motor control

[tjnomad]

Have an interesting project
need to control a 24 volt DC motor with 96 volt DC series motor controller. The idea is to ramp up the voltage slowly and then pop it into 'turbo' to finish.

The first question is will the series DC motor even work (it is provided by Curtis Instruments) ? The other question is is there another off the shelf option. There is not enough money in the project for custom design.

Thanxs,
TJ

 

[itsmoked]

You have provided so little information that all that can be offered is time-wasting guesses. Why would you think a 24VDC motor would be happy with 96V? I don't understand.

 

[laundry]

tjnomad
If you can limit the output voltage to 24vdc then yes I can see no problem in this.But dont forget you must not exceed the 24cdc.Also will your controler supply the current.Also why dont you just get the correct controler.

Barry.

 

[tjnomad]

I know the 24VDC motor will not be happy that is not the issue. The question is inorder to reach the end goal the motor has to be 'overdriven' to acheive the desired speed to 'win the race'. Getting the correct controller is also part of the desired solution and where I am asking for suggestions. What other info can I offer you? Help me out here guys!
...TJ

 

[stardelta]

Putting 96 volts into a DC motor designed to operate at 24v is not a good idea regardless of what type of controller you use. You are unlikely to finish any races with a burnt out armature!!

 

[Hewlett]

Hello tjnomad,
If you need to "squeeze the max" out of the motor, and need a bigger speed range, I would suggest you rather use some type of friction gear, similar in function to that of a vespa scooter, or another variable gear.
I have no idea of the application or the lifetime you would expect from your device, but 96V is definately not recommended. I would not exeed rated voltage with more than, say, 20-30%, if I wanted to use this device more than once....
I'm not aware of any suitable controllers for you, maybe someone in Automotive > Transmission and Driveline engineering Forum would have an idea..?

 

[tjnomad]

I am aware of the fact that putting 96V's on a 24V motor is a no no, however that is the task I have been givien. I know that I need to not stress the motor over it's design criteria. What I havn't told you guys is that this is a one shot deal. The motor only needs to last a very short time and as long as it does not burst into flames or ceise up it will do the job. That is the big question can it last long enough to do the job. I can't give away too much info but the lifetime of the motor is not an issue.
thanks, TJ

 

[Skogsgurra]

A short overvoltage isn't that bad. And you can use a PWM output stage to apply 96 V pulses continuously to a 24 V armature. All you have to be careful about is not to let your D.C. get higher than about 25 percent. The mean voltage will then be 24 volts even if the pulses are 96 volts. That's the first part of it.

The second part is that you say that you need to accelerate and move very fast. And do it once. That means that you can apply a lot of overvoltage - probably 96 V for a few milliseconds - to overcome armature inductance in the first place. Then, you may keep a moderate overvoltage - say 150 to 200 percent (36 - 48 V) to accelerate up to the maximum speed the motor can take without being destroyed within a few seconds.

If I understand you right, it looks like you are doing some kind of "drag racing" with your device. That might mean that you will be accelerating all the way right onto target. And that is just as good an operational mode as anyone else. It certainly will get you there the fastest.

You need to talk to the motor manufacturer to get the limits the motor can take. Applying 96 V PWM pulses is perfectly legal. Just adjust the PWM D.C. so that the motor survives the first 98 percent of the travel. If it dies just before it hits the goal is probably of no concern since inertia will take it the few last inches (or feet - or whatever the distance might be).





Gunnar Englund

http://www.gke.org