FIFTYGUY@xxxxxxx wrote:
In a message dated 3/13/09 6:42:25 P.M. Eastern Standard Time, bunnikillr@xxxxxxx writes:Lost me on this set up... where can I find some schematics on this type of wiring? Im still trying to understand how a 400VA trannie can handle 2.5KW load...Is the low voltage trannie added to the line voltage for 140V?It's a standard application for an autotransformer. "Buck/boost" is the industry term.
Buck boost connection can be an autotransfomer, but often isn't: the usual transformers I've used have totally separate windings; while I use autotransformer to refer to things like a variac, where it's one continuous tapped winding. Yes, they're electrically about the same.
Most buck/boost transformers are used on 120, 208, or 240 VAC circuits where the voltage isn't where it should be for one reason or another. A common application might be bringing a 208V circuit closer to 240V so a 240V device can run better. Or compensating for the voltage drop from a heavy load. Also, buck/boost transformers are *used* as auto-transformers, but they are *built* as standard isolating transformers to allow many connection options. We've used buck/boost transformers as high-current sources (up to 1500 Amps). The secondary windings tend to be terminated in lugs that stick out of the potting resin, and require bolted lugs for cable connections.
There's also often a higher insulation between pri and sec on the buck/boost than on an autotransformer.
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