.25.4PWM 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.
13.25.5 Current Limit
Current Limit as selected by the user can be reduced by the thermal manager. The
resulting active current limit may be displayed as a test point parameter.
The active current limit will always be less than or equal to the value selected by the
user, and will not be less than flux current. When drive temperature reaches the level
where current limit would be clamped, the
Drv OL Lvl 2 Alarm is turned on. This alarm
will be annunciated even if reduced current limit is not enabled.
The active current limit is used during normal operation and during DC injection
braking. Any level of current requested for DC injection braking is limited by the Active
Current Limit.
13.25.6 Configuration
The Drive OL Mode (150) 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 and the current limit.
13.25.7 DTO Fault
For all possible settings of Drive OL Mode (150), the drive will always monitor the T
j
and T
Drive
and generate a fault when either temperature becomes critical. If T
Drive
is
less than –20° C, a fault is generated. With these provisions, a DTO fault is generated
if the NTC ever malfunctions.