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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Does overspecing transformers use extra energy? posted by amnesiac on August 7, 2014 at 09:54:51:
While your transformer might not be "enough larger" to matter.... larger transformers are more efficent. Really big ones (think electric company) are up around 99%. Little bitty (few volt-amps) might be as bad as 80%.
The only downside is room, weight, cost....which you don't care about in this case....and the need to make sure you have adequate "interuppting capacity" in your over current devices.
It works like this: We connect the secondary wires together to form a short circuit. Next we apply voltage to primary (with variac and starting at zero) until we reach the voltage where the primary draws its rated current.
Example, lets say we have a 120 volt primary rated for ten amps. Assume with the secondary shorted the primary draws ten amps with 12 volts applied to it. It is then reasoned that since it can deliver rated amps at 1/10th of its rated voltage.....at its rated voltage it can deliver 10 times its rated current into a short circuit. So your "interuppting device" must be able to "clear a fault current" of 100 amps......as in circuit breaker contscts can't weld together, fail to function, etc.
I see circuit breakers tested at work. On larger breakers the instanteous current setting is typically set at ten times the breakers rating. Nothing like seeing 20,000 amps being pushed through a 2,000 amp breaker. Don't think for one split second that a household 20 amp breaker trips instanteously at 20 amps (more like 200 amps). Even a 20 amp fast blow fuse won't.....in fact many are required to carry 20 amps for a minimum of four hours!!
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Follow Ups
- RE: Quite the opposite - Russ57 12:20:43 08/07/14 (1)
- RE: Quite the opposite - amnesiac 19:06:21 08/07/14 (0)
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