3 Phase & Converter question

[dagoof]

I'm looking to get a 3 phase machine into my residential garage - problem is the garage is about 30ft from the street. The machine's power requirements state "400 V 3P+N+T, 50/60Hz, 18 kW" and I'm just looking into whether a phase converter will be possible.

Any reasonably priced converters I've seen list around 3hp and 2kw - but I take it I'd require a 25hp beast if the machine is 18kW as listed above? A genny isn't possible.

 

[JohnW2]

... and yet another duplicate eradicated!

 

[JohnW2]

Duplicate eradicated!

 

[JohnW2]

I'm looking to get a 3 phase machine into my residential garage - problem is the garage is about 30ft from the street. The machine's power requirements state "400 V 3P+N+T, 50/60Hz, 18 kW" and I'm just looking into whether a phase converter will be possible. Any reasonably priced converters I've seen list around 3hp and 2kw - but I take it I'd require a 25hp beast if the machine is 18kW as listed above? A genny isn't possible.

You're presumably going to need to get a new supply for that, separate from your house supply (18kW is nearly 80A at 230V single phase) - so you might as well look into getting a 3-phase supply. Sounds expensive! Out of interest, what sort of machine is this power-guzzler?!

Kind Regards, John

 

[JohnW2]

Another duplicate eradicated - what is going on?!!

 

[ericmark]

As John says a little big for single phase. If you have miss-read and it was 1.8kW then it would be a different story. Smaller machines often have motors which at 400v Star wound and 230v Delta wound. By swapping links in the motor to delta a relativity cheap inverter can be used which will also soft start the motor.

However the larger motors are wound 400v Delta and the star voltage is much higher to allow star delta starting. An inverter to run these would be huge and very expensive.

To turn the whole supply to three phase is not really an option as the in-rush would be so large. Only the motor would have three phase. This may mean control transformers will also need changing.

Cost is very much related to demand and because of the speed control with inverters they are quite common for small motors but for large motors factories will not use 230v inverters so the cost is very high.

 

[Spark123]

I thought the idea of star-delta starting was to have the lower voltage (230v) across each coil in the motor (when in star) to reduce start up current? Then flip over to delta after it has ramped up therefore 400v across each coil?

Not that this helps the O/P, if it is indeed a 18kw then he'll need his own supply from the electric board as a converter will pull 78A on FLC. Better with a 3 phase supply. What is the machine anyway?

 

[ericmark]

I thought the idea of star-delta starting was to have the lower voltage (230v) across each coil in the motor (when in star) to reduce start up current? Then flip over to delta after it has ramped up therefore 400v across each coil?

In Star you have a 600v winding feed with 400v approx so it does not pull as much current in Delta you have a 400v winding fed with correct voltage of 400v so has full power.

Consider 3 x 400v bulbs wired star and delta. In delta will have correct voltage in star only 230v to each bulb so will be dim.

As you say if he has quoted power requirements correct highly unlikely he can use single phase. It would require an inverter as without it the inrush would be far too high. Which in turn means rest of machine still would be feed with 230v and likely the control circuit will have a 400v to control voltage not 230v to control voltage so that transformer would also require changing.

The old Ward Leonard Drive System may be an option where the rotating mass of the rotary rather than static inverter will absorb the inrush better but the cost would be huge. That was the idea with the old lincoln bullet welder but if really it needs that sort of power then I would be looking at either a generator or direct drive from a petrol or other engine. Well I say direct really mean belt drive to smooth it a little.

Other methods include hydraulic linking. SLD pumps had some submersible pumps with hydraulic link to main engine with a swash plate pump so it also had speed control.

 

[securespark]

Another duplicate eradicated - what is going on?!!

I've suffered this before. If your mouse is dodgy-wodgy, it can post several replies with "one" click.

Try swapping your mouse.

 

[dagoof]

Thanks for the replies - it is indeed 18kW, no mistake! It's a piece of printing equipment but uses heat in addition to motors.

As mentioned, the garage is a fair distance from the street so I think it'd be prohibitively expensive. The garage does back onto a lane but I'm guessing there wouldn't be supply there.

 

[dagoof]

Was just looking at main fuse box and coming off the main cable there's a black box labelled 415v/100a (attached). Could we have 3phase here already?

View media item 50354

 

[Spark123]

No, that is a single phase cutout. If it were three phase there would be three fuses.
That back box next to it looks dodgy too

 

[JohnW2]

Thanks for the replies - it is indeed 18kW, no mistake! It's a piece of printing equipment but uses heat in addition to motors. .... As mentioned, the garage is a fair distance from the street so I think it'd be prohibitively expensive. The garage does back onto a lane but I'm guessing there wouldn't be supply there.

As I and others have said, if it's really 18kW, then you are almost certainly going to need a new supply (I would have though 3-phase) from the electricity company. That will, indeed, be very expensive, but I don't think the distance from the street (within reason) is going to be major part of the equation - it would be very expensive even if very close to the street!

You would also have somewhat of a heat problem in the garage - most of that 18kW will end up as heat - and that's an awful lot of heat in a small space!

Kind Regards, John

 

[JohnW2]

Another duplicate eradicated - what is going on?!!

I've suffered this before. If your mouse is dodgy-wodgy, it can post several replies with "one" click. Try swapping your mouse.

On this occasion, I doubt that was the explanation - if you look, you'll see that the four copies of the message which got posted were timestamped with slighly different times (9:16, 9:17, 9:18 & 9:20) - mouse 'bounce' could not possibly explain that! The website is fairly 'flakey' at the best of times, and I suspect therein probably lies the explanation on this occasion!

Kind Regards, John.

 

[dagoof]

Thanks John/Sparky - it's more of an outbuilding than garage though!
The current owner of the machine said he had run it off a £2.5k phase converter but even at that, it's not really an option unfortunately.