Rockwell Automation SP500 AC Drive Installation and Operation Manual - Manual (Page 38)

3-10 SP500 AC Drive Installation and Operation Manual Version 3.1
If the motor will be operated below one-half of its rated speed, the motor overload
relay may not protect the motor because of reduced cooling action due to the reduced
speed. A motor thermostat, internal to the motor, should be installed to monitor the
actual temperature of the windings.
3.5.2 Multiple-Motor Applications
One drive can run two or more motors. Adhere to the following requirements to assure
correct drive operation in this case:
• When starting and stopping all the motors at the same time (using the drive for
starting and stopping), the sum of the full-load sine wave currents of all the motors
must be equal to or less than the maximum sine wave output current at the selected
carrier frequency for the drive.
• When one or more of the motors connected to the output of the drive are to start
independently (using a secondary switching device to add or remove the motor from
the circuit):
Any motor that starts or stops while the drive is running must have a current rating
less than 10% of the maximum sine wave current rating of the drive at the selected
carrier frequency.
The sum of the maximum full-load sine wave currents of all the motors connected
continuously to the drive must be less than the maximum output current rating under
all conditions.
Note that each motor requires separate thermal overload protection (for example, a
motor relay or a motor thermostat).
For example: I
FLA
+ I
FLA
+ I
FLA
= I
TLA
(Motor 1) (Motor 2) (Motor 3) (Total Load)
Where: I
TLA
<100% rated drive output at the selected carrier frequency