Question about failing starter capacitors on electric motors

Thanks for the feedback... I like to know what people building the kits are experiencing, so I know what they're talking about if they contact me about problems.

Bob

Oh, and your software fault diagnostics works a treat too. Built mine in haste during lunch hour at work and my brain wasn't switched on, so accidentally installed a wrong value resistor and got the F1 error message :-/ Yes, you can build it and test it (and troubleshoot it) in under 1 hour, and still have time to each your lunch.

Dave :)

I did the self-test function to try and reduce the number of e-mails I was getting from people with construction problems (mostly solder whiskers). It was amazingly successful.... I hardly get any e-mails like that now. :)

Bob

oh yeah. I've got a bus discharge resistor I made up in the 90's when I was a design engineer at PDL electronics, designing motor controllers. Its a pair of 50R resistors in series, each rated for 11kW peak pulse power, coated in heatshrink and attached to a pair of fluke DMM leads. the tips are a lot shorter now than when I started ;)

We used these in our production test area to discharge the DC bus of drives that had been tested. a 400V 660A drive had 19.8mF at 800V (after regeneration) so about 6.4kJ peak; from the AC line it was a mere 560V, so only 3.1kJ. The 1MW drives were three 660As in parallel, so almost

occassionally the test tech would forget to turn the drive off before discharging the bus. big problem, as you cant remove the leads, it just arcs, shorts the DC bus and BANG goes $50,000 worth of product. And if you left it there, the resistor went bang (and it typically pointed at ones groin). So they'd scream, and someone would hit an E-stop and knock out all the test bay power.

Fun stuff. One learns to be VERY careful.

Cheers Terry

eeek! Better you than me!! :)

Bob

they scared the shit out of me during my interview. I'd never seen 2" thick wires before, let alone ones that jumped about, and made watches spin crazily. rubber mats and one hand in the pocket was de rigeur, nad nobody worked alone. But their most serious accident was an office lady falling off a mezzanine floor, and braining herself on the concrete floor.

although one night the fire alarm went off, so me and a couple of other engineers went to investigate (naughty us). a 600A test machine had poled, and flames were pouring out of it. we hit an E-stop, and it didnt work. So we pulled a trip cord, and that didnt work either. I ended up leaning over the drive, scrolling down to the start/stop screen and telling the drive to stop.

Turned out that morning marketing had been taking photos in the test area, and made the guys take the trip cords down. but they were fail-safe, so someone had jumpered them with clip leads. which conveniently disabled all the E-stop buttons too. Only problem was they forgot to remove the clip leads.....

Cheers Terry