# One AC motor contoller for TWO motors?



## samborambo (Aug 27, 2008)

Parallelling AC induction motors on a single drive is common but only using V/Hz control (aka open loop control) - vector control won't work. Parallelling permanent magnet AC motors (BLDC, PMSM) will not work at all unless the motors are fixed to the same shaft and are timed correctly.

Feedback sensors such as positional encoders or RPM sensors are not used in open loop control.

With parallel ACIMs, the slowest motor will produce higher torque relative to the other motor(s). Keep this in mind in your design.

Sam.


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## yarross (Jan 7, 2009)

ORDA said:


> Can I connect 2 AC motors on 1 drive, this is for project where there are 2 AC motors that run at the same speed and direction,


Sure you can. Two motors mechanically and electrically coupled and with matched rated voltages and synchronous speeds (i.e. two identical motors) can be treated as one. Don't forget to configure your inverter for a pair (winding resistances and inductances), not single motor. It will work with one encoder or in sensorless mode.



samborambo said:


> Parallelling AC induction motors on a single drive is common but only using V/Hz control (aka open loop control) - vector control won't work.


I know at least one traction drive used in EMUs, with one FOC SVM inverter per two motors. They are not even hard-coupled, only by track.
http://www.medcom.com.pl/dl/MEDCOM_EN57AKM.pdf


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## ORDA (Jan 5, 2010)

yarross said:


> Sure you can. Two motors mechanically and electrically coupled and with matched rated voltages and synchronous speeds (i.e. two identical motors) can be treated as one. Don't forget to configure your inverter for a pair (winding resistances and inductances), not single motor. It will work with one encoder or in sensorless mode.
> 
> 
> I know at least one traction drive used in EMUs, with one FOC SVM inverter per two motors. They are not even hard-coupled, only by track.
> http://www.medcom.com.pl/dl/MEDCOM_EN57AKM.pdf


Thanks both for your answer, but I should mention that we are working with PG drives controllers (www.pgdt.com) i'am not shure of the internal technique the use but the resistance can not be programmed only the frequency, slip end voltage from the motor, the also need a encoder signal.
I think i will use two drives and connect them with the CANBUS as master and slave.
The engineer at PG drives told me that it is not possible to connect two motors on one drive, so i have to believe him.


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