esr of hid lighting caps

[kc8adu]

had a cap on the shops hvac blower die.
its a 10@370.
had degraded to 6uf.
caused hard starting of the blower.
esr of 70mohm.
had a junk hps fixture with a 10@400 about 5 times the physical size.
its esr is .23!
i assume its junk but there is no esr ratings in the datasheets for these caps.
it made things better till the new one gets here monday.
i ASSume the larger can is for lower esr and more surface area to dissapate heat.
anyone have such a cap new and an esr meter?

[stj]

Re: esr of hid lighting caps

larger can usually coincides with higher ripple current.

[delaware74b]

Re: esr of hid lighting caps

Coincidentally, I will be working on 1000-watt pole fixtures tomorrow. The caps used are 24uF 480-volt wet oval cans. If I get a chance, I will try to get esr of a few new ones as well as the duds. The caps I replace have a 3% tolerance. I don't worry about the new ones being higher as much as I worry about the ones being below 23uF. The ones that have low capacitance destroy the new lamps by not allowing them to come out of startup.

[goontron]

Re: esr of hid lighting caps

huh, never even thought of the ESR of these HVAC/Lighting caps. Though in such situations i wouldn't think ESR to be too big of a deal. I mean all they really do is provide phase shift and current limiting.

[Topcat]

Re: esr of hid lighting caps

i've got a new old stock holophane champ series 150w HPS light. I'll see whats in it.

[delaware74b]

Re: esr of hid lighting caps

I brought home 2 caps today from work, a new Aerovox 24uF 480V AC cap and a 1997 bad cap which is also 24uF 480V AC. These caps are used in a 1000Watt metal halide light fixture. The cap is wired in series from the output of the ballast to the center contact of the lampholder.

The caps are oil-filled wet caps with a bleeder resistor across the pins. Tolerance is +/- 3%, leaving a minimum of 23.28uF. Due to DMM calibration differences, we replace anything at or below 23uF. Aerovox publishes expected life at 60,000 hours. The site lighting where these are installed is dated to 1998, so the lighting has an estimated 63k hours at 10 hours per night since 1998.

The ESR rating between the new and bad caps is the same at .07, measured with a freshly calibrated Anatek Blue ESR meter. Personally, I don't think the ESR matters as much as the capacitance in HID fixtures.

The first 2 pics are the new capacitor and the last 2 are the bad cap.