ant1dp
Active Member
Loving building parts for my superbike
Posts: 17
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Post by ant1dp on Apr 13, 2024 19:52:52 GMT
Thanks for your indepth explination of 3 phase but ill just trust you that they are better and with Elders £128 converter they look like an option.
I assumed one capacitor was for each direction because it still runs in reverse for the mill.
Safety - What precautions should I use when taking the old ones off and plugging new ones in? obviously mains off but one time I was playing with a photo flash gun and gave myself a right whollop! and the batteries had been out for a while, so im thinking capacitors could kill me.
Thanks
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SteveW
Elder Statesman
Posts: 1,398
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Post by SteveW on Apr 13, 2024 21:05:53 GMT
Ant1DP.
As Andy added, its likely that one capacitor is your motor starter, the other is your motor keeper going-er capacitor. The starter capacitor usually gets switched out of circuit by a rotor speed switch once spinning, its the click when it all stops again getting it ready to start again.
As outlined earlier the capacitors help generate the rotating magnetic field inside the motor. The direction of the field's rotation is determined by the way the one or more coils are connected via the magic of the forward/reverse/On/Off switch.
Maybe if your motor will only rotate in one direction you should look to a broken wire/connection/switch and NOT the capacitors.
If you are worried about getting a belt from the capacitors unplug the system, wedge a screwdriver or similar across the plug's live and neutral pins and cycle the forward/reverse/On/Off switch a couple of times. Also be a little suspicious with the capacitors even when not connected. Best keep their terminal wiring connected together to dissipate any residual charge that might magically build up and surprise you later.
If you are really worried about getting a shock best roll both your sleeves up and then get both hands as deep in your pockets as possible before you start fiddling.
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ant1dp
Active Member
Loving building parts for my superbike
Posts: 17
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Post by ant1dp on Apr 14, 2024 21:03:22 GMT
Thanks for your safety tips Steve, ill certainly try shorting them with a screwdriver and ill wear rubber gloves.
Well the 20uf cap turned up but the 75uf is coming from china. Ive searched everywhere and I cant find a 75uf in the UK but I have found 70's and 80's. Do you think it would matter if the capacitor was 5uf's higher or lower?
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SteveW
Elder Statesman
Posts: 1,398
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Post by SteveW on Apr 14, 2024 23:42:53 GMT
Thanks for your safety tips Steve, ill certainly try shorting them with a screwdriver and ill wear rubber gloves. Well the 20uf cap turned up but the 75uf is coming from china. Ive searched everywhere and I cant find a 75uf in the UK but I have found 70's and 80's. Do you think it would matter if the capacitor was 5uf's higher or lower? In absolute terms my answer has to be "IDFK". Bottom line being if the label says use "75uF" and "25uF" capacitors its likely the fella that designed the motor wanted folk to use those values. You don't drill a half inch hole and expect to get a three quarter inch shaft in there. Chances are that abusing the stated capacitor values will still get your motor turning but maybe not as efficiently as before. It might have reduced power or run a lot hotter which in turn may not end well. All that said, (written), factoring in the fact these run/start capacitors could be off value by a much as 20% there are chances to be taken. However, better to be within 20% of the stated value. If your current capacitors show no signs of leakage or other damage maybe there's nothing wrong with them and you actually have a wiring fault in there somewhere. Certainly the odds of both capacitors going is relatively low but once suspected certainly be ready to change them. Edit: there are 70uF and 80uF capacitors here as well as 50uF and 25uF which paralleled gets you your 75uF value. Seems that link doesn't work for me so cut n'past this (but without the quotes ".."): "https://cpc.farnell.com/c/electronic-electrical-components/capacitors/film-capacitors/motor-run-motor-start-capacitors/prl/results/2?st=run%2Fstart%2Bcapacitors"
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weary
Part of the e-furniture
Posts: 290
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Post by weary on Apr 15, 2024 7:47:35 GMT
Hello OP, Quite a few 450v 75uf capacitors located UK, delivery 2/3 days on ebay (2nd class mail transit times). Item no: 143605111682 (located NI) will give you suitable search terms. (Restrict your 'item location' to UK only'.) I note that the same vendor also supplies 25uf. Maybe also search +++ 450v Motor Capacitor ++++ & similar broad-brush terms (on ebay) as well to give you general stockists & also don't forget to check if suitable supplier has a non-ebay webpage for better pricing. As an aside, the 'item description' explains that 'start capacitor = 250v & run capacitor = 450v'. But suggest that you replace both with 450v. Oh; and the item description gives the dimensions so you can check that the item will fit if space is tight! Regards, Phil
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ant1dp
Active Member
Loving building parts for my superbike
Posts: 17
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Post by ant1dp on Apr 15, 2024 19:43:39 GMT
Hi Weary - Thanks for finding that but £20, im getting 2 from china for £12 so ill try and be patient.
Guys im starting a new thread about updating my turntable, its Batman level project and id really enjoy your input.
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