Chapter 5—Motor and Application
DG1 Series VFD MN040002EN—March 2014 www.eaton.com 19
Chapter 5—Motor and Application
Motor Selection
General recommendations for motor selection:
●
Use three-phase powered asynchronous motors with
short-circuit rotors and surface cooling, also called inverter
motors or standard motors for the frequency-controlled
drive system (PDS). Other specifications such as external
rotor motors, slip-ring motors, reluctance motors,
synchronous or servo motors can also be run with a
frequency inverter, but normally require additional planning
and discussion with the motor manufacturer.
●
Use only motors with at least heat class F (311°F [155°C]
maximum steady state temperature).
●
Four-pole motors are preferred (synchronous speed: 1500
min
–1
at 50 Hz or 1800 min
–1
at 60 Hz).
●
Take the operating conditions into account for S1 operation
(IEC 60034-1).
●
When operating multiple motors in parallel on one
frequency inverter, the motor output should not be more
than three power classes apart.
●
Ensure that the motor is not over-dimensioned. If a motor
in speed control mode is under-dimensioned, the motor
rating must only be one rating level lower.
Connecting Motors in Parallel
The DG1 frequency inverters allow parallel operation of
several motors using multi-pump application control mode:
●
Multi-pump application: several motors with the same or
different rated operational data. The sum of all motor
currents must be less than the frequency inverter’s rated
operational current.
●
Multi-pump application: parallel control of several motors.
The sum of the motor currents plus the motors’ inrush
currents must be less than the frequency inverter’s rated
operational current.
Parallel operation at different motor speeds can be
implemented only by changing the number of pole pairs and/
or changing the motor’s transmission ratio.
Debounced inputs may not be used in the safety circuit
diagram.
If you are connecting multiple motors on one frequency
inverter, you must design the contactors for the individual
motors according to utilization category AC-3.
Selecting the motor contactor is done according to the rated
operational current of the motor to be connected.
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