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3 phase help needed
oadamo - 9/12/09 at 10:19 PM

hi i need a bit of help, on the picture is the way its set up at the moment but ive got to use this supply to power an invertor. could i take the supply out of the middle breaker and run to the new invertor. the breaker is the right rating but wtf are the other breakers for and why 2 feeds to the motor lol. oh the middle breaker has an extra 3 wires i think there white bule and red that feed the bottom of it.

adam


[Edited on 9/12/09 by oadamo]

paulf - 9/12/09 at 10:26 PM

It looks as if that may be a star delta starter or else a 2 speed motor, what is it on?.If a star delta it is to start the motor in 2 stages to reduce start up current.
An inverter would need to be fed from 1 phase and neutral if single phase input type , have you got a 4th wire for neutral in the incoming cable?
Paul.

MakeEverything - 9/12/09 at 10:27 PM

The configuration you have currently is a star / delta starter, which is a changeover contactor to reduce starting current.

To install an inverter, youll need to strip out the contactors, and just have one.

AdrianH - 9/12/09 at 10:28 PM

Couple of questions, how big is the motor and is it duel speed?
This is my take on what you have drawn.

The three wires in the bottom are the 415 input to my mind.

The motor has 6 terminals because there are three separate windings and the 6 terminals are really each end of the three windings.

Now sometimes they can be used in star configuration to start and then switch to delta to run. But that would normally have been on large motors of several tens of horsepower.

I suspect you have a twin speed, 3 phase motor, with one set at one speed another other set faster.

Old lathes such as ward used to use multispeed motors etc.


Adrian

must type faster!

[Edited on 9-12-09 by AdrianH]

oadamo - 9/12/09 at 10:36 PM

to quick lol, yes there is a neutral wire there.
the motor is about 2 foot sq and pulls 23amp.
the fuses are 63 amp, and the breakers are 18.5kw/25hp. the new motor is 18.5kw and 25hp but running with a new inverter. could i leave the breakers as they am but just wire the new inverter to the top of the middle breaker.
thanks for your help adam

[Edited on 9/12/09 by oadamo]

AdrianH - 9/12/09 at 10:51 PM

Again having a bit of a guess here.

The inverter could well be 415 V three phase input and if supplied with the motor I will also assume it is wired for it. If not defiantly speak with the supplier and ask them to do it.

Most inverter drives have soft start ramp up and ramp down to stop. Emergency stop is done with external brake resisters. At least it is done that way on my a lot smaller set up with panasonic inverter.



If that is a picture of the old setup how many terminals on the new motor?

If I have assumed correct then I would remove all breakers and go directly from the fuses to the new inverter input.

Never, ever stop the motor by switching off the power . Your inverter drive should have start and stop buttons to control it all.


And at the fuse ratings and current drawn that you have on that motor, forget all we are telling you and get an industrial electrician in to sort it out.

That type of current will melt cables, blow panels off walls and is not forgiving if an error is made.

Adrian

MakeEverything - 9/12/09 at 10:52 PM

quote:
Originally posted by oadamo
to quick lol, yes there is a neutral wire there.
the motor is about 2 foot sq and pulls 23amp.
the fuses are 63 amp, and the breakers are 18.5kw/25hp. the new motor is 18.5kw and 25hp but running with a new inverter. could i leave the breakers as they am but just wire the new inverter to the top of the middle breaker. what would i need to wire the new motor in star or delta is delta with the strips running in line or across the pins.
thanks for your help adam


Sounds to me like you need to leave it alone and get an electrician. If you get it wrong, you have a potential fault current to produce a rather disturbing bang, phase to phase.

MakeEverything - 9/12/09 at 10:55 PM

quote:
Originally posted by AdrianH
Again having a bit of a guess here.

The inverter could well be 415 V three phase input and if supplied with the motor I will also assume it is wired for it. If not defiantly speak with the supplier and ask them to do it.

Most inverter drives have soft start ramp up and ramp down to stop. Emergency stop is done with external brake resisters. At least it is done that way on my a lot smaller set up with panasonic inverter.



