Multi-motor drive of asynchronous motors

Multi-motor drive means the electrical parallel connection of several identical asynchronous motors at 1 inverter, that are rigidly and mechanically coupled and drive a load.

Parallel operation of several identical asynchronous motors is possible provided the strict compliance with the following conditions:

• Only use gearmotors of the same type and with the same winding data.
• The rotor position of the individual motors must not differ by more than the following mechanical angle:
• Z_p × Δφ_{mech_max} < 20°
• Z_p = Number of motor pole pairs
• Δφ_{mech_max} = Maximum torsion angle of the shaft connection in regard of the motor shaft
• This must be ensured by the mechanics, even for maximally different torque loads of the motor shafts.

• If encoder feedback is used, just one of the motors needs to be equipped with an encoder. This encoder must be installed on the gearmotor which has the greatest clearance or elasticity with respect to the load inertia.