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Hi everyone

I purchased a bench polisher which looks to have come from China. It says its 220v single phase and should work fine in the UK. The power cable has 4 wires in it so I'm confused how to wire a standard UK plug. I have attached a photo of the cable.

Any advice would be much appreciated.
 

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Strima

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Looks like a forward and reverse switch is required. What do the manufacturers instructions say? Do you have a web link for this machine?
 

Spoon

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Welcome to the forum mate.
The motor should have a information plate on it, with the spec of the motor. Take a pic and post it up. Post a pic of the motor as well. Are there any controls with the motor?
 
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  • #5
Looks like a forward and reverse switch is required. What do the manufacturers instructions say? Do you have a web link for this machine?
Hello thank you so much for replying, please find attached images of the machine and some specs, please not its a 220v machine.
 

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  • Thread Starter Thread Starter
  • #6
Welcome to the forum mate.
The motor should have a information plate on it, with the spec of the motor. Take a pic and post it up. Post a pic of the motor as well. Are there any controls with the motor?
Hi thanks for replying, ive attached images of the machine. The machine is a 220v machine and is supposed to be single phase. It didnt come with a plug, the power cable has 4 wires which is confusing me.
 

Strima

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That's a surface grinder not a polisher so you won't be getting many shiny things from that...

You need a motor reverse switch installing. Something like: Motor Reversing Switch single or 3 phase 25, 32 or 63amp 4 Pole Lathe car lift | eBay - https://www.ebay.co.uk/itm/Motor-Reversing-Switch-single-or-3-phase-25-32-or-63amp-4-Pole-Lathe-car-lift/331117252512?hash=item4d18204fa0:m:mwsgmUcdOA3BgKppYa0rovQ&var=540332832124

Ideally you need someone experienced with motor controls to install this for you.
 
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  • #10
That's a surface grinder not a polisher so you won't be getting many shiny things from that...

Ideally you need someone experienced with motor controls to install this for you.
H Strima thanks again for replying, I was wondering does it really need a motor reverse switch as it has a FORWARD/REVERSE switch already at the front of the machine.
 

Spoon

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1565988548724.png

1565988601923.png

It seems to state the motor needs 380V. You will only get this if the machine has something like an inverter in it.

Can you take a pic of the plate on the motor.
1565988759738.png

This might give us more info.
 
Just wondering if that motor is three phase, 380v in star and 220v in delta. Your motor maybe pre wired for 220v delta, possibly.
 

Spoon

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Looks like the only thing you can do is get inside the machine and see where the four wires wire to.
 

James

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If you are still unsure, I am in brownhills on Monday and in the jewellery quarter on Tuesday and Wednesday
I will be able to either make it work or tell you what’s wrong with the specification.
 
The motor doesn't show a capacitor but could be split phase (single phase) but I suspect it is three phase and there is no reason for it to be reversible. The image of the machine does show a two position switch so maybe reverse capability is built into it.
 

Megawatt

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Im really really surprised and very pleased with all the time and help you have all given me. I really appreciate all your replies.

This may be a stupid question, but if we assume the cable could be wired to an American 4 Pin plug, could it be wired the same way on a UK plug but ignoring the green (ground)??

@Megawatt @Spoon @westward10 @James the Spark1976 @Strima
Yes the 4th wire as y’all know is just an equipment ground the 3 prong is the same as my stove. It’s 220vac single phase and the neutral is mainly for the clock and timer. I’m trying to research it for gingsing
 

Spoon

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May also be worth it to try and find out what frequency this has been manufactured for. 50Hz, 60Hz or both?
 

Megawatt

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Yes the 4th wire as y’all know is just an equipment ground the 3 prong is the same as my stove. It’s 220vac single phase and the neutral is mainly for the clock and timer. I’m trying to research it for gingsing
It also could be 220vac with no neutral the 3rd wire being the ground
 

Megawatt

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Hi everyone

I purchased a bench polisher which looks to have come from China. It says its 220v single phase and should work fine in the UK. The power cable has 4 wires in it so I'm confused how to wire a standard UK plug. I have attached a photo of the cable.

Any advice would be much appreciated.
Jinsingh do you have a brand name and model number
 
If possible can you remove the motor terminal cover and show the connections within.
 

Spoon

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Hi Megawatt

I only have the image and details from the advert. It was purchased via Aliexpress which is a Chinese wholesale website.
Where did you get the pic of the 4 wires? (Your original pic). That doesn't look like it's from an advert.
 
It looks like a US dual phase lead, (what they call 3 wire) though the yellow wire should be white and should not be connected anyway.
 

