power supply electronics query

Need some help identifying several power supply capacitors that are
blown, inside a 200V DC power supply. The caps are axial (Poly film?)
and are labeled 103KV 630.
What are these? They are mounted across what appears to be a darlington
power transistor.
ca
Reply to
clay
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I don't know that specific part number but they might be able to help you with that.
Reply to
caveat
103k means 10nF or 0.01uF IIRC the k means +/- 10%
630, maybe 630 voltage rating depending on the topology of your power supply and where they are in the circuit. It could well be 630V seeing it is a 200Vdc supply.
Reply to
Den
These Are 10000PF Capacatiors (103) used as snubbers and depending on what is connected to the Darlington configuration they may be film but my guess would be paper to prevent power up surges that would POP the Collector Emitter junctions since they are rated for 630 Volts in 200 VDC supply. Paper caps would be hard to find these days but you can use a Mylar film type to replace them. If they went more than likely your Darlingtons were cooked. Check the surrounding circuitry there was a reason they cooked. Good Luck.
Cliffybaby
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Verizon News Group Server
Cliffy,
A few more details. I don't think they are Darlingtons. According to a service tech, they are 3 phase bridge rectifiers instead. There is continuity (.4V drop) BOTH directions, tested in-circuit. So that is probably bad news.
The Line voltage measures 250V, the wild leg on the rotary phase converter measures 260V. The machines are rated for 208V, so that is bad too. (working to resolve that) The paper/film caps are rated 630V DC, 250V AC, so that answers one of the failure questions. t The have been running at 250V-260V for five years.
How do you size buck-boost transformers? Load KVA x Voltage drop% = transformer KVA?
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Veriz> These Are 10000PF Capacatiors (103) used as snubbers and depending on
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clay

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