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Info on Coronot Major lathes

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Samara

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I have an issue with my Coronet Major and need some info to help me solve the problem. The motors capacitor has packed up. I am unable to find a value to indicate the size of the failed capacitor o it or anywhere else. Would anybody known the size or type of replacement needed please? The motor is 1 hp single phase PROT type (not sure what means), 230 - 240 v, 2850 RPM. Hope this info helps.
 

Simon_M

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2850 rpm is an indication that it's a 2 pole (induction) motor especially as it's single phase. *** edited # of poles ***.

For a 1 HP motor (0.75kW) the range of start capacitor is between 140 uF to 180 uF. The value is usually printed on the capacitor or it may be specified on a motor housing plate. That's more logical because if it's replaced, the plate never changes so a replacement is not difficult to identify.

The type of capacitor is important because you can't use an electrolytic capacitor (cheap and high capacity) so it's usual to use a polyester type capacitor (can be quite big and generally more expensive).

The size of a capacitor increases with voltage (and capacitance) so they can be quite big. The rating for a motor capacitor must be at least 250 VAC and it's more usual to specify 450 VAC (to be sure there won't be problems).

There are plenty of starter capacitors on Amazon - they will specify XX uF at 450 VAC and also the size and form factor. e.g. if yours has terminals you want one like this or if it has leads that you connect then this will be the type. From the size you can also work out it's approximate capacity. One way they specify the values is 450/150 uF.

A starter capacitor is used with a winding that is connected to a centrifugal switch - when the motor gets to about 70% of it's full speed the capacitor is switched out - so (as the name suggests) it's only being used when starting.

Some motors have two capacitors run and start. Since you only mention the one capacitor - a motor of this type would either have two housings or a combined housing for both capacitors.

You can test a capacitor if you have an ESR meter however they are expensive so it's usual to replace the capacitor to see if it's the problem. An old fashioned repair shop might be able to test it and the rest of the motor and/or fix it for you. The windings can also be tested e.g. do they have a low impedance or are they open circuit e.g. burnt out?
 

CHJ

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If the motor has a single Start/Run capacitor and no centrifugal switch then it is likely to be a 20 - 25Mfd capacity.

You need to get a RUN rated item with a working voltage in excess of 350volts (to cover the peak voltage of domestic 240 volt RMS)
 

Robbo3

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I now have a copy of the Brook Gryphon motor connection sheet courtesy of Peter at the Boleyn Workshop.
PM me your email address if anyone would like a copy.
 
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Samara

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Thank you all so much for the help and the important information for me. Then in no particular order but with thanks to you all, my follow on questions and comments:-
2 pole v 4 pole? How can I tell? Do I need to open the motor to see this?
Absolutely no marking on the old capacitor. Even carefully removed the maroon paint to see if any marks under it. The original supply colour was light green. A two wire in black rubber insulation protruding from the metal case suggesting the original unit to me. Only one capacitor on the motor which is externally mounted. A metal container with the bracket forming part of the outer cover, middle section when removed shows two end caps.
Been in touch with Peter who sent on wiring diagram which lists the part number of F590/420 but not sure which motor that is for the TEFC or PROT. He was very helpful on other questions. Thank you for the offer of the sheet.
Most of the pictures for Majors show a blue plaque under the headstock. I don’t have this just a lettering in the casting. The motor mount is different as well. Most of the motors I have seen in pictures have TEFC (totally enclosed fan cooled) stamped on the plate, mine has PROT. Other information on the plate is as follows:- 1 ph, 1 hp, 50 cycles, 50 c rise, 230/240 v, rating INT, F.L. amps per terms: 5.5, F.L. speed 2850.
 

Simon_M

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It’s 2 pole because the rotation speed is high. If it was low speed (half of 2850 rpm) then it would have been a four pole. May not be relevant to getting the right capacitor.

The speed of the motor is (mostly) how quickly the alternating current causes the motor to move around the poles and four poles requires twice the cycles (time) to rotate as much, so at half the rpm. Many induction motors run slower by about 1-2% because they “slip” a little.
 

Benchwayze

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Just for info :
My 1971 Model has a Brooks Gryphon, 1hp motor. Touch wood it's still running well.

John (hammer)
 

Samara

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It has been a real education and thank you for the knowledge. I had a chap look at the motor and it is fine to continue working, just need the capacitor. Good news from my point of view.
 

Rupert_Bear

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Hi, my maroon Major has the same motor, 2850rpm.
The capacitor is marked "60-80 UF (microFarad), 275V RMS". It looks too shiny to be original, but it works fine.
Regards,
Rupert
 
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Try this site:

Pyatt Woodworking

I haven't heard from or about Derek Pyatt for a while so I don't know the situation at the moment, but he is a fund of knowledge and has a lot of spares.

John (hammer)
I spoke with Derek a couple of weeks back - he's overrun with orders and queries 'cos of lockdown. Like me he's a Category "A" risk for Covid so isn't going out much if at all.
 
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