If that is a picture of the old setup how many terminals on the new motor?

If I have assumed correct then I would remove all breakers and go directly from the fuses to the new inverter input.

Never, ever stop the motor by switching off the power . Your inverter drive should have start and stop buttons to control it all.


And at the fuse ratings and current drawn that you have on that motor, forget all we are telling you and get an industrial electrician in to sort it out.

That type of current will melt cables, blow panels off walls and is not forgiving if an error is made.

Adrian


Any half experienced sparks should be able to swap the star delta with the inverter.
Some inverters are aw bitch to set up though, and require a specific programmer.

oadamo - 9/12/09 at 11:01 PM

yes the motor is 3 phase and the inverter is the motor is a brand new one with 6 connections in it with the metal tags for star and delta. the pic is the old setup. ive got to program the inverter yet
adam

quinnj3 - 10/12/09 at 11:33 AM

My advice is to leave it to a sparky to sort out. 415v is not something you want to be messing about with especially if the system is just protected by 63A fuses, you would have no chance of survival.

This is a relatively easy setup for an average skilled industrial electrician but my advice is to leave it to the pros on this one.
Normally I would encourage a bit of diy on minor electrics but not this time. I know this is of no help but take it into consideration at least.

wilkingj - 10/12/09 at 01:06 PM

240 volts Single phase, hurts when touched
415 Volts Three Phase will KILL.

If you are not a qualified electrician, then I would leave it to an expert.

Is your life worth £500 (for an electrician to do it properly)??

SteveWalker - 10/12/09 at 01:27 PM

quote:
Originally posted by MakeEverything
quote:
Originally posted by oadamo
to quick lol, yes there is a neutral wire there.
the motor is about 2 foot sq and pulls 23amp.
the fuses are 63 amp, and the breakers are 18.5kw/25hp. the new motor is 18.5kw and 25hp but running with a new inverter. could i leave the breakers as they am but just wire the new inverter to the top of the middle breaker. what would i need to wire the new motor in star or delta is delta with the strips running in line or across the pins.
thanks for your help adam


Sounds to me like you need to leave it alone and get an electrician. If you get it wrong, you have a potential fault current to produce a rather disturbing bang, phase to phase.


The electrician (fully qualified and experienced, but totally stupid) where I used to work, made a very satisfactory bang when he turned on the power to a 3 phase, 11kV 2.5MW motor (yes that's right megawatts) while there were still earthing bars across the phases and people working on the skid. The local breaker; the breaker in the distribution room; the Norweb breaker in the distribution room; the breaker in the substation and the breaker supplying the substation all tripped. I don't know what damage was done, but the factory and offices (500 employees); other nearby businesses and the local housing estate were all without power for over three hours!

oadamo - 10/12/09 at 09:36 PM

thanks all for your help its all done now and fully working there was a 100 amp breaker on the wall in a control box that went to the fuses so i wired off the fuses.
adam

[Edited on 10/12/09 by oadamo]

MakeEverything - 11/12/09 at 11:33 AM

quote:
Originally posted by wilkingj
240 volts Single phase, hurts when touched
415 Volts Three Phase will KILL.

If you are not a qualified electrician, then I would leave it to an expert.

Is your life worth £500 (for an electrician to do it properly)??



Actually, the voltage wont kill you, but the current will. It only takes 250mA to kill you if you get hit at the correct time. All to do with timing and your heart beat. 250mA is enough to send the heart out of sine, effectively causing a heart attack.

Just make sure the fuses are of the correct size for the cabling and the inverter. If the cable is rated at 63A (i forget my sizes currently) and is fed by a 100A fuse, the fault current (or max load current) could cause a fire or cable fault.

This exercise is called "Discrimination", and makes sure that all the fuses are the correct size and that breakers are set at the correct settings.

wilkingj - 11/12/09 at 12:18 PM

quote:
Originally posted by MakeEverything
quote:
Originally posted by wilkingj
240 volts Single phase, hurts when touched
415 Volts Three Phase will KILL.

