hello gyus i want to design an AC motor controller using PWM with an 220V input at 60hz. do you have any circuit relating to this problem? the flow chart as far as i study goes like this from the AC source 220V goes down to a converter that will convert AC to DC signal down to the PWM circuit then PWM Ckt is connected to an inverter that will invert DC to AC signal then an AC motor 220V input will be connected. i have already consulted someone about this and it is possible. i'm also planing to put an error correction on this to so that the Voltage reading really matches the RPM of the motor. can anyone help me with this? its for my project design in our class. thanks guys.

 

This is interesting to hear. I had always thought that AC motor control was done with a VFD circuit. I had always thought that if you ran an AC motor at a fixed frequency, the motor also ran at a fixed RPM.

So this is quite interesting. Can you send details of this PWM controlled inverter? I am sure we would all like to see it. We would need the schematic at least to figure a voltage to RPM indicator.

 

hmmmm... i still have 7 months to develop this project. after 7 months we will have an exhibit and i'm planning to present this one. i'm still figuring out how to develop the PWM of this circuit any suggestion. for sure the error correction will be attach on the AC mottor. there is a generator attach on in the voltage generated on the generator is being Feedback to the PWM circuit to see if circuit will adjust the freq. hmmm... as i have research at 60hrz the motor runs at 0-100% at 120hrz it could run from 0-200% so the significance of this study is extracting more juice on an AC motor. even let say about 150%. can you help me with this one?

 

inverter Ckt are easy to develop from DC to AC my main prob is in the PWM Ckt that will regulate the AC motor. feedback circuit will be at the end part. and another attachment to it is controlling the motor wireless. very nice design.

 

Inverters are designed to make AC from DC. Without the schematic of the inverter, though, how can anybody come up with a controlling PWM circuit?

 

so what is the first step in making this project? developing first the inverter? before the PWM circuit? what do you think?

 

I suggest a "proof of principle" experiment would be the first step. Get a small AC motor and a battery or two. Build your PWM on that scale. If your principle can be demonstrated on a 12Vac motor, it may then be scaled up easily enough.

No point in spending extra money just because "someone" said it's possible. Miscommunication happens all the time.

 

A note to the above suggestion: The AC motor you are going to try to control is an induction motor. A brush type universal motor is easily controlled by PWM, but will not demonstrate anything useful about controlling an induction motor. Experiment on a fractional horsepower AC induction motor.

 

Indeed! Kudos to Beenthere for catching my potentially expensive omission.

 

To run a pump, you will probably want to get a sine wave inverter instead of the cheaper quasi-sine or square wave products. (the non-sine wave products are inefficient for running large motor loads and also very hard on the motors). A higher input voltage are more efficient. 220V inverters are common outside the US so getting one from a non-US vendor may be cheaper. For sizing, the inverter's peak power rating must be greater than the motor's LRA (locked rotor amps) * 220. It's best to size conservatively and aim for at least 1.5X the LRA. The continuous power rating of the inverter should be at least 20% higher than the RLA (running load amps) * 220. Some surplus UPS products also have suitable inverters and can be acquired very inexpensively on ebay, particularly since the 220/240V units are obscure in the US.