Motors and Star Delta Question

[dlt27]

Hi and thanks for any replies.
I am predominantly an install electrician and don't have a lot of experience dealing with motors so any help would be greatly appreciated.
I have been asked to connect a CNC machine, a dust extractor and a pump.
The CNC is straight forward as it is just connected to a rotary isolator, however the pump and extractor are just free standing motors and the name plates are in Chinese. I know the pump is 5.5 KW 3 phase and the extractor is 3KW 3 phase.
1. Am I right in thinking both should be wired through DOL starters with I think when calculated results in a 8.5A and 4.8A overloads with 0.9 power factor correction. (Guy who sold machines said rotary isolators were adequate for starting the motors)
2. Up to what size motors can a DOL starter be used.
3. How do I determine if they should be connected in Star or Delta as can't tell from name plate (What would happen if I connected them up wrong, ie connect in Delta and should be Star or vice versa?)
4. Am I right in thinking a DOL starter should always be used with motors because it provides protection to windings on start up and also it prevents motor restarting on power failure.
5. How do you determine if a Star Delta starter should be used with a motor?
Thanks again if you have got time to explain.
I

 

[David Prosser]

Motors of this size will need proper start circuits with overload protection. I don't think a rotary isolator will cut the mustard. I bet if it needs a pump and extractor that big the machine drive motor will need proper protection as well.

Did it not come with a starter or control panel or would there be any chance you could track down it's original owner to find out if it's available?

Also I would go back to "the guy" and give him a slap. If he doesn't know anything about motor control then tell him to S.T.F.U. with his dodgy info.

 

[westward10]

Geez that is an open ended question, there are multiple ways of starting a SCI motor DOL, SD, VFD and others with each being suitable for the demands on the motor and the type of drive required.

 

[dlt27]

The CNC is a complete unit with connection terminals for the supply. It was just the extract and pump motors that don't have starters etc. They are independant machines to the CNC so I just thought I could connect them up through a rotary isolator and a dol starter.
They are new machines and when I asked the seller how to wire up he just said he doesn't have anything to do with the electrics and he said I was the electrician not him.....

 

[dlt27]

Just remembered I took pictures of the plates. Am I right in thinking they are connected in star? 380v? Thanks again

 

[LeeH]

hmmmm, no CE mark to be found on both those motors...

Not fit for purpose according to the low voltage directive.

 

[Pete999]

hmmmm, no CE mark to be found on both those motors...

Not fit for purpose according to the low voltage directive.

Hi Lee, not doubting your statement regarding the "low voltage directive" in any way, but any chance toucould link the chapter/passage you are referring to, just interested that's all.

 

[davesparks]

380V doesn’t really sound like a motor intended for the UK market, or at least not one started by simple DOL or similar. You’ll need something that can give the motor the voltage it needs.

As to whether you start it DOL or by other methods it can depend on the incoming supply.
If the incoming supply is big enough to cope with it then you can theoretically start any size motor DOL, but whether you should or not, or whether it’ll break the machine is another question.

 

[westward10]

I agree with DS that will either run at 380v in star and probably at 220v if you connected it delta but not dol from a straight on supply in this country.

 

[dlt27]

This is a lot more complex than I thought.
The machines are all fed from a 3 phase transwave 22kw converter. (no 3 phase supply to building)
So am I right in thinking the motors can be supplied via a dol starter with overloads set at flc and connected in star or am I totally wrong and shouldn't get involved. Unfortunately like I said my background is more install work.
From nameplate if there is no drawing how do you determine if motor should be connected in star or delta?
Thanks to all for comments and if anybody can explain in layman's terms it would be appreciated.

 

[elsparko]

the 3kw plate seems to show star connections

i was under the impression that rotating machinery needs contactors for start up and emergency stop local to machine for when the farmer gets his tie stuck in the rotary parts

 

[LeeH]

Hi Lee, not doubting your statement regarding the "low voltage directive" in any way, but any chance toucould link the chapter/passage you are referring to, just interested that's all.

Hi Pete, as I understand it all electrical goods have to be.

CE Marking Electrical Equipment Guidance - Low Voltage Directive - http://www.cemarkingassociation.co.uk/electrical-equipment/

 

[LeeH]

the 3kw plate seems to show star connections

i was under the impression that rotating machinery needs contactors for start up and emergency stop local to machine for when the farmer gets his tie stuck in the rotary parts

Not always. Some machines use ‘safe torque off’. No contractors necessary.

 

[Pete999]

Hi Pete, as I understand it all electrical goods have to be.

CE Marking Electrical Equipment Guidance - Low Voltage Directive - http://www.cemarkingassociation.co.uk/electrical-equipment/

Thanks Lee I thought that would be the reply, cheers anyway.

 

[dlt27]

Dol starters have stop starts on them so doesn't that satisfy emergency switching?.
Aren't dol starters just contactors with overloads built in?
I also read up on CE marking. I will let customer know!
I am meeting supplier of machines Wednesday so that should be interesting.
Thanks again

 

[LeeH]

Dol starters have stop starts on them so doesn't that satisfy emergency switching?.
Aren't dol starters just contactors with overloads built in?
I also read up on CE marking. I will let customer know!
I am meeting supplier of machines Wednesday so that should be interesting.
Thanks again

Google functional safety. What is required is based on a risk assessment and SIL equations that would make my head explode.

 

[Spoon]

Contact the Chinese manufacturers, I'm sure they will be happy to send you a CE sticker you can put on the motors..

Don't touch the motors that are not CE. If something goes wrong then it's your head on the block.

 

[Darkwood]

Connecting thousands of machines in my time I can tell you now that that machine is not designed or built for sale in the UK, I suspect it has been sourced direct from China with no interim seller thus it is still plated in Chinese and you have next to no instruction for the electrics which if it were to comply should provide you with all the necessary info of how to connect it all up, fuse sizing etc.
The motors and machine will more than likely require a step down TX and I would advice against direct connection to the mains.
Given you also have expressed the supply is converted single phase you need to look into the limitations of the converter and see if it will handle the inrush and on that note the single phase supply itself needs to cope too.
As a first step into this kind of work I would strongly advice against taking on this particular job, their are too many unknown variables here that you probably couldn't answer.

I would probably at a quick guess be looking at a multi-tapped TX with 380v output for the machine.
I would be considering VSD's controls for the motors that way you can program the parameters of the motors and run it then off the 400v supply, this will also reduce inrush issues on your 1-3ph supply converter.

I personally would also be concerned initially about the quality and safety of this product, as it has no CE approval it is highly unlikely to meet our safety standards and anyone using it or asking others to use it could be in breach of H&S laws, if the machine does indeed have a high standard of safety and does meet our standards but just lacks paperwork then it should be assessed and given a CE mark by a third party before use.... given I guess it has been bought cheap then I would be surprised if it met the standards and received a CE stamp.

As you are the person connecting up the machine and designing and installing the controls for the motors then you yourself take on responsibility regarding the machines compliance as it does not have the required CE approval - Good Luck! ... I recommend you walk away from this one.

 

[RWJ]

Sometimes you have to say no. If the customer doesn't respect that, they're not worth it, so walk away.

 

[elsparko]

my mum ordered a phone from china, it worked for all of 3 days, the chinese didnt even want the phone back but refunded

i have a customer that wants to re-use some downlights on a £110k extension, the joiners were less than cautious when taking down the plasterboard, most of them are smashed, i dont know how to break the news to these millionaires that they may have to spend an extra couple of hundred.