3 phase motor

[Duncan Bennett]

No problem, Archy.

I'm actually quite pleased with the way this has gone; i know i don't know much about three phase, but I feel vindicated when I see how interesting this thread has actually become and, if a guy like Tony can be slightly taken aback by the spec. of the motor, then how baffled was I going to be - justification enough for having made the post in the first place :0)

 

[Lilley]

i would use a C10 triple pole. C type to reduce tripping on start up

 

[Darkwood]

Tony I'm no expert on motors.

But you are right the 6.4A rating for a 2.2KW 3P motor is for a delta connected 230V supply.

For Star connected, 400v 3P 2.2KW motor the current will be 3.19A.

So a 6A c-type breaker will suffice with 1.5mm cable.

Check out my posts regarding mcb sizing for this motor, you'll be supprised and hes already shown plate in pic as 6.4amps.

 

[Knobhead]

Tony I'm no expert on motors.

But you are right the 6.4A rating for a 2.2KW 3P motor is for a delta connected 230V supply.

For Star connected, 400v 3P 2.2KW motor the current will be 3.19A.

So a 6A c-type breaker will suffice with 1.5mm cable.

You have to take power factor and efficiency in to account as well.

 

[Darkwood]

Quick question duncan... is the 1.5mm SY the supply from the mains or is it the cable linking motor up to control box?

 

[netblindpaul]

I suspect that is the "machine" rating plate, not just the motor?
It may have solenoid latches that are part of that current draw.

 

[Duncan Bennett]

Duncan note on your second pic.... SY cable has been utilised to supply motor... but i see the screen has been taped off, make sure you earth the screen as its a possibility if the cable is damage it may become live otherwise, and Note! on my mcb choice, alot of people question why i have picked mcb's alot higher than expected, i cross reference them to manu' guides of mcb's and recommended mcb in relation to motor size.... having said that a 2.2Kw would normally need a 16amp(b) or a 10amp(c); In your case the motor current FLC (full load current) is that of a 3Kw motor hence i have thus given the mcb rating for a 3Kw motor. Following this advice you will eliminate periodic nuisance trips due to inrush.

Yes on the sheath. In fact, there are no glands on the SY cable at all, at both ends it is taped off and pushed through a rubber grommet at both the control switch and isolator. I have them on my shopping list.

Thanks

 

[Darkwood]

I suspect that is the "machine" rating plate, not just the motor?
It may have solenoid latches that are part of that current draw.

Well spotted .... missed that one as it has the weight on it and by heck that one heavy motor, this changes everything if thats the case as the motor is prob 2.2kw standard thus a 16(b) or 10(c) will suffice.

 

[Darkwood]

So now we seem to have all the info duncan and as netblind has spotted; you have be giving us misguiding info and this power rating is the total ramp and not the motor rating itself, in this case then we can guess the motor is a 2.2kw and is standard ampage of 4.8amps.
So a 10amp (c) mcb , the SY will need earthed braiding too and your good to go.

 

[Duncan Bennett]

So now we seem to have all the info duncan and as netblind has spotted; you have be giving us misguiding info and this power rating is the total ramp and not the motor rating itself, in this case then we can guess the motor is a 2.2kw and is standard ampage of 4.8amps.
So a 10amp (c) mcb , the SY will need earthed braiding too and your good to go.

Sorry about that, it was all the info I had. Thanks again for all your help with this

 

[telectrix]

just to add to darkwood's comments. you need to obtain the proper SY glands. these are similar to SWA glands, but have a slot each side to terminate the "armour". you tease it out on both sides ( like a hercule proirot moustache, then squeeze it through the slots. trim off excess after fitting.

edit: just seen from the pics that it's italian. therefore it will be about as efficient as an ashtray on a motor bike, so current mayt be higher than expected. and like their tanks, it will probably run in reverse.:6:

 

[Duncan Bennett]

Cheers, Telectrix. I've used the glands before. Can't think what you're insinuating about italian workmanship; my Punto goes from 0-60 in under an hour!!!! Excellent performance!

 

[telectrix]

bloody. ell. that's quicker than my van.

 

[Engineer54]

Can someone help me with this?

I almost exclusively deal in domestic work, but I've been asked - by a mate - to install a car lift in his garage.

It's a three phase, 400v 6.4amp motor which outputs 2.2kW. I'm running from the Distribution board in swa to the control switch.

My question is, what size of 3 phase Circuit Breaker should i install at the board? Can I get away with 6amp breaker? Also, what's the story with B, C & D curves?

Thanks

Yes, it has a three phase distribution board - it's a factory unit. And yes, I realise it's notifiable. And thanks very much for taking the trouble to answer, my knowledge of three phase is written on my thumbnail.

I'm going to apologize to you Duncan, i wasn't in the best frame of mind last evening, not that is any excuse, just a jerk reaction to your personal comments to me!!

To be absolutely honest with you, when i first read your OP i took you to be a Electrical Trainee, that was going to take on work that he was not competent on. That was also the impression i got from your second above post and hence the comments i posted...

However, i am still a little surprised on you not understanding the different MCB type curves?? I'll also admit that i didn't particularly notice the discrepancy on the motor values given, but motor Tony highlighted that possible problem. ...lol!!

Anyway, i hope you accept my apology in this instance...

 

[Duncan Bennett]

I'm very pleased to accept your apology, Engineer, and would at the same time, like to offer my own in respect of my own tetchy response - you caught me after a few frustrating hours trying to research the information myself; I HATE being beaten on a question and so posting questions - as opposed to comments - on these boards is always, I feel, an admission of defeat on my part :-(

I felt I did have the answer - i'd calculated I=P/V and come up with under 6amps (I think Moses confirmed that later on). It was the fact that the plate said (I think it was) 6.4amps which threw me - I put that down to the motor and just wanted to confirm. As for the curves, I don't know why I missed that, I answered (Correctly) two questions on B, C & D curves in the SJIB exam I sat recently, but in my day (when wylex push button circuit breakers fitted into the old rewireable boards) the types were 1, 2, 3 & 4 :-(

As I said, I've been out of the game for a number of years now and am just trying to get back on the proverbial bike - only the bikes have changed; shiny new gears and aerodynamics. As I said, all respect to yourself and the other guys on here who do maths like it's a first language, however, I have no pretensions of getting my education up to that level. I'm having trouble enough with my Zs's & Ze's without trying to assimilate motor cosines. I hope though, that with the help of all you brainiacs, I'll at least be confident about adding a circuit to Mrs Blogs old CU and leaving her with the correct paperwork (and a bill).

Thanks for taking the time to write. It's much appreciated, and I'll look forward to getting to know all you guys a little better. As an aside, I learned more about motors yesterday than I have in the last 40 years

Now, while I'm on here, can anyone explain all this stuff about 'Earthing'??? Can you get it on a cash account at CEF???

...... only kiddin', Engineer

 

[Silly Sausage]

Whatever you do, don't bring up the subject of Earth Rods!