Mini lathe 50 odd years old, the motor not original. I would like to reduce the size of the electric box. It contains an on off switch, an indicator lamp, and a reverse switch. Inside is a large capacitor which takes up the space if I can replace the capacitor with a smaller dimension then I can reduce the elec box size. Is a more modern one smaller and if so what sort of ratings am I looking for on eBay?
Image:
image not visible. It'll be a motor start or run cap, look those up of the capacity yours is (in uF). Pick the same uFs & voltage rating.
NT
Try this link.
4uF 440V AC
Thanks Alan that would be ideal thats about quarter the size of the one thats currently installed.
It looks like a 4 uF motor run cap.
Something like:
Why is a 440v AC capacitor being used with a 230/250V motor?The OP did say the motor had been replaced, so maybe it was a 440V (3 phase?) motor previously, although that seems a bit strange for a mini-lathe. Anyway, that capacitor is well past its sell-by date if the "1966" on it is accurate. I haven't checked, but a 240V capacitor should be even smaller.
It wasn't visible with Pale Moon, but was with FF 80.0. I'd seen this before with Imgur and PM a week or so ago, so something on Imgur doesn't like Pale Moon, or vice-versa. Unfortunately the PM forum server seems down at the moment, so I can't check if it's been reported previously.
jeff Layman has brought this to us :
240v RMS, the voltage peaks are much higher and the cap needs to be ac rated.A three phase motor would not have needed a start/run capacitor. Likely, one single phase motor has been replaced by another. Perhaps the original was an ac/dc type motor.
er. Does the 440V represent the peak voltage encountered? 3 phase would not require a capacitor.
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Fails 404. He is right though it is a run capacitor and you will need one that is about the same value and voltage rating. It may not be all that much smaller unless your lathe is truly very ancient.
Rapidonline will give you some idea of typical dimensions for mains:
The capacitor has to survive being attached to 240 rms ac mains voltage which has peaks 1.4x higher and with a margin for the odd glitch.
This site labours the point a bit but shows the difference.
What if the cap is charged up one cycle and power is applied with the other cycle. That wound mean you need a 750V cap
It is an Emco Unimat SL1 . Originally it would have been fitted with a universal (AC/DC) motor identical to the ones fitted to Singer sewing machines so no capacitors needed and easy reversing.
There are quite a few videos and other posts around on fitting assorted motors to these lathes. The original universal motors were somewhat underpowered and ran hot so failure was common and all sorts of replacements were used. The induction motor fitted to yours would have required modification to the original very simple wiring to allow it to reverse.
Completely blank for me I am afraid. On desktop firefox
Mobile sees it by as I tried to zoom in it vanished to be replaced by pictures of dogs and cats.
The brief glance I got suggests it is a typical 'phase lead' starter cap of the oil and paper variety that could easily be substituted by something one tenth the size if you had actually said what value it was...
Error 404
A 400VDC cap is what is needed on 230V AC, but not '440VAC' which is more like 630vDC from memory
not really,no. Its not in a voltage doubler.
It would be. I didn't bother stating "AC" again for the 240V capacitor as I had made clear the original was 440V AC.
Were there many 440V single-phase motors around in 1966? It just seemed an unusual combination for a fairly low-power device.
It doesn't quite work that way. A capacitor put across a voltage instantaneously looks like a dead short until it starts to charge.
A charged capacitor the wrong way around could double the inrush
*current* but it wouldn't take it out of operating voltage range.Have something to add? Share your thoughts — no account required.
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