Hi all,
After a half dozen re-writes, I realize I may be asking the impossible, but here goes...
What I need to do is supply 100 ADC to a .001 ohm load and reverse the polarity to this load every four seconds. I'm seeking a (least expensive) solution that can be used in lieu of multiple relays because I believe most contactor relays within my budget would be short-lived.
The most desirable characteristics in order of importance are:
1) Robust design (failure intolerant situation) 2) tolerate 50% duty cycle @ 100 Amps (100% if devices share the same case/heat sink?) 3) operate at as low a voltage as possible 4) Low thermal loss (lowest switching device saturation voltage) 5) easily mounted device(s) to facilitate heat sinking (i.e. TO-220 case style or chassis mountable) 6) easiest and/or most convenient drive requirementsThus far, considerations have included; 4 3PST contactor relays, 2 contactor relays + 2 power sources, 4 SCR's, 2 SCR's + 2 power sources, MOSFET(s), and power transistor(s). IGBT devices were abandoned because I could not find one with low enough saturation voltage, and DC SSR's due to cost.
Optional control scenarios included programming the power source to zero current to turn off SCR's, and in the case of relay's, additionally firing an SCR across the p/s output to circumvent contact arcing (might not be possible if o/p voltage is under 1 VDC?). Obviously, an additional goal is a favorable MTBF of p/s('s) and component choice(s)... .
I have some junk box parts, consisting of used contactors that will support 100 ADC with paralleled contacts (coils are 24VAC, high wattage...), 4 SCR's are on order to at least try (MITSUBISHI TM200DZ-H's X2, but I don't expect these to meet characteristic #4 above), a few SSR's suitable for p/s input or contactor drivers, and several large heat sinks.
Can anyone recommend alternative device(s) (manufacturers & part numbers?!) or even a full switching/control scenario utilizing as much of my on-hand items as practical - that will generate the least amount of excess heat without eating up my two used power supplies that would cost me $4000+ each to replace if I had to do it during a test cycle... .
Thanks in advance!!!! Stephen Kurzban