table saw capacitor

[arborealstudio]

Hi all,

Looking for a bit of advice.

I've an Axminster at315sb table saw which was manufactured in 2019. Saw was purchased second had a few years ago and it's been running fine. Beginning of this year I replaced the capacitor as the saw was struggling to start. This seemed to fix the problem until July when the saw struggled to start again. Replaced the capacitor again and the saw been fine until yesterday when it's now having problems starting again.

I use the saw on a daily basis for work and it's a bit of a pain having the same recurring problem. To keep the saw running I now keep a couple of capacitor in the workshop. The capacitor on the saw is a CBB60 40uf. All other machines in the workshop are fine - just seems to be the saw and I'm wondering if the capacitor is not the problem. Are all capacitors equal - brought the last couple of ebay so just wondering if I should try somewhere else?

Thanks,
Eddie

 

[Sideways]

A couple of points.
It's a big motor according to the manual. 3kW and single phase.
The photos in the manual clearly show a permanent split capacitor setup. That's single capacitor, connected in circuit all the time and no centrifugal switch (hurrah, because those are a famous cause of motor problems).
The caps may just be dying just because they are having a hard working life with such a big motor and proper trade usage. Annoying but not the end of the world.
Make sure you have adequate voltage rating on the caps. Ideally 400v
Capacitors see peak voltages so 240V mains may be 250 coming out of the wall x1.414 to give a peak of 354v.
A decent branded one is likely to be better made and longer lived than an ebay cheapy so consider buying good ones from RS components, Farnell or the like.
Lastly, in a recent thread, I referred to some info from manufacturer Kemet about typical cap sizes for different motors.

https://www.ukworkshop.co.uk/threads/what-capacitor-for-this-motor.149008/

That info makes me wonder if your capacitor is a bit small as Kemet would be suggesting a 60uF cap on a 3hp (not 3kW) motor. Any chance that it could have been undersized at some point in it's life ?

Don't worry about this. A smaller cap will drive the second winding less hard than a larger one so smaller is safer for the motor, but if anyone else has one of these it would be interesting to see a photo of the writing on the side of the capacitor.

HTH

 

[arborealstudio]

Hi HTH,

Thanks for the reply.

Not sure on the history of the saw and if the capacitor been changed or downsized at some point. I just assumed that the capacitor on the saw was the original so replaced with the same spec. Attached is a photo of the original and the saw spec.

Have just sent an email to Axminster to see if they can check the spec for me. Will wait and see what they say before ordering a new capacitor - will go with RS for the replacement to see if it helps.

Thanks,
Eddie

 

[Sideways]

Motor power is what they advertise and your capacitor voltage rating is just fine.

Just swap it out and please do let us know what Axy have to say. Cheers.

 

[arborealstudio]

Motor power is what they advertise and your capacitor voltage rating is just fine.

Just swap it out and please do let us know what Axy have to say. Cheers.

Hi HTH,

Axminster confirmed that the capacitor was the correct spec. Have an RS local to me so will see if a better quality capacitor helps.

They also said that the problem could be from dead spots on the motor. Not sure how I'd test this but will look into further if the saw struggles to start again with the new capacitor.

Thanks again for your help - much appreciated.

Eddie