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Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Arcstarter wrote;
"something i noticed is that the more load i put on the motor while running, the less current it pulls! Wicked!"
This can make sense if you consider that the load is correcting the powerfactor. Your ameter cant indicate phase angle, but if while running, you add capacitors after the ammeter, and the current drops, then the motor has a lagging power factor. You can start with about 20 ufd per amp of motor current at 60 Hz.
Registered Member #2015
Joined: Mon Mar 09 2009, 09:39AM
Location: West London
Posts: 8
I've just made a flywheel out of a bit of 3/8 inch by 5 inch diameter aluminium plate. The motor takes significantly longer to spin up. However, when it reaches synchronous speed, there is a lot of phase instability; about + -20 degrees at 1 Hz which eventually dies away after about 10 seconds (viewed with a stroboscope). In an attempt to investigate this more thoroughly ie turning the volts up and down and applying braking to the disc, I appear to have blown the diodes! Ho hum
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Your comment about milling the flats in the rotor, will turn the machine into a reluctance syncronous motor and it should run if you short all the segments of the rotor out, But it wont start. It will have to be spun to start.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
More applause for Clive! I've long thought about how to synchronize a universal motor without active feedback, but never dreamed of such an elegant solution.
On a tangent... Just stumbled upon a video about another kind of synchronous motor (permanent magnet type). This guy is playing with a microwave oven turntable motor, cranking it by hand, and gets an unexpected shock. Happens soon after 4:10 and he talks about it for the next couple minutes.
Then, most respectably, he takes the motor apart to understand the offense. See 2:00 to 3:00 here.
Reminds me of when I found a hoard of ancient telephone ringer magnetos at an estate sale. As recounted by my wife to a friend: "He turned the crank and said Ow, I just got a shock. Then turned it again and said Yes, there it goes again!"
Registered Member #2150
Joined: Tue Jun 02 2009, 08:33PM
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Posts: 29
Well I must say it's a very nice solucion. Unfortunately I can't solder the diode to my motors for some reason and the diode flies of at medium speed... I will try with some other motors, for this looks promissing!
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How To Turn A Vacuum Cleaner Motor Into A Synchronous Motor