If you are not a qualified electrician, then I would leave it to an expert.

Is your life worth £500 (for an electrician to do it properly)??



Actually, the voltage wont kill you, but the current will. It only takes 250mA to kill you if you get hit at the correct time. All to do with timing and your heart beat. 250mA is enough to send the heart out of sine, effectively causing a heart attack.

Just make sure the fuses are of the correct size for the cabling and the inverter. If the cable is rated at 63A (i forget my sizes currently) and is fed by a 100A fuse, the fault current (or max load current) could cause a fire or cable fault.

This exercise is called "Discrimination", and makes sure that all the fuses are the correct size and that breakers are set at the correct settings.


I quite agree. in fact its as little as 20ma through the heart to kill some one.
However, Take into account ohms Law, and the higher the voltage for the same resistance (ie your body) the higher the current flow. Hence with 415V you will reach that lethal current more easily than with 240v.

My Point is simple. Think Safety, as there are a lot of pepole on here willing to have a go at all sorts of jobs. Sometimes a little knowlege is a dangerous thing. When dealing with 3 phase electricity, the result can sometimes be fatal.

Its no different than running your fuel lines alongside the wiring loom... We all know thats an instant SVA failure point. Namely its a simple safety issue thats not always blatently obvious to those with a little bit of knowlege, rather than the fully qualified knowlege.

I would feel it would be negligent of me NOT to point out these issues when I see them.
I for one would feel really badly if I saw something on here, and didnt comment. Then someone subsequently be seriously injured or died as a result of their lack of knowlege / experiece.

Its all about looking out for each other, and using our collective knowlege / experience.

I am happy to be shot down under those circumstances.
However, no one want to sustain an injury, let alone death.

MakeEverything - 13/12/09 at 10:51 AM

When i did my HV (11kV) training, we got onto the subject of Protection against Electric Shock (Part of the Regs), and they showed us photos of people that have been zapped by 132kV and 11kV.
The body (being 60%(?) water) is a great conductor, however, the joints are the highest point of resistance, and these photos showed where the joints had blown out like little resistors. Nasty!

Im sure that the official statistic is 250mA for a fatal shock...??


quote:
Originally posted by wilkingj
quote:
Originally posted by MakeEverything
quote:
Originally posted by wilkingj
240 volts Single phase, hurts when touched
415 Volts Three Phase will KILL.

If you are not a qualified electrician, then I would leave it to an expert.

Is your life worth £500 (for an electrician to do it properly)??



Actually, the voltage wont kill you, but the current will. It only takes 250mA to kill you if you get hit at the correct time. All to do with timing and your heart beat. 250mA is enough to send the heart out of sine, effectively causing a heart attack.

Just make sure the fuses are of the correct size for the cabling and the inverter. If the cable is rated at 63A (i forget my sizes currently) and is fed by a 100A fuse, the fault current (or max load current) could cause a fire or cable fault.

This exercise is called "Discrimination", and makes sure that all the fuses are the correct size and that breakers are set at the correct settings.


I quite agree. in fact its as little as 20ma through the heart to kill some one.
However, Take into account ohms Law, and the higher the voltage for the same resistance (ie your body) the higher the current flow. Hence with 415V you will reach that lethal current more easily than with 240v.

My Point is simple. Think Safety, as there are a lot of pepole on here willing to have a go at all sorts of jobs. Sometimes a little knowlege is a dangerous thing. When dealing with 3 phase electricity, the result can sometimes be fatal.

Its no different than running your fuel lines alongside the wiring loom... We all know thats an instant SVA failure point. Namely its a simple safety issue thats not always blatently obvious to those with a little bit of knowlege, rather than the fully qualified knowlege.

I would feel it would be negligent of me NOT to point out these issues when I see them.
I for one would feel really badly if I saw something on here, and didnt comment. Then someone subsequently be seriously injured or died as a result of their lack of knowlege / experiece.

Its all about looking out for each other, and using our collective knowlege / experience.

I am happy to be shot down under those circumstances.
However, no one want to sustain an injury, let alone death.