Any electrical engineers on here?

[Urga]

Hi
I've narrowed my fault with my planer thicknesser down to an earth fault within the motor. I'm getting continuity between the L & E and also the N & E from its feed cables. I've removed the motor entirely and have it on the bench. Again it will run fine without the earth connected, so am I right in assuming that either, 1. The L or N cable is shorting the motor body? Or 2. The earth cable from the windings is perhaps shorting to either L or N?
There is also a black cable from the motor, which I assume is from a thermal cut out switch?
My babbling aside, can anyone out there advise me on a logical way to troubleshoot the motor whilst on the bench? Also, in order to remove the Rotor from the stator to inspect the wiring, do I have to remove the pulley fully to enable a proper inspection? I dare say that this will become apparent as I attempt it, but just in case someone has some prior experience with these, it would be one less thing to have to remove.
Hope someone can help
Cheers
David

 

[HOJ]

To be honest the easiest way is to take it a rewind specialist, they will soon tell you what the issue is and give you a price to fix, unless its BER.

 

[MorrisWoodman12]

The fault you have is probably deep in the windings and a real problem to find and rectify.

I'm sure someone here recommended a rewind company in Edinburgh. I can't find my note of the company name so perhaps someone else can forward the information.

 

[Bingy man]

Maybe price a new motor and compare with a rewind , you seem to of covered the likely suspects so repair or replace and save your time and stress levels .. again though good luck and top marks for perseverance .

 

[deema]

The insulation on a coil has broken down it needs a rewind or recycling. It looks like a poor quality motor, just buy another.

 

[Sideways]

Chances of you getting a rewind for anywhere close to the cost of a decent new motor is slim.

 

[Urga]

I did and try to source a replacement motor price, but Charnwood have very little on their website in regards spares for this machine. Indeed Charnwood have not been at all helpful.
There are no specifications on the motor so replacement could prove problematic.
In all honesty I can't help thinking that, although the fault is serious, the issue could be caused by a relatively minor occurrence. The machine worked when I uplifted it, and this fault has happened either through offloading or cleaning.
The motor has good readings across both the starter and run windings, and I therefore doubt it would need rewound. The insulation on the other hand, I can not comment on as of yet.
The original owner stated that it sat mostly unused , and I have no reason not to believe that going on the condition of switches, capacitors etc.
I think I'll have to take the above advice and take this to a winding specialist, if for no other reason than to attain a diagnosis.
Thanks

 

[micropsyche]

I am an engineer (Australia) and……. I am a little concerned that your are test running the motor on the bench with the earth disconnected…… particularly when you suspect that there may be a short to earth from the windings. It’s your life and you you shouldn’t be doing such things when you need to ask for advice on how to fix it. I might suggest that you scrap and replace. A motor that size is not economically feasible to rewind. Sorry to be so direct, but in the circumstances, disconnecting the earth is a very dangerous move, touch the case and you could be the earth path.

 

[deema]

That is a bag of Sh*t motor, don’t waste your money. All you need to do is take a few measurements of the physical size of the motor to determine the frame size. The power rating from the machine spec and get yourself say a TEC motor. It’s probably a 71, 80 or 90 foot mount which is classed as B3.

With it only one capacitor, it’s the cheapest motor, least torque motor, so I’m guessing it’s a small feed motor. If it’s off the main spindle, well, all I will say is never buy that brand of machine again. If it is get a cap start cap run, that has two capacitors. If it is this motor it’s probably a 2.2 or 3KW L90 B3.

IEC Quick Reference Chart | James Electric

By law, it must have a plate on the motor giving sufficient detail to find a replacement.

 

[Urga]

That is a bag of Sh*t motor, don’t waste your money. All you need to do is take a few measurements of the physical size of the motor to determine the frame size. The power rating from the machine spec and get yourself say a TEC motor. It’s probably a 71, 80 or 90 foot mount which is classed as B3.

