Designing a VFD for 1HP induction motor. 2

[derekpulis]

I have been tasked with designing a variable speed drive for an induction motor. What is the required (recommended) ripple for the DC voltage? This will determine my capacitor. What happens if I operate with more ripple?

I understand I need to maintain constant air-gap flux with constant voltage / frequency ratio. I don’t know why! Any good (basic) papers that cover this topic?

 

[electricpete]

here's what I know. Sorry I can't provide more info or a link:

volts/hz too high may cause overheating of the core due to saturation.

volts/hz too low will cause the torque vs slip curve to decrease... if mild this will only cause slip to increase slightly (for given freqeuncy and load), but if severe this may create the potential for a stall condition.

 

[busbar]

Posted here by others, maybe some useful info in:

http://www.nema.org/engineering/icsstandards/acadjustable.pdf

 

[cbarn24050]

Hi, look up international rectifier web site. Find the powertrain section.

 

[electricuwe]

A drive of that power is usually powered from the single phase line and using only a small DC-link capacitor is very attractive from the economic point of view.
But large ripple on the DC-Link voltage can lead to oszillations of the motor. See:

Kalker, T.; Ackva A.; Jansen, U.: "Novel Digital Controller for Induction Machines Considering Inverter Switching Times and a Fluctuating DC-Link Voltage", EPE 1991, Firenze (Conference Proceedings), p. 2-058 to 2-063

 

[derekpulis]

Thanks for everyones help!

In regard to electricuwe's response, any idea how to get a hold of the paper "Novel Digital Controller for Induction Machines Considering Inverter Switching Times and a Fluctuating DC-Link Voltage"?

 

[electricuwe]

You may find the conference proceedings in the library of a EE department of a university.EPE stands for European Conference on Power Electronic and Applications, a conference usually visited by lots of peole working in that area. If you can not get a copy post, your email-address and I can send you a copy.

 

[derekpulis]

electricuwe,

Search engines did lead me to lots of info on European Conference on Power Electronic and Applications. I wan't able to find the paper (only the abstract). It would be great if you could forward me a copy (dpulis@chamberlain.com). Thanks once again!

Any chance you will be at APEC next week? They have a couple of papers on motors. I will be there for a few.