2 Engineering
2.9 Three-phase motor
DA1 Variable Frequency Drives
08/18 MN04020005Z-EN
www.eaton.com
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2.9.3 Connecting Motors in Parallel
When in V/Hz control mode (default setting, P4-01 = 2), DA1 variable
frequency drives can be used to run multiple motors simultaneously.
Connecting motors in parallel will reduce the load resistance at the variable
frequency drive’s output. This will cause the total stator inductance to
decrease and the cables’ stray capacitance to increase. As a result of this,
the current distortion becomes greater compared to the single motor
connection.
In order to reduce the current distortion, a motor choke or sine wave filter
should be installed in the output of the variable frequency inverter
(
￫
If multiple motors are connected in parallel, the totalof their
motor currents must be lower than the DA1 variable frequency
drive’s rated operational current.
￫
When running multiple motors in parallel with a single variable
frequency drive, the individual motors’ outputs should not be
more than three output classes apart.
￫
If several motors are being run in parallel, you will not be able to
use the variable frequency drive’s electronic motor protection.
As a result, each individual motor must be protected with
thermistors and/or an overload relay.
Within a frequency range of 20 to 120 Hz, the PKE electronic
motor-protective circuit-breaker can be used for motor
protection at a DA1 variable frequency drive’s output as well.
CAUTION
For the parallel operation of several motors on one DA1 variable
frequency drive, the contactors of the individual motors must be
designed according to utilization category AC-3.
The selection of the motor contactors occurs according to the
rated operational current of the motor to be switched.
￫
The total of the motor currents in operation, plus one motor’s
inrush current, must be less than the rated operational current
of the variable frequency drive.
In applications with motors that will be connected and
disconnected, we recommend using a motor choke.
