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Registered Member #1394
Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111
This question has been bugging me for a while so here it is.
Can you run a 120v to 12v transformer backward by hooking up the 120v to the secondary and the primary would become the output? That way you could output 1.2kv, There may be insulation problems but I would never take it above 500v so I don't know how much of a problem that would be.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
The core would saturate. The low-voltage winding doesn't have enough inductance to prevent a huge current coming from the power line, and the formation of a too intense magnetic field in the core. It's not without reason that high-voltage transformers have much more turns than low-voltage transformers.
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
On a similar train of thought, can a transformer meant for 12v->120v from a inverter be run in reverse to make 12v? Its rated at something like 1.2kVA and its pretty hefty.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
The rule is simple: Don't exceed (by much) the nominal voltage of a winding, when using it as input, or the core saturates. You can connect a 12-127 transformer as 127-12, operating it at the same frequency. Using a MOT backwards (with the high-voltage winding connected to 127 V) would work, but then there is an unnecessarily high number of turns in the windings, and there is a way to make a smaller transformer with smaller losses due to the resistance of the wires.
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
Its strange how this topic was posted just as I was wondering. I think that with a MOT the HV windings might also cause excessive resistive losses cause of current draw?
Registered Member #1394
Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111
How does current limiting with a resitor reduce voltage? I thought a resistor limited current not voltage. As for input voltage limiting I was thinking that a dimmer switch could be used.
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Can you run a transformer backward?
