Coil Power Supply

13 02 2010

Joe Khachan just sent me details on the power supply for the coils. They are designed to produce a brief high current pulse.

Joe says:

The part that took the most time to build was the power supply. I’ve attached a diagram that looks something like our circuit without dump resistor to dump charge of the capacitors when we need to service them. We used a hockey puck type of SCR (a type of thyristor) that can take 1000 A continuous or 10 kA pulsed. This may have been an overkill because we found that a maximum of 300 A was needed. However, we may need higher current as we increase the size of the polywell. The capacitor bank was make of 5 X 1500 microFarads electrolytic capacitors that can take a maximum of 450V all connected in parallel. You need some kind of transformer that can step up the voltage from the mains and be able to charge the capacitors within a couple of seconds. That means it shoud be a reasonably hefty transformer. We control the voltage output of the transformer with a Variac on the input side. You need to protect the SCR from back EMF with a diode across it. The diode should be able to take a few amps. The wire diameter about one millimeter and there were 10 turns per former.

Joe’s coil power supply looks like this:

Here is the preliminary bill of material (click for Mouser produce page):

1500 microFarads electrolytic capacitors max 450V

Silicon-controlled rectifier (SCR)

Diode Diode to protect the SCR from back EMF

Step-up Transformer Step-up Transformer

Variac

Power Rectifier

Trigger Isolation Transformer

18 AWG magnet wire

100 watt 2KΩ resistor for bleeding capacitor bank

Rack mountable chassis.

Please comment if you notice wrong parts.

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