Starting Capacitor for a Motor

[Mike Henderson]

I don't do a lot of turning, but yesterday I was using my lathe and when my wife walked up to me, I turned it off. After we finished talking, I tried to turn the lathe on again and it was dead.

Since starting capacitors are the usual cause of a motor failing to start (maybe 90%), I immediately went online looking for a replacement. I could find the proper size in microfarads but could not find one that was physically the same size – they were all larger.

So, I bought one that looked good and had screw terminals.

I received it today, hooked it up and everything worked. My next problem was how to mount it safely since it wouldn’t fit into the cover that fit the old one. I used some shrink tubing, electrician’s tape and zip ties.

I had this same problem with the motor on my dust collector and had to tie the new capacitor to the motor with zip ties.

It’s a shame you can’t find capacitors of the same physical size.

In the pictures, the old capacitor is sitting on top of the new capacitor.

Mike

IMG_2572.jpg IMG_2573.jpg

[Cary Falk]

This is one of the reasons I love having a 3D printer. I would be happy to print you a cover that you could probably screw into the original screw holes for the cost of shipping. PM me if you are interested.

[Mike Henderson]

This is one of the reasons I love having a 3D printer. I would be happy to print you a cover that you could probably screw into the original screw holes for the cost of shipping. PM me if you are interested.

Thanks for the offer, Cary. Because the new cap is longer, I'd have to drill a new hole on the back end. I'm a bit hesitant to do that because I might hit the field coil.
I’m happy with what I have – it’s safe but not pretty.

Mike

[Aaron Inami]

Can you check to see if your old/bad capacitor was an electrolytic? Sometimes they will use an electrolytic for start caps and these are definitely smaller, but can burn out a lot faster when used as a "motor start" capacitor.

That being said, I don't see any problem with how you jerry-rigged your new cap. As long as the cap is secured well and has good electrical connections, you should be fine. I see you even did some tape-over on the exposed contacts.

There are a couple from Mouser that are 36mm x 70mm (1-7/16" x 2-3/4"):

https://www.mouser.com/c/passive-com...%20Rating%20AC

[Mike Henderson]

Thanks for the info. The old capacitor is 34mm in diameter (about 1 5/16) and 58mm long (excluding the terminals, about 66mm with the terminals)(about 2 5/16 long, or 2 11/16 with terminals).

I'll look at the link you posted.

Mike

[Update: I went ahead and ordered one. It's on backorder. Hopefully, it will fit into the cover. I didn't know about Mouser before.]

[Bill Dufour]

Folks who make RPC's put al lthe caps in a metal box somewhere and run wires to the motor. No reason the wires can't be several feet long. My old Stanley grinder the capacitor is flat and sits inside the base. No way will I find a replacement. I believe they stopped making that model in 1938.
Bill D

[Patty Hann]

.... I didn't know about Mouser before.]

Mouser is super great for electronic/electrical parts.
You can buy small quantities and the pricing is competitive
I first came across Mouser when I worked in Aerospace. They carry Mil-Spec and non Mil-Spec parts.
Shipping costs are reasonable.
I still continue to use them 8+ years after I left Aerospace in the rearview mirror.

[Ken Fitzgerald]

Over the years I have bought a lot of parts from Mouser.

[Brian Deakin]

I replaced the capacitors on my bandsaw and used Wago connectors I think these are an excellent solution for connecting wires
There are a number of videos on Youtube Below are 2 example

https://www.youtube.com/watch?v=wb9K...nnel=HowToHome

https://www.youtube.com/watch?v=5-Yc...=WAGOSingapore

further there are a number of varients

[Mike Henderson]

I replaced the capacitors on my bandsaw and used Wago connectors I think these are an excellent solution for connecting wires
There are a number of videos on Youtube Below are 2 example

https://www.youtube.com/watch?v=wb9K...nnel=HowToHome

https://www.youtube.com/watch?v=5-Yc...=WAGOSingapore

further there are a number of varients

Those look fairly large for tight areas. But they are very easy to use. How about these? They're a little bit more work but look like they might fit in small spaces better.

And then, I might just solder the wire together and use shrink tubing to cover the splice.

Mike

[Bert McMahan]

Mouser is super great for electronic/electrical parts.
You can buy small quantities and the pricing is competitive
I first came across Mouser when I worked in Aerospace. They carry Mil-Spec and non Mil-Spec parts.
Shipping costs are reasonable.
I still continue to use them 8+ years after I left Aerospace in the rearview mirror.

Digikey is another great resource. I find Digikey's search easier to use than Mouser's but they're both quite good. Sometimes one place will have stock in parts that the other doesn't.

[Aaron Inami]

I have found that Digikey really doesn't specifically stock "motor start capacitors". That's why I referred the OP to Mouser.

[Patty Hann]

Digikey is another great resource. I find Digikey's search easier to use than Mouser's but they're both quite good. Sometimes one place will have stock in parts that the other doesn't.

I've used Digikey, Allied and Newark as well as Mouser.
In order of preference (balancing price and parts stock):
Mouser
Allied
Digikey
Newark

[Mike Henderson]

I found a capacitor on Amazon that is 36mm by 70mm, just a bit larger than the old capacitor. I received it today.
IMG_2598.jpg

It did not come with screw terminals so I drilled the tabs and threaded them for the M3 0.5 screws and took the screws from the original cap.
IMG_2599.jpg

Although a bit larger than the original, I was able to put it under the cover.
IMG_2600.jpg

So, now my lathe looks like it always did. I don't know what the quality of the cap is - China made - but if it fails, I have the physically larger cap that I can replace it with.

Mike

[Oh, I'm trying to cancel my order at Mouser. The cap they had is on backorder so I should be able to cancel it.]

[Bill Dufour]

Wago makes some smaller connectors that are single wire at each end, inline. Similar to those butt splice connectors but easy to connect and disconnect. They only came out this year, so not too many know about them. AFAIK most Wagos max out at #10AWG size. Most only go to #12 AWG. Copies are sold made in China. I believe Wago is only made in Switzerland and their prices reflect that.
Bill D.
https://www.wago.com/us/wire-splicin...ver/p/221-2401