With it only one capacitor, it’s the cheapest motor, least torque motor, so I’m guessing it’s a small feed motor. If it’s off the main spindle, well, all I will say is never buy that brand of machine again. If it is get a cap start cap run, that has two capacitors. If it is this motor it’s probably a 2.2 or 3KW L90 B3.

IEC Quick Reference Chart | James Electric

By law, it must have a plate on the motor giving sufficient detail to find a replacement.

I believe it's a 1.5KW motor. There are 2 Caps, as per the picture, so it does have a run and start cap. There definitely isn't a plate on the outside of the housing. However, there may be something inside.
I dropped it off at a winding specialist today, and he was scratching his head regarding why it was going to ground. So it's not just me that's baffled.
I contacted Richard at Charnwood regarding a replacement motor and he quoted £250. I paid £500 for this machine, so this is quite a blow. If it didn't involve a 7hr return journey, I would have just returned it. But hey ho.
Can you recommend a good source for a suitable motor? I am worried about having to get the exact size, complete with a mounting plate etc, so it's a simple bolt in with no worries about new belt sizes etc.

 

[Urga]

I am an engineer (Australia) and……. I am a little concerned that your are test running the motor on the bench with the earth disconnected…… particularly when you suspect that there may be a short to earth from the windings. It’s your life and you you shouldn’t be doing such things when you need to ask for advice on how to fix it. I might suggest that you scrap and replace. A motor that size is not economically feasible to rewind. Sorry to be so direct, but in the circumstances, disconnecting the earth is a very dangerous move, touch the case and you could be the earth path.

Thank you for your concern.
There's nothing new in people trying to repair things for themselves, especially when money is tight.
Regarding working safely. Although I'm no electrical engineer, I have a basic understanding of electricity. I understand what ground means and when on the bench the motor was started and shut instantly whilst the earth was disconnected. I also was wearing thick rubber gloves, so I didn't become the ground, during this test.
Whilst the motor was in the machine and I had the earth disconnected, I also made sure I was well insulated and had the test meter on various bare metal surfaces. Interestingly, no AC voltage readings were given anywhere? I know RCD's need very little current to trip them, but I take your point, in that the machine could be rendered live during this test.

 

[Sideways]

Can you recommend a good source for a suitable motor? I am worried about having to get the exact size, complete with a mounting plate etc, so it's a simple bolt in with no worries about new belt sizes etc.

I recently priced a 2.2kW motor at around £230 so you will get a 1.5kW for less.
That will buy you a TEC branded motor made in Shanghai.
Single phase twin capacitor is no problem.
Having bought and fitted several, I can vouch that they are better than the motor fitted to your Charnwood.
Prices of motors have increased dramatically in the last couple of years - almost doubled - but contact bearing boys for a competitive price.

You need to study a little around how IEC standard motor frame sizes work.
There are face / flange / foot mount options. You will need a foot mount also termed a B3 almost certainly.
The frame size standardises the spindle diameter, height of spindle above the feet, position of mounting holes, and overall dimensions such that motors can be readily swapped out.
Read the reference provided by @deema above.

As he says, you probably have an 80 frame or 90 frame size given that it's a 1.5kW motor. You also need to know if it is 2 pole (2800- 3000 rpm) or 4 pole (1400-1500 rpm). That's why there should be a plate on the motor. The fact that there isn't doesn't speak well of it. Perhaps a question for Charnwood.

Also, measure the diameter of your existing spindle. It looks like it might be stepped down. Another non standard and bad feature if so. The solution is to buy a replacement pulley to fit a new standard motor. They are cheap but a taper lock pulley and taper lock bush will add £10 to £20 to the project.

HTH

 

[Urga]

I recently priced a 2.2kW motor at around £230 so you will get a 1.5kW for less.
That will buy you a TEC branded motor made in Shanghai.
Single phase twin capacitor is no problem.
Having bought and fitted several, I can vouch that they are better than the motor fitted to your Charnwood.
Prices of motors have increased dramatically in the last couple of years - almost doubled - but contact bearing boys for a competitive price.

