motor control by phase angle

[mitwrong]

Hi, Member:
Does anyone knows or has schematic about motor speed control using phase angle method, as well as Ward Leonard control method.
My motor is 1 phase, 1 hp, induction type. please help?

Mitwrong

[AndrewT]

Hi,
induction motor does NOT suit speed control.

It tries to lock onto the supply frequency.
At zero slip (and zero load) it is exactly at frequency divided by number of poles.
As load increases the slip increases.
Overload it and the slip becomes a stall just after it has overheated due to running too slow with very heavy currents in both the rotor and the stator.

edit.
does your motor have multiple tappings?
Some can be wired to different poles and thus achieve a stepped speed change, mine does 1500rpm (2pole), 750rpm(4pole),500rpm(6pole). I do not know if the maximum torque changes with the poles. I suspect the torque does NOT increase with decrease in speed settings.

[mitwrong]

Andrewt:
Thanks Ur info., My motor is 4 pole, 1500rpm at 50hz. I use this motor to drive turning lathe. I wish I could change it's speed continously with constant torque instead of changing the pulley size. it will be more convinient if with speed ctrl. I have read from books that can be use SCR/TRIAC method. Even Induction motor can also be controlled. But I don't have the schematic, thats what I wanted if other member has. anyway thanks Ur reply.

[AndrewT]

Hi,
universal motors suit speed control (the ones found in your hand tools).
Permanent magnet motors also suit speed control (the kind in slot cars and windscreen wipers).
Induction motors do not, they like to lock on to the frequency.

If you were to build a really big power amp with oscillator on the front end then you can get speed control. I don't know what range of speeds you could get from it.

If you want continuous speed control go and investigate Perbury drive. Brilliant for turning a faceplate. You can get about 10:1 out of these.

[mitwrong]

Thanks Andrew T

I think Ur right, Induction motor runs depend on frequency. That means V to F cct. May be I change to a universal motor to fit my job. I can shop around from the market.

[Eva]

The speed of synchronous motors can be controlled, all what is required is a variable frequency AC source. Square wave based solutions are easy to implement but they result in higher iron heating in the motor. Sine wave based solutions require high power high voltage class D amplifiers. Another alternative might be cycloconverters, but I don't have any reference about these.

On the other hand, I think that there are plenty of electronic speed control modules for three-phase synchronous motors in the market, and they dont require three-phase mains. You may consider going that way...

[mitwrong]

Eva,
Thanks Ur info., My motor is single phase, 1hp induction type. If it can be varies the speed by some kind of method, can U get me more info., about it. I will be highly appriciated.