Proposing to scrap some microwave ovens.
What uses are there for the power transformers?
Apparently these have 115 volt primaries and HV windings upwards of
2000 volts AC RMS.
Their power handling capacity must be of the order of 900 to 1000 VA
(volt-amps or watts)?
1000 VA at 2000 volts indicates something of the order of 0.5 amps!
Wow; 0.5 amps even at say 230 volts indicates 115 watts or thereabout
and the secondary (the 'old' primary) providing about 12 volts or
thereabouts at around 10 amps or so, provided one has a 230 volt
outlet available?
Any good (connected backwards) as a battery charger?
Ideas/criticism welcome.

On Sat, 03 Nov 2007 11:46:08 -0700, terry wrote:

Proposing to scrap some microwave ovens. What uses are there for the
power transformers? Apparently these have 115 volt primaries and HV
windings upwards of 2000 volts AC RMS.
Their power handling capacity must be of the order of 900 to 1000 VA
(volt-amps or watts)?
1000 VA at 2000 volts indicates something of the order of 0.5 amps! Wow;
0.5 amps even at say 230 volts indicates 115 watts or thereabout and the
secondary (the 'old' primary) providing about 12 volts or thereabouts at
around 10 amps or so, provided one has a 230 volt outlet available?
Any good (connected backwards) as a battery charger? Ideas/criticism
welcome.

I have seen two different designs for linear amplifiers, using microwave
oven xfrms in the HV supplies. One of the designs even removes the HV
secondary, and rewinds the transformer for the LV filiments.

Hooking them up backwards is most likely a very bad idea, as most oven
transformers have one side of their secondary tied to the core. Never a
good idea to hook up mains to such a design, due to risk of electrical
shock.

You can also use them as a Hi-Pot tester. Connect the secondary as a
voltage quadrupler to get 12 KV. Used for testing voltage breakdown. Check
oyut Hi-Pot testers. They are current limited breakdown testers.

Also make reasonable good door stops. The primary wires can be formed into
a carrying handle.

73, Colin K7FM

On Nov 3, 6:09 pm, "COLIN LAMB" wrote:
You can also use them as a Hi-Pot tester. Connect the secondary as a
voltage quadrupler to get 12 KV. Used for testing voltage breakdown. Check
oyut Hi-Pot testers. They are current limited breakdown testers.

Also make reasonable good door stops. The primary wires can be formed into
a carrying handle.

73, Colin K7FM

Thanks for idea: Yup recall using 2Kv static DC testers on gear rated
for 48 volts!

On Nov 3, 5:27 pm, Tehrasha Darkon wrote:

Hooking them up backwards is most likely a very bad idea, as most oven
transformers have one side of their secondary tied to the core. Never a
good idea to hook up mains to such a design, due to risk of electrical
shock.

Good point: I had forgotten that.
I recall the few cases I've worked on them, one end of the HV
secondary IS connected to the frame and thereby to the chassis/metal
box of the microwave! Detaching it might be dicey if insufficient
insulation from what would then become the neutral of a 115 volt
input. BUT if used, in North America on 230 volts would be (one side)
or 115 volts RMS above neutral and ground!!!!!!
Thanks for the heads up on that. Terry.

terry wrote:
Proposing to scrap some microwave ovens.
What uses are there for the power transformers?
Apparently these have 115 volt primaries and HV windings upwards of
2000 volts AC RMS.
Their power handling capacity must be of the order of 900 to 1000 VA
(volt-amps or watts)?
1000 VA at 2000 volts indicates something of the order of 0.5 amps!
Wow; 0.5 amps even at say 230 volts indicates 115 watts or thereabout
and the secondary (the 'old' primary) providing about 12 volts or
thereabouts at around 10 amps or so, provided one has a 230 volt
outlet available?
Any good (connected backwards) as a battery charger?
Ideas/criticism welcome.




I dunno about using them 'backwards'...But if you rewind the
secondary,you can get any voltage you like,and some serious current.

http://www.users.qwest.net/~ptaylor/...OTpowersupply/

Hi,

Add current limiting and there's your high current charger :-)

http://www.users.qwest.net/~ptaylor/...MOTPSpage.html

Cheers,
__
Gregg