I have a adjustable frequency single phase power source that goes up to 440 volts at 50Hz?

Question

I hooked up a variac and got up to 510 volts but the I need 600 volts. I was thinking about hooking up another variac in series with the first one. Would that work? It won't blow up, will it?

Answer 1

You can hook the Variacs(r) up in tandem such that the output of one is the input to the other. It would be best to make sure that the common side of the the output from the first Variac is connected to the common side of the input to the second Variac. otherwise, if the common side of the input to the first Variac is grounded, you could end up with the second Variac grounded in the middle of the winding. That wouldn't necessarily cause a problem if the load was not grounded, but it would be better to keep the commons together.

If the Variacs are not rated for 600 volts, you could saturate the second one. If that were to happen, it would draw excessive current without a load connected.

Edit 1
As answer 1 says, you can't actually wire the Variacs in series because they are auto-transformers. For a series connection, you need two isolated windings. A variac just has one winding with common primary.secondary connection on one end, a primary tap somewhere towards the other end, and a sliding secondary tap that can be anywhere from the common end to the high end.

The part of answer 3 that suggests 300 V on a 120 V winding is likely to result in a saturated transformer.

Edit 2
Another thing you could try is to connect the Variac backwards. Connect the output to the source. Turning the Variac down would put the source voltage across fewer turns and increase the voltage at the input (now the output). This would be a risky operation. Voltage across fewer turns would be moving towards saturation. If you turned it all the way down, you would be shorting the source.

Answer 2

Although the variac in series might work ......the easiest would be to find a ratio transformer with ratio of 5:1 in that way your output could be withing 3percent and you would still have a usable variac.With a simple 120 volt input. Or lets be creative here a moment lets use the variac like this ,,,power a 120p/240s transformer with the variac. Since the variac is capable of 440 it will do 300 vac no problem... the transformer should be rated for twice the amperage needed and if you power it up with a 1:2 ratio 300 on the 120 side will get you 600 vac on the secondary...Good luck with your project ...be sire and use medium voltage wire thhn,thwn rated 600volts....the ...E

Answer 3

Most variacs are autotransformers. If you connected one in series with another, the output (hot) voltage of the low-side variac would be impressed on the neutral side of the next variac, causing a dead short across the mains, with lots of sparks flying and circuit breakers popping.

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