Hi,

I am new to this forum. I am a student and don't know much about electrical engineering.
I have a commercial vent fan from 1916 I am trying to restore to functioning condition. It had what I assume was a run capacitor from Singer (yes, the sewing machine company) rated for 500v and 4.3µf. I cannot find ANYTHING in that size and don't know what to replace it with. I think it's important to mention that I used some alligator clamps and got this thing fired up without the cap just to see if it functioned and it was pristine, although slow to get started obviously.

Any help would be appreciated.

Thanks!

Moe

 

You need to obtain a motor run rate capacitor, there are a few N.A. manuf. (do not use Chinese origin)!
I believe Mouser sell versions made by CDE.
BTW that looks like 4.7μf ?

https://www.mouser.ca/ProductDetail/Cornell-Dubilier-CDE/32FD3705A-F?qs=rVFmcZtbgVgxvqZIXwhWEg==

.

 

Such capacitors are commonly available from electrical suppliers, appliance repair shops, or online as above. They are often 450V rather than 500V which I think is ok to use.

 

The CDE I recommended are generally 370VAC, which are fine.

 

You need to obtain a motor run rate capacitor, there are a few N.A. manuf. (do not use Chinese origin)!
I believe Mouser sell versions made by CDE.
BTW that looks like 4.7μf ?

https://www.mouser.ca/ProductDetail/Cornell-Dubilier-CDE/32FD3705A-F?qs=rVFmcZtbgVgxvqZIXwhWEg==

.

So it's definitely 4.3µf, but it begs the question for me, is a 370v, 5µf going to be ok for that motor? I don't know enough to understand what over or under voltage may do and what the tolerance is for a variance in µf.

 

Usually no problem, the 370v rating should be fine, and capacitor values of that type are ±10% anyway.

 

the motor start capacitors have poor tolerance and vintage your original capacitor it was way worse.
btw. if transients, line and load fluctuation are concern, you could simply use 2 capacitors that are double the capacitance and connect them in series. series connection halves the capacitance but increases voltage rating.
so two 8.5 or 9 uF 370V caps will be a good substitute and this will be good for 700V.

 

The CDE ones I referenced I have used for years and they are specifically made for motor start/run. IOW in circuit the whole time the motor is powered.
120VAC & 240VAC motors.