help needed to find capacitor for old British Thomson Houston motor

[Pete the Feet]

hi, this is my first post though have been reading threads on here for a while. It seems somebody always knows the answer and if they don't they can point in the right direction. I'm hoping someone can help me here. I have an old British Thomson Houston motor which I want to use on a small lathe as it is 1425rpm. The old capacitor wiring was completely corroded and I need to replace the whole thing. There is no spec on the old capacitor casing to allow me to identify it nor is there the required information on the motor spec plate (see below) to use an online capacitor calculator. These invariably ask for motor power in watts, motor efficiency (in %), and frequency in Hz. I read on another forum that someone had replaced the capacitor on a similar motor but that was eight years ago for a start and they didn't give any details. I don't want to scrap it if I don't have to and second hand ones are expensive or too far away for collection, I'm in DT11. I'm grateful for any help. cheers Pete

 

[TheUnicorn]

hi, this is my first post though have been reading threads on here for a while. It seems somebody always knows the answer and if they don't they can point in the right direction. I'm hoping someone can help me here. I have an old British Thomson Houston motor which I want to use on a small lathe as it is 1425rpm. The old capacitor wiring was completely corroded and I need to replace the whole thing. There is no spec on the old capacitor casing to allow me to identify it nor is there the required information on the motor spec plate (see below) to use an online capacitor calculator. These invariably ask for motor power in watts, motor efficiency (in %), and frequency in Hz. I read on another forum that someone had replaced the capacitor on a similar motor but that was eight years ago for a start and they didn't give any details. I don't want to scrap it if I don't have to and second hand ones are expensive or too far away for collection, I'm in DT11. I'm grateful for any help. cheers Pete
View attachment 103980

pete it might be worth a call or email to miles tools in yeovil, Miles Tool & Machinery Centre

 

[TheUnicorn]

this thread might help Motor start capacitor - value ?

 

[Droogs]

@Myfordman may be able to help on this

 

[Myfordman]

Did someone call?
Rule of thumb for these older motors on UK voltage/frequency is around 20mfd per horse power so in this case 5mfd should be about right and 4 to 6 would work. working voltage should be 400-450 no lower. Several reliable suppliers on ebay. Note they come with tags or short cables moulded in which can be convenient. Some have mounting studs (electrically isolated) and some have both.
https://www.ebay.co.uk/sch/i.html?_...tleDesc=0&_osacat=0&_odkw=motor+run+capacitor

 

[Pete the Feet]

Thanks everyone who has replied I really appreciate it. I've tried replying individually but an error message accuses me of spamming my own message . I'll update when I have looked into some options. Thanks again.

 

[Cabinetman]

Our resident experts have come to the rescue again. You won’t be able to send personal messages until you have a few more posts on here, it’s not a huge number but I can’t remember what it is sorry. Ian

 

[TheUnicorn]

thinks its 3 messages that's needed. should be good now?

 

[Pete the Feet]

I'm sure I'll get the hang of it! Let's see if this works, Thanks for the info.

 

[minilathe22]

Might be worth checking the motor works ok, before adding the capacitor. without a starting cap it should fire up if you firmly flick the spindle with it connected to power.

 

[Pete the Feet]

Might be worth checking the motor works ok, before adding the capacitor. without a starting cap it should fire up if you firmly flick the spindle with it connected to power.

Thanks for the tip and I will give that a try

 

[Pete the Feet]

Did someone call?
Rule of thumb for these older motors on UK voltage/frequency is around 20mfd per horse power so in this case 5mfd should be about right and 4 to 6 would work. working voltage should be 400-450 no lower. Several reliable suppliers on ebay. Note they come with tags or short cables moulded in which can be convenient. Some have mounting studs (electrically isolated) and some have both.
https://www.ebay.co.uk/sch/i.html?_...tleDesc=0&_osacat=0&_odkw=motor+run+capacitor

hi, thanks for your help and also for the link to the induction motor file. A very good read. It's nice to read something in terms that I can follow