constant torque V/hz controller code

[skills]

I am thinking about writting designing a 1 phase 120volt
inverter drive and I was wondering if anyone here had snippets of the code or algorithms that I could use to start. I'll be using the Atmel AVR in AVRBASIC and I generally only use phase control but thought it would be fun to build a real good drive this time. Thanks for your help!

 

[jraef]

Just out of curiosity, what are you doing this for, i.e. what type of 120V motor do you intend upon driving with it?

"Venditori de oleum-vipera non vigere excordis populi"

 

[skills]

Great question, I am designing a mixer for food materials such as health supplements. The motor everyone but me wanted is a large shaded pole type of motor. I may not be able to use frequency control here. Maybe you know this already?

 

[jraef]

It will work on a shaded pole motor, but that may not be the best approach to take. The "controller code" you are looking for is something that companies spend 10's of thousands of $ to develop; I seriously doubt you will find someone to let you "borrow" it for free over the internet. Then you will need to integrate it into a controller, connect that to a power module, add protection, filtering, interface, packaging hardware etc. etc. Plus if you are going to buy less than 50,000 of them, they will be expensive to build.

That said, it would still be far less expensive for you to buy something already made. For instance, many many low cost (under $100) OEM VFDs are available now that will convert 1 phase 120VAC to 3 phase 240VAC variable frequency from 1/16 to 1HP. All you would need to do is change to a 3 phase motor. Easier to reverse too if that is a desired feature in your mixer.

If you insist on sticking to a single phase shaded pole motor, a company called Anacon Systems already makes a PWM drive for them.

"Venditori de oleum-vipera non vigere excordis populi"

 

[Barry1961]

I think Anacon, or what is left of Anacon, is now Invertek. Besides that I agree with Jraef.

Barry1961

 

[skills]

I hear you guys; but, I don't know if @ my anticipated volume ~~3,500/year the economics don't commend designing one myself as opposed to relying on a 3rd party. And, while I appreciate the investment a drive manufacture has in his control program, I'm sure I've given away at least the same value commercially in the last month in 'scraps and pieces'.

I do see, in retrospect; however, that I should probably use voltage control alone with torque boost as a small vernier to vc. Thanks on the line to Anacon, I'll look at what they have available and consider buying some of their wares if they fit this. Thanks again!

 

[Marke]

Can you reliably control a single phase shaded pole motor with variable frequency? You can certainly vary the voltage, just wondering what happens in the magnetics at very low frequencies.
Best regards

Mark Empson

http://www.lmphotonics.com

 

[Skogsgurra]

Mark,

Been there. It doesn't work very well. The shorting ring gets more or less useless at low frequency. Torque drops abruptly.

I am surprised that someone wants to do this. There are many better standard methods. And motors.

For small kitchen and bath-room ventilators, we have designed very simple triac controllers that change the motor voltage and utilises the increased slip to control speed. It works quite well because of the quadratic speed/torque relation, but it will not work with a constant torque load like a mixer. Even less so if it is frequency controlled. Torque goes down the sink.