Lucien Nunes

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This may be a stupid question, but if we assume the cable could be wired to an American 4 Pin plug, could it be wired the same way on a UK plug but ignoring the green (ground)??
No, we don't use that type of power in the UK, it's specifically N. American. I think the references to US power configs here are misleading, there's no reason to think your machine is wired that way. The Chinese 3-phase colours are red/yellow/green which matches your cable (although I think neutral is more often blue now). I suspect one of two things:

a) they sent you a 3-phase machine instead of the single-phase one you ordered.

b) they converted it to single-phase but left the 3-phase mains cable attached.

Either way, they shouldn't sell equipment in the UK with that cable.

We need to see:
1) Motor rating plate
2) Inside motor terminal box
3) Where the cable terminates inside.
 
  • Thread Starter Thread Starter
  • #37
Hi everyone

I am really grateful for all your time and help. Please find attached photos of the motor, wiring, and back of the machine.

Hope it make sense to you guys.
 

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Agreed the capacitors weren't clear from the first pic. Cap start and run.
 

Lucien Nunes

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OK, the motor is definitely single phase, but they have left the original 3-phase cable with chinese colours attached. You will need to inspect where the cable terminates, and possibly make some continuity measurements with a multimeter, to find out which colours they have used for line, neutral and earth as it's now impossible to assume anything. In fact it would make more sense to replace the cable to the input terminals as the existing one is totally unrecognised in the UK.

In truth, now would be a good time to call an expert to look at it. Or even call the supplier, although I am not sure whether you will get an intelligible answer that way! However, if you're up for more investigation, do you have a multimeter and are you familiar with using it to take resistance measurements?
 

Lucien Nunes

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Doesn't make much difference MW, we can see the line and neutral going into the motor, but we don't know for certain which cores of the input cable those line and neutral correspond to, as there's a switch and possibly a junction box in the middle. We can't trust that the colours going in are the same as the ones coming out to the motor as it has been altered.
 

Megawatt

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Doesn't make much difference MW, we can see the line and neutral going into the motor, but we don't know for certain which cores of the input cable those line and neutral correspond to, as there's a switch and possibly a junction box in the middle. We can't trust that the colours going in are the same as the ones coming out to the motor as it has been altered.
Just trying to help since he came to us for help I understand what you are saying but it drives me crazy not being able to get his motor running. I’ve been on YouTube researching but you are right we can’t just assume anything
 
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  • #49
When you took the cover off the motor did it have a wiring diagram inside the cover
Hi

No wiring diagram anywhere at all I will second check to see if any numbers on wires. I will also open the base and see if I can check how the power wire joints the cable running to the motor
 

James

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Hi

No wiring diagram anywhere at all I will second check to see if any numbers on wires. I will also open the base and see if I can check how the power wire joints the cable running to the motor
It looks from the picture that it is configured for single phase.
Presuming it’s 230v or there about, I would expect this to be a half hour job for anyone who is competent and has a good understanding of ac motors and there configuration for single phase use.
Where in Birmingham are you?
I might be passing you on Monday or Tuesday as I am working that area early week,
 
  • Thread Starter Thread Starter
  • #51
It looks from the picture that it is configured for single phase.
Presuming it’s 230v or there about, I would expect this to be a half hour job for anyone who is competent and has a good understanding of ac motors and there configuration for single phase use.
Where in Birmingham are you?
I might be passing you on Monday or Tuesday as I am working that area early week,
Hi

I am just north of Birmingham near West Bromwich
 
  • Thread Starter Thread Starter
  • #54
Hi Guys

I've managed to take photos of how the cable from the motor connects to the power cable.

It looks like the black wire is connected directly between both cables, green wire isnt used, Red and yellow wire is connected via switch.
 

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  • Thread Starter Thread Starter
  • #55
Hi Guys

I've managed to take photos of how the cable from the motor connects to the power cable.

It looks like the black wire is connected directly between both cables, green wire isnt used, Red and yellow wire is connected via switch.
Photo from other side of switch
 
They are useful pics. You are going to need professional help with this because the unit appears not to be earthed unless the blacks are earth, where do the blacks go. The greens appear to have been at some time connected to the switch.
 
  • Thread Starter Thread Starter
  • #58
They are useful pics. You are going to need professional help with this because the unit appears not to be earthed unless the blacks are earth, where do the blacks go. The greens appear to have been at some time connected to the switch.
Looks like the black wire is connected between cables but isnt connected at the motor see image
 

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  • #60
Do you guys think this machine is self earthing? And just need to ground the chassis please see image.
 

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netblindpaul

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jinsingh, seriously are you going to use this in a business, or for DIY at home?

As far as protective conductors go, the Chinese have weird ideas, I've spent time out there teaching a company to comply with EU requirements.
Their socket outlets are not necessarily earthed, so they fit a separate point to earth the equipment back to an earth marshalling terminal mounted on the wall.