You need to study a little around how IEC standard motor frame sizes work.
There are face / flange / foot mount options. You will need a foot mount also termed a B3 almost certainly.
The frame size standardises the spindle diameter, height of spindle above the feet, position of mounting holes, and overall dimensions such that motors can be readily swapped out.
Read the reference provided by @deema above.

As he says, you probably have an 80 frame or 90 frame size given that it's a 1.5kW motor. You also need to know if it is 2 pole (2800- 3000 rpm) or 4 pole (1400-1500 rpm). That's why there should be a plate on the motor. The fact that there isn't doesn't speak well of it. Perhaps a question for Charnwood.

Also, measure the diameter of your existing spindle. It looks like it might be stepped down. Another non standard and bad feature if so. The solution is to buy a replacement pulley to fit a new standard motor. They are cheap but a taper lock pulley and taper lock bush will add £10 to £20 to the project.

HTH

I appreciate the input and will investigate my options based on your recommendations. Thank you

 

[Skeety]

My first thought was as mentioned above that the dilectric in the motor has broken down.

OK, probably a stupid question but here goes:

What do you have it plugged into? Is the breaker an MCB or RCBO? Have you run a similar type of device in there before? As it's tripping the house also i would suspect that it's an MCB, if so what type?

My thought being that it may be the inrush current tripping the breaker.

Jon.

 

[porker]

If there is continuity between live and neutral to earth then there is an earth fault as reported by the OP rather than an inrush issue

 

[Urga]

My first thought was as mentioned above that the dielectric in the motor has broken down.

OK, probably a stupid question but here goes:

What do you have it plugged into? Is the breaker an MCB or RCBO? Have you run a similar type of device in there before? As it's tripping the house also i would suspect that it's an MCB, if so what type?

My thought being that it may be the inrush current tripping the breaker.

Jon.

Jon
I think I ruled that out very quickly. The box has mcbs and a rcd which is wired to a mcb in the main box in the house. I understand that when the rcd is tripped( not a mcb) in the garage, the house(feed)rcb will trip first.
I've had experiences with inrush current with my lighting when I fitted several led batons. This was easily solved with changing the mcb to a type C curve

 

[Skeety]

Worth a try.

 

[deema]

It MUST have a rating plate on the motor, it’s not an option for a motor to be supplied without one. Speak with Charnwood and ask some very pointed questions.

If it’s got a start cap, there is the possibility that the switch to change it from the start to run cap is shorting.

I would take the back of the motor off and have a look at the dynamic switch.
I thought it was just a single cap motor as that’s all you’ve got wired in. A cap could also have blown and shorted to the case. (I’m assuming you’ve already checked that?)

The motor is still a boat anchor!

 

[Spectric]

Again it will run fine without the earth connected, so am I right in assuming that either, 1. The L or N cable is shorting the motor body? Or 2. The earth cable from the windings is perhaps shorting to either L or N?

You need to get the motor checked by someone who knows about motors, but not worth getting it rewound so might just be as easy to get a new motor.

I've had experiences with inrush current with my lighting when I fitted several led batons. This was easily solved with changing the mcb to a type C curve

I hope you measured the loop impedances to ensure the wiring can take the higher current during a fault condition, type B needs 3 to 5 times rated current to disconnect whilst a type C needs 5 to 10 times rated current which means a 16 amp device might require 160 amps compared to 80 amps for the type B. Having seen the results where people just change a protective device it is always an eye opener, no different to wrapping a fuse in foil. Changing any protective device is a change in original design and therefore should only be done by a qualified sparky with the right test equipment who can provide a certificate of safety.

 

[Spectric]

It MUST have a rating plate on the motor, it’s not an option for a motor to be supplied without one.

I have seen cheap asian motors where the plate is nothing more than a sticky label so could easily have just peeled off and is a good reason to just fit a new better quality motor if the mechanicals align !