stepper motor running at over voltage.......

[jit_singh_tara]

Dear friends,.....
i have a stepper motor 5 amp/phase , bipolar.

It was installed in a machine where it was running at 50 V(specifications said 24 volts).it was running with its own company made mosfet based driver .

Now when i am driving it with 24 volts with a stepper driver available in mkt psd6056....its max speed is much less.

please explain why this speed difference when running at 50 Volts.

by increasing the voltage supplied to stepper motor can we attain higher speed,if yes then at what cost like torque etc....what is the voltage limit that can be applied.


Any suggestions are welcome........

 

[FvM]

Yes you can considerably speed up a stepper motor when you operate it current controlled with a PWM H-bridge. The maximum voltage is mainly limited by the winding's isolation strength, but up to 100 or 120V are quite common in industrial applications. The only disadvantage is in the required hardware effort.

 

[jit_singh_tara]

thanks fvm....
You have been a genius ,coz everytime i get a logical and appropriate reply from your side....
please check out this driver psd6056 Motion Solution and let me know that by increasing supply voltage from 24 volts which i am currently giving,to 50 V will i be able to run it at higher speed.

Thanks in advance.

 

[FvM]

by increasing supply voltage from 24 volts which i am currently giving,to 50 V will i be able to run it at higher speed

Yes, I expect this is the case.

 

[jit_singh_tara]

thanks man,tomorrow i will perform this experiment of running stepper motor with stepper drive and see the max speed or freq of motor that is achievable at 24 volts and 50 volts.

Thanks

 

[asimov]

Hi,
I think the speed of a stepper motor is less dependent on the voltage of opeartion rather it should be more dependent on the frequency with which the coils are energized!!! This should be correct as the rotor of a stepper always tries to synchronize with the rotating magnetic field of the stator coil.

Asimov

 

[FvM]

the rotor of a stepper always tries to synchronize with the rotating magnetic field

Right. The discussion is about a case, where the rotor "tries" but doesn't manage. If you read it more
thoroughly, you'll find the words maximum speed of the stepper motor.

 

[jit_singh_tara]

Well i have ordered a smps 48V 12.5 amp , i am waiting for it to arrive ,then i will test the stepper motor with 48 V.

Currently i am able to get around 4.5 rev per second,i.e around 850 pulses per second .only 833 Hz freq.(24V dc power supply).
This frequency is very less,i am waiting for 48 V power supply.

Please let me know that running the motor instantaneously at high speed stalls motor,if we gradually increase the speed can we overcome this problem.I mean

Running the motor instantaneously at say 2khz will stall it.What if we slowly increase the freq or pulses /sec ,from 0 to 100 hz ,then 200 then 500 then 833hz and then go higher than this stalling position(in instantaneous mode)to 1500 Hz to 2khz.

What will be the scenario will the motor again stop at 833 hz while we are slowly increasing the freq.


thanks in advance....

 

[jit_singh_tara]

well friends ...i did the above experiment....i was able to run the motor at 4.5khz frequency . But there is a trick you just cant apply the the high freq in one go.

You have to gradually increase it from low to high .i.e to you have to implement the ramping and it runs at as high as 22.5 rev per sec . 5A/ per phase bipolar stepper motor at 48 Volts .

 

[FvM]

But there is a trick you just cant apply the the high freq in one go.

Yes. I assumed the need for acceleration/deceleration ramps to be common knowledge. Usually, there's a specified start/stopp frequency that can be applied without ramps. It decreases of course, when attaching a load with considerable inertia.