powering a turntable AC21v engine from dismantled microwave

Thread Starter

chapeau_melon

Joined Feb 11, 2016
2
Hello,
I know I know, I've been very stupid in dismantling my microwave (the capacitor was alright don't worry)...but I forgot to take pictures nor did I sketched the wiring :(
Well, I'm trying to power an AC21V turntable engine with the parts that came from the microwave...
I'm really not that acquainted with electronics so replies have to be 'basic' :) ...
Can I power the engine with what's shown or does the transformer(ator) comes in the picture as well ?
The voltage coming out the card using connectors (N/WH/BL en L/BK/BN) is AC220V.
I do recall however that all these components where somehow connected to the engine ...

Hope you can help, many thanks in advance, have a nice day !

20160211_143525.jpg 20160211_143718.jpg 20160211_143803.jpg 20160211_143909.jpg
 

SLK001

Joined Nov 29, 2011
1,543
Don't touch the transformer (with power on it). See that blue sticker saying that its output is 5KV @ 700mA? That's enough to KILL you! Go find a transformer that gives an output of 21V or even 24V and power the motor with that.

A microwave oven is NOT a good starting point for learning electronics.
 

#12

Joined Nov 30, 2010
18,182
I don't see anything there that would produce 21 VAC. Either you are missing some parts or AC21V is a model number.

Googling around does not get me enough information to deny that it needs 21 volts AC. Why would anybody make a special voltage motor when 120/240 volt, 6 RPM motors have been available for 10 or 20 years?:confused:

Right now, I have not helped the situation.:(
 
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Lestraveled

Joined May 19, 2014
1,946
The SSM-16HR motor is listed as a 21 Vac.

Put that transformer away. It won't help you and might kill you. In fact throw everything away except for the motor.

You probably could run the motor from a 24 VAC transformer, which is readily available at electronics parts store or on line.
 

debe

Joined Sep 21, 2010
1,156
The motor is 21V ac. They are powered by a part of the cooling Fan windings used as an auto transformer configuration. See plenty wired that way these days. The fan will have 3 terminals on it.
 

ian field

Joined Oct 27, 2012
6,539
Don't touch the transformer (with power on it). See that blue sticker saying that its output is 5KV @ 700mA? That's enough to KILL you! Go find a transformer that gives an output of 21V or even 24V and power the motor with that.

A microwave oven is NOT a good starting point for learning electronics.
AFAICR: the secondary is 2kV which goes through a voltage doubler to put 4kV on the magnetron.

Whatever - its *VERY* lethal, and can jump further than mains.
 

ian field

Joined Oct 27, 2012
6,539
The Blue sticker is a 5KV 700Ma HV fuse not the transformer rating.
Some years back, a blog described how to make a radio transmitter around an oven magnetron.

The writeup described the magnetron as basically a massive 4kV Zener.

Its fed through a doubler, so the secondary is probably a little more than dead on 2kV to cover losses etc.

AFAICR: the charge pump capacitor was usually 0.9uF, so Xc is probably large relative to Rl - I'd expect the doubler to behave pretty much like a current source.
 

debe

Joined Sep 21, 2010
1,156
I guess in a Global market where you build ovens for 110v & 240V mains, every little bit you save is profit. You only need one 21v turntable motor in your parts supply instead of 2. You still need 2 different fans but just a 21v tap on each one.
 

ian field

Joined Oct 27, 2012
6,539
That's insane!
If I designed a fan that needed an extra tap on its windings to run a non-standard turntable motor my boss would fire me.

http://www.amazon.com/220V-240V-6RPM-Shaft-Synchronous-Motor/dp/B00E6R88AM
Around the 80s or so, there was a fad for adding an extra winding on record player turntable motors to power the amplifier.

Early PC PSUs often had an autotransformer so only one fan voltage was needed regardless of what voltage the rectifier (doubler) was set to.

There were all sorts of similar antics before BLDC fans became the norm.
 

#12

Joined Nov 30, 2010
18,182
I guess in a Global market where you build ovens for 110v & 240V mains, every little bit you save is profit. You only need one 21v turntable motor in your parts supply instead of 2.
Why do you need any 21 volt turntable motors when you can get 120 volt and 240 volt turntable motors without making a special fan motor (with a 21 volt winding tap)? The fan motor and the big power transformer have to match the local power voltage. What's so hard about installing a turntable motor that uses the same voltage as everything else?

What? They only have to carry the 21 volt motors if they custom wind every fan motor for 120 volts and 240 volts?
I would think custom winding a fan motor costs more than stocking 2 voltages of turntable motor...or...they could use 240 volt fan motors with a center tap and only stock one fan motor and one turntable motor.
 
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