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3 phase induction motors running in parallel on a VS drive??

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Hello all

I hope this is the right forum.

Anyway, I am working on an applicaiton that will run 2 3 phase induction motos onto the same load / output shaft.

I am currently connecting the 2 motors in parallel onto the same VS drive.

Now, not remembering all the fine details of induction motors, I am not sure if this can actually work correctly.

I am thinking back emf , slip etc etc.

The requirement is to have each motor develop full torque / power into the load.

What are your thoughts?

Best regards

X
 

In a factory there are thousands of motors running in parallel on the same 3 phase supply! if your motors are identical enough to deliver exactly 100% full torque is some thing only the motor manufacturers could tell you. I would guess identical motors are within 3% or so.
Frank
 

chuckey said:
In a factory there are thousands of motors running in parallel on the same 3 phase supply! if your motors are identical enough to deliver exactly 100% full torque is some thing only the motor manufacturers could tell you. I would guess identical motors are within 3% or so.
Frank
Click to expand...

Hello

Yes, but this is different in that I want to run 2 motors simultaneously off the same VS drive or VFD as it is also known.

I am not sure if these drives use some sort of emf feedback from the motor to determine their output.

It would be reallyt bad if the 2 motors start competing with each other by 'telling' the drive different things.

I really don't know enough about the inner workings of these drive units but I think they are rather sophisticated.
Maybe it is not an issue and can work without any problems.
I am hoping someone can give me more advise.


Regards
X
 

Most modern VFD inverters are actually sensorless vector drives, not just simple three phase voltage sources. They try to drive a motor at constant speed, compensating the slip and enable the motor to produce maximal torque over the full speed range. They may act in an unwanted way, if the parallel connected motors are loaded with very different torque. Running the motors "onto the same load / output shaft" should work fine.

In case of unbalanced load, you should consult the inverter user manual. It may offer different control algorithms respectively reducing the drive to a thumb voltage source.
 
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FvM said:
Most modern VFD inverters are actually sensorless vector drives, not just simple three phase voltage sources. They try to drive a motor at constant speed, compensating the slip and enable the motor to produce maximal torque over the full speed range. They may act in an unwanted way, if the parallel connected motors are loaded with very different torque. Running the motors "onto the same load / output shaft" should work fine.

In case of unbalanced load, you should consult the inverter user manual. It may offer different control algorithms respectively reducing the drive to a thumb voltage source.
Click to expand...

Hello

Do you think it will be fine, even when the motor rotors are positoned out of phase relative to the stator poles?

Regards
X
 

An induction motor has no rotor poles, the rods of the squirrel cage rotor are skewed, so there's no dedicated position relative to the stator poles. A sensorless vector drive is not sensing rotor position, only speed.
 
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