As it stands.
Either way, this equipment is not legal for use in the EU, nor is it legal to import.
If this is going into a business, I seriously suggest you re-think, as the offence is criminal, not civil.
If it is for DIY, just beware that it has been imported illegally, and would be illegal to sell second hand should you feel so inclined.
It would be likely that it would void any house insurance claims if something went wrong.
 
Seems a company called AliExpress market these but the UK site doesn't have them so it must has been obtained outside of the EU.
 
It would be unwise to give advise on how to connect the machine because if it is not earthed it is not safe. Have you purchased it as a new machine or second hand/used.
 

Strima

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That is a proper lash up, I would send it back as it's not safe or fit for use.

If they have lashed the electrics up what else have they lashed up, I wouldn't want to be near it when that wheel gets up to speed.
 

James

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It is typical of a cheep Chinese import machine.
I would expect it to cost more to bring up to uk standards than you have paid for it.

it also looks as though it may have no means of earthing, although that would have to be confirmed.

I doubt you will find a reputable electrician that will be able to sort it out and connect it up whilst achieving a suitable level of machine safety unless you are willing to pay a lot of money.

I am seeing amongst other things

lack of guarding
no emergency stop button
all signage is in a foreign script so cant be read.
probable that m/c is not earthed
cables do not appear to be going through correct glands
it is undoubtedly not CE marked.

I think you have 2 choices

1. send it back for a refund
2. find a guy down the pub that knows about electric stuff and buy him a beer. (p.s. this would be against my advice and the majority of the comments above)
 

Lucien Nunes

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I think it is earthed. The blacks of the supply and motor cables disappear out of shot near the switch, I expect to a couple of tags under some convenient screw. The supply cable has the three Chinese phase colours plus a black earth.

But I like Davesparks' comment which sums it all up, it's pretty likely to be unsafe in ways more insidious that having funky colours in the mains cable. OP, sorry, don't mean to be disparaging, but on here we tend to say it as we see it.
 
B

Bobster

Even if you could get this unit to work.

There is a reason surface grinders are not bench tools. The vibration and accuracy need to be compensated for, so usually are quite heavy units.

So I imagine, even if you're willing to spend a large (an it would be large) amount of money to bring it in line with UK safety requirements, the machine probably wont be very good.
 

marconi

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For the OP: what I have written below is for my electrical colleagues on the EF. You need someone to rewire afresh the whole machine which at the moment is an unsafe lash-up.

I have been studying the images the OP provided and have an alternative view on what has been wired.

Some assumptions:

1. The work lamp is 220Vac.

2. The motor is a three phase squirrel cage motor which can be wired 380V star or 220V delta.

3. The original manufacturer's wiring was for 3 phase operation at 380V and the TPDT centre off rotary switch enables Reverse - Off - Forward rotation of the motor - there are clues to this if you study the rotary switch images, the classic positions of the 4 solid links and the chopped of blue and green wires. The motor was wired as star.

4. I reckon (cannot be certain) but the original machine lead was 3 wire and earth. The lamp obtained its 220V ( = 380/1.713) by connecting across a line and the virtual neutral at the start point of the motor. If the lead was 4 wire and earth then an external neutral is provided which the lamp can use.

5. On one of the specification plate images it says the machine is for 380V, but at the bottom right 'Voltage - 220V needs to be customized and pay extra...'

I think then that the original 380V 3 phase star motor has been 'customized' to run on 220V single phase. The ability to swap motor direction has been disconnected and all the rotary switch does now is switch on/off the L and N to the motor. What the black wires does at the rotary switch I do not know without seeing what happens where it is sleeved with white sleeving - is it attached to the metalwork to be the cpc? For China this would be the wrong colour for the cpc - they use green/yellow - black or blue are reserved for the neutral.

To operate at 220V the motor must be wired as delta. The 'customization' is to attach the black plastic box over the original motor terminal housing and place a capacitor to the left and right as shown. These capacitor are for start and run in the Steinmetz type 2(delta) circuit, where Cr and Cs are what you might expect ie:

1566384258559.png

What you see is a switch which introduces the start capacitor during run up and then disconnects it at operating speed. The grinder motor has no internal switch to do this and the rotary switch cannot be co-opted to do it. The customization overcomes the absence of the switch by wiring the motor as the red circuit drawn below which keeps Cs in circuit . The way winding W is fed via winding V reduces the potential across W to prevent it overheating when permanently fed via the low series reactance of Cs which although its value cannot be seen is normally of the order 200uF. By contrast the run capacitor is 25uF so a higher series reactance. Tracing out the machines current wiring one arrives at the circuit I point to in the middle of this scribbled diagram, where LN are across U:



chinamotor.JPG

I have not had time to think about whether the rotary switch can be used to provide REV- OFF-FWD control - perhaps others might think on this.
 
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