Triac Switch Inductive Loads

Long story short, there are many types of AC motors, and what happens depends on what type it is. For example, a "series wound" motor (as used in "variable speed" electric drills) will work well controlled this way, but several other types won't.

On exercise tread mills they use PWM, pic cpu controlled. With a PM

90vdc motor.They use a standard inverter to go from AC to DC and then use a PWM supply to run the motor from zero to full power.

A series wound motor will usually have two brushed , often with Bakelite screw covers and will turn if you connect low voltage DC to its two leads. They also turn very fast in most applications (faster than the 3600 RPM synchronous speed of a 2 pole motor) and make considerable mechanical whine from the high speed and brushes running over commutator bars. Many AC powered hand tools from moto tools to circular saws are made with series wound motors. They vary widely in speed as their load changes.

Anyway to test if a motor is "series wound" ?, if it can't be determined from label or otherwise.

I read in sci.electronics.design that snipped-for-privacy@spamnuke.ludd.luthdelete.se.invalid wrote (in ) about 'Triac Switch Inductive Loads', on Sun, 25 Sep 2005:

Physical inspection. You have to know what to look for, lie the field coils being in series with the brushes. Very high-tech. (;-)

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

...

OK, I forgot about "proportional integral cycle" control. Then, yes, you'd use a zero-crossing 3030, and turn it on for some number of cycles, and off for some number of cycles.

That's kinda different from "phase control", which switches "on" sometime during the cycle. You can get finer control, but it screws up the waveform and you get a lot of harmonics and hash and stuff.

Hope This Helps! Rich

...

Have Fun! Rich

I read in sci.electronics.design that Rich Grise wrote (in ) about 'Triac Switch Inductive Loads', on Mon, 26 Sep 2005:

Yes, you get interharmonics (the power engineers' term for sidebands) due to the 100% amplitude modulation of the supply waveform. This WILL cause your product to fail European mains harmonic emission limits, because interharmonics are lumped together with harmonics, and the even harmonic limits are very stringent.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk