- Starting cap failure? - 6 Updates
- What can I buy at Walmart for dial string? - 2 Updates
- Radial X2-AC Safety Capacitors (Question) - 2 Updates
| etpm@whidbey.com: Aug 24 03:31PM -0700 I run my machine shop off af a rotary phase converter. It has starting caps that are switched out of circuit after the motor is started. Lately the device sometimes has a hard time starting. I switch it on and the motor may not come up to speed practically instantly, the way it is supposed to. If this happens I turn off the breaker, wait a minute, and then try again. It always starts fine on the second attempt. Except this morning it took three tries for the thing to start. The motor did actually spin up some this morning on the first try but it was really slow starting so I shut the breaker off. I suspect starting caps but wonder why the second attempt always worked until today. And then today it started fine on the third attempt. The phase converter has been started almost daily for at least fifteen years using the same breaker in the main breaker panel. I thought that maybe the breaker might be making a bad contact on one leg of the single phase 250 volt input. Or maybe a contactor inside the converter is not making good contact. Or maybe, and I think most likely, the starting cap(s) is(are) the problem. I just wonder why, if the thing doesn't start spinning right away on the first try it does on the second or third. This weekend I'll have time to look inside the phase converter and I would like to know if there is a way to diagnose the starting caps. The contactor contacts I know how to check. And I could buy a new breaker. But I would like to not just buy stuff until the thing works properly. Advice? Thanks, Eric |
| Ralph Mowery <rmowery28146@earthlink.net>: Aug 24 07:32PM -0400 In article <5ujupclqvbqv63fcgrqa0smbbib74g9p5k@4ax.com>, etpm@whidbey.com says... > Advice? > Thanks, > Eric There are many ways to check the capacitors. You can find capacitor "meters" and testers from about $ 15 up. You may be able to find a shop that works on air conditioners and take the capacitors to them and have them checked. Usually they will have a voltmeter device that just hooks across the capacitor. Takes longer to find the meter than to check the capacitor. |
| Rheilly Phoull <rheilly@bigslong.com>: Aug 25 09:25AM +0800 > Advice? > Thanks, > Eric After 15 years I reckon I would just get another cap and see if that fixed it. What sort of device takes out the cap, centifugal ? |
| tabbypurr@gmail.com: Aug 25 12:50AM -0700 On Friday, 25 August 2017 02:25:46 UTC+1, Rheilly Phoull wrote: > > Eric > After 15 years I reckon I would just get another cap and see if that > fixed it. What sort of device takes out the cap, centifugal ? Or as a quick test clip some additional C across it. NT |
| Phil Allison <pallison49@gmail.com>: Aug 25 01:13AM -0700 tabb...@gmail.com wrote: ----------------------------- > Or as a quick test clip some additional C across it. ** That reminds me of what was the common practice with suspect electros BEFORE we all got ESR meters. How quick we do forget. .... Phil |
| etpm@whidbey.com: Aug 25 09:26AM -0700 On Fri, 25 Aug 2017 09:25:37 +0800, Rheilly Phoull >> Eric >After 15 years I reckon I would just get another cap and see if that >fixed it. What sort of device takes out the cap, centifugal ? There is an electronic device that's got its innards potted. It senses the starting current and when the current drops to the set level it drops out the contactor that connects the starting caps. There 10 starting caps connected in parallel so I don't think it's such a good idea to replace them all just in case that's the problem. They are all stuck in place with some pretty good double sided foam tape so removing them would be a hassle too. I cannot see how many mfd the caps are rated for but I can see on one cap that they are made for a phase converter. I just remembered that years ago the device mentioned above failed. When I tried to start the converter it would just hum. There is a button inside that I can press that bypasses the starting device and energizes the contactor coil. When the starting device failed the first time I was told by the phase converter maker to press this button and see if it starts OK. It did which is how I diagnosed the problem. The company that made the converter has gone out of business so I can't call them for advice. But I'm gonna try the button thing again and if it starts fine then I guess I know the problem. What I don't understand is why the converter sometimes starts to spin up slowly and at other times just sits there and hums loudly. And then starts just fine on the next attempt. Could it be that when it starts to spin up slowly that the rotor was in just the right position that the balancing caps in the converter provide enough phase shift to start spinning the rotor, albiet slowly? Thanks, Eric |
| Tim R <timothy42b@aol.com>: Aug 25 06:51AM -0700 If all else fails go to a music store. The valve linkage on French horns and some models of trombone are strung with the same stuff. (of course most of us use fish line) (but you can buy the stuff designated for instruments) |
| John-Del <ohger1s@gmail.com>: Aug 25 07:08AM -0700 On Thursday, August 24, 2017 at 4:18:33 PM UTC-4, Trevor Wilson wrote: > -- > Trevor Wilson > www.rageaudio.com.au Free is a admittedly a generous offer Trevor, but can you do better? |
| Dimitrij Klingbeil <nospam@no-address.com>: Aug 25 12:45AM +0200 >> is like wearing a belt and suspenders. > You need belt & suspenders since both fail. Just don't put the pics > online. :) Besides, using an X2 capacitor does call for an additional means of protection. Capacitors rated for being connected across the line "X" come in different sub-categories: "X1" and "X2". "X1" capacitors are rated for a 4 kV transient overvoltage and they are often found where no other means of protection (fuse) is installed in the equipment "upstream" of the capacitor (that is directly across the power line). "X2" capacitors are only rated for a 2.5 kV transient overvoltage and the circuits they are installed in need to be fused as an additional means of protection (additional besides the dielectric in the cap). Both X1 (rated to 4 kV pulse) and X2 (rated to 2.5 kV pulse), when used within their specifications and unless their safety certifications are fake, tend to be better protected than "plain" 600 V type capacitors. The voltage ratings indicate the maximum AC line voltage that the X or Y capacitors may safely be connected to (not their peak pulse ratings). So, it's correct (and would be required in a repair) to replace the old 600 V capacitor with a 250 V safety rated "X" capacitor (assuming the nominal mains voltage in your country is not higher than 250 V), but if the capacitor is an "X2" (rather than "X1") type, the device also needs to be fused "upstream" (on the mains side) of the X capacitor. Regards Dimitrij |
| Phil Allison <pallison49@gmail.com>: Aug 24 05:11PM -0700 olds...@tubes.com wrote: ---------------------------- > .047 at 600V (standard capacitor). I was told that these days, standard > caps are no longer used across the AC power line. Instead, they use > these Radial X2-AC Safety Capacitors. ** The use of 600V DC rated caps across a 120VAC supply line is time honoured and normally perfectly OK - long as you are not in a high lightning area. The issue that arose was in 240VA counties when wax impregnated paper caps were replaced with plastic film types. Some of these would last only weeks before developing internal shorts and exploding. The problem was soon found to be due to tiny pockets of air trapped inside the cap when being wound - corona discharge developed across these pockets and destroyed the cap. However, such corona currents did not normally occur with 120VAC so US makers kept using plastic film types. The fix for 240VAC places was to use two 600V film caps is series, thereby limiting the effective voltage to 120VA for each. Cap makers in the UK and elsewhere developed a method of winding "two in series" film caps as a single part and these became standard for class X caps. .... Phil |
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