User Manual Instruction Manual
Application Notes
13-79
13.31 Motor Overload
The motor thermal overload uses an Inverse Time (IT) algorithm to model the
temperature of the motor. The curve is modeled after a Class 10 protection thermal
overload relay that produces a theoretical trip at 600% motor current in ten (10)
seconds and continuously operates at full motor current.
Motor nameplate FLA programming is used to set the overload feature. This
parameter, which is set in the start up procedure, is adjustable from 0 - 200% of drive
rating and should be set for the actual motor FLA rating.
Setting the correct bit in Fault Config x to zero disables the motor thermal overload.
Most multimotor applications (using one drive and more than one motor) will require
the MTO to be disabled since the drive would be unable to distinguish each individual
motor’s current and provide protection.
Operation of the overload is based on three parameters; Motor NP FLA (42), Motor OL
Factor (48) and Motor OL Hertz (47).
1. Motor NP FLA (42) is the base value for motor protection.
2. Motor OL Factor (48) is used to adjust for the service factor of the motor. Within the
drive, motor nameplate FLA is multiplied by motor overload factor to select the
rated current for the motor thermal overload. This can be used to raise or lower the
level of current that will cause the motor thermal overload to trip without the need to
adjust the motor FLA. For example, if motor nameplate FLA is 10 Amps and motor
Motor Overload Curve
10
100
1000
10000
100000
100 125 150 175 200 225
250
Full Load Amps (%)
Trip Time (Seconds)
Cold
Hot