Selecting a Start & Run Capacitor for a 2850rpm mains induction motor

[GreensandsParticipant @greensands]

Hi – I have attached a photo of my vintage 2850rpm GEC induction motor under test with an equally vintage TCC capacitor wired into the circuit using a micro-switch to attain a push On/Off capacitor start arrangement. The capacitor is one that I have had in my collection and is rated 40-50mF at 275V and everything is working as expected with the motor without any signs of running hot.
What I would like to be able to do is to change to a capacitor Start and Run arrangement using a modern choice of capacitor physically smaller in size compared to the one shown which measures 6”x1.5″ Diameter.
Can anyone suggest a possible source of Start and Run capacitors which might be suitable for the above arrangement.

Finally, what actually defines a Start and Run Capacitor as opposed to a Start Capacitor and how can you distinguish one from another?

[Greensands]

On 19 February 2025 at 12:13 Greensands Said:

[…] Finally, what actually defines a Start and Run Capacitor as opposed to a Start Capacitor and how can you distinguish one from another?

 

Can’t say for sure … but others will no doubt be confident

What I can say, however, is that the ebay seller I used recently [for the one on my Document Shredder] was excellent.

MichaelG.

.

https://www.ebay.co.uk/str/workshopnr1

[Robert Atkinson 2Participant @robertatkinson2]

A run capacitor has to pass current all the time the motor is running so they generally have thicker electrodes making them bigger and more expensive. A “run” capacitor can be used for starting assuming the value is correct. Hence the they are often called start/run.
Is the motor marked with a capacitor value?

Robert.

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