ac oil cooled to dc rectifier built 200 amp

[shenion]

The capacitor value is only to absorb spikes. Normally there is 0.5uf across each diode to eliminate spikes and also RF interference.

No if you wanted to add enough capacitance to get smooth DC, you would need a lot and 50/60hz would make a difference on size.

I think I calculated it would need about 100,000uF for 100A at 60 Hz to get about 25% ripple. That would be 120,000uf at 50Hz.

A MOV would help more than caps as it will clamp spikes and still allow the reactance to provide smoothing of the arc. If you add a lot of caps the arc will become harsh as the reactor is on the far side of the bridge.

A voltage spike will cause the diodes to avalanche and then the become a dead short until current goes to 0.

I'd look for some 200A or better diodes or diode modules (2-diode bricks.) THey can be had fairly cheap off ebay. Here is a set of 10 that you could parallel the diodes for 300A. Would still need protection.

 

[lovelectricity]

ok we'll go down that route. looks like better way, gotta get the end fed antenna up first though. strip out the ammo box, it aint gonna be big enough for those, oh find a new heat sink, rewire. great got a new but the same project on the go. I LOVE IT WHEN A PLAN COMES TOGETHER. erm if the two diodes are wired in parralell then the units used to make a bridge, will the current go for the weakest diode?

 

[shenion]

Since the diodes are out of the same lot, they should be matched. They also are on the same heat sink, so their current/temperature slope will match also.

 

[Robotstar5]

gotta get the end fed antenna up first though.

What are you doing?, inverted "L" for 40, 80 or have you got enough room for top band?

Stuart M0BTO

 

[seb21051]

Lamp Load regulators

I have been contemplating building a 5 x 50 Amp Bridge rectifier similar to yours.

I also had the idea to use it for the odd plating job, especially Hard Chrome, which requires a lot of current.

Anyway, from the Plating side I saw a technique for controlling the current using incandescent lamps. It occurred to me to put automotive halogen lamps in the positive line of each rectifier, although the voltage spike might kill them; anyway, they handle 50/65 amps, and could be seen as limiting resistors, to help combat current runaway. It is standard in circuits like these to use low resistance high wattage resistors to provide for balancing the individual rectifier's loading and current limiting.

Another thought is to use 6 to ten rectifiers, that way each would be contributing less, and therefore less stressed. I found these guys, and at a price of $4.00 for a 1000V 50 amp bridge one could possibly afford to splurge:

http://www.virtualvillage.com/50a-1000v-gbpc5010-bridge-rectifiers-007901-001.html

I estimate that a 12 x 12 x 3/8 inch AL plate for each pair should work, if forced air is blown over them, and it could be mounted in an open frame box.

Anyway, glad to have found like minded thinkers!