In this application I do not see the need for such an extremely high power supply capacitance. Especially so given that in common commercial high current power supplies they only have a hundred to a few hundred uf per running amp at most on a 60 HZ iron core transformer based power supply.
In my books for a ~150 amp 22 VDC power supply 30 - 50,000 uf of lower ESR electrolytics backed by a few hundred uF of poly capacitors or even old metal can PFC capacitors to compensate for the HF load aspects would be a great plenty.
Hi TCM,
Do you know, I have been wondering how such relatively small capacitors were used in the power supply of Garry's previous induction heaters, and now you say that commercial induction heaters also use relatively small capacitors. Taking your example, and inserting a 100uF per running amp gives, 150A * 100uF = 15,000uF total, This is a much more manageable value of capacitance, as you imply.
Such low value capacitors would result in the plus and minus 22V lines being, to a first approximation, 120Hz rectified sine waves, rather than DC with a 1V ripple at 120Hz, as I had intended.
While a power supply with such a high ripple would be anathema for other applications, say a high power audio amplifier, I can see that it would be OK for an induction heating coil application.
The high ripple power supply would only produce * 0.707 of the heating effect in the coil of the low ripple power supply, and the capacitors would need to stand the very high ripple voltage (and thus ripple current), but the advantage of much lower value capacitors far outweighs the disadvantages. And the rectifiers and transformer would have a much easier time.
spec
PS: I bet with a high ripple power supply the induction heating coil makes an ominous noise under full steam- like a Frankenstein machine.
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