Red diesel again

[john87]

Ok,

 

1, first off, No way will you drive a 30 hp anything from a single phase supply.. You might for a few seconds until the fuse went, as if you tried to drive a motor you would be pulling about 152 amps [once you allowed for PF and efficiency] and the voltage drop would be about 45 volts, so you would have anything from 208 volts to 171 volts left depending on the voltage of the incoming supply..

 

2, A split phase 460 volt supply is two phases 180 degrees apart with a centre tapped neutral. So, between each phase and neutral, you have 230 volts, and between the two phases you have 460 volts across two phases 180 degrees apart.

 

You say the inverter needs two 60 amp feeds, BUT what phase separation does it need [if any] ???

 

I would imagine that if it needs TWO feeds, then what is intended, is that it is powered between two phases of a three phase supply [lots of welders are like this] This would be two phases 120 degrees apart with a voltage of 400 between them. This is a mile away from 460 volts with 180 degrees of phase separation..

 

You might be able to adjust taps on the machinery to get it to run on 460 volts, but wht about the phase separation?? Think of it like this. Say on your car engine; What would happen if you  managed to advance one cylinder 30 degrees and retard the next one 30 degrees. How do you think it would run?? Be VERY careful here before spending a lot of money.. Make absolutely sure you KNOW what the makers requirements are..

 

3, People in pubs might tell you that a three phase supply cost fortunes, but this is generally bullshit from people that have never installed one. True, if you have to have a load of poles and a transformer installed, the cost will be very high.

If the DNO have to replace an existing transformer, the cost depends on how many consumers will benefit from the replacement. If it is just you, you bear the full cost, it it were 50 people, then you would pay 1/50 of the cost..

 

4, If there is already a three phase mains running past your property, AND if there is sufficient supply capacity that your installation will not affect other people's supply AND you are not going to install large motors or welders [in which case the DNO might decline to give you a supply at all] then the cost can be unbelievably cheap..

 

Have you asked the DNO for a price??

 

john..

[john87]

3 hours ago, difflock said:

How does your single Ph supply put enough juice forward to to drive a 30HP inverter?

I just bought a couple of 3Ph items and need to source a 3Ph supply, options being 3Ph mains(and still awaiting the no-doubt eye-watering NIE quote to install same), a diesel engined genny, or a PTO genny, or a rotary inverter limited to guessing 50A(since it is only a time limited 100A fuse) at 230V=11.5kW, and at single Ph electric prices, even that sounds eye-watering expensive to run!

 

I have TWO supplies to the same property, a single phase one and a three phase one. The cost per unit is exactly the same. Supplier is SSE..

 

john..

[dumper]

3 hours ago, john87 said:

I have TWO supplies to the same property, a single phase one and a three phase one. The cost per unit is exactly the same. Supplier is SSE..

 

john..

Change your supplier 

[john87]

55 minutes ago, dumper said:

Change your supplier 

Yes, i will have to look at options as they have just doubled the standing charge and the cost per unit has gone up an awful lot too..

 

john..

[Squaredy]

5 hours ago, john87 said:

No way will you drive a 30 hp anything from a single phase supply.

Well I hope it will.  The supplier of the inverter have confirmed that it will run off split phase which as you say is 180degrees of separation.  They have told me I need two 60A fuses and I have 80A fuses.

 

5 hours ago, john87 said:

People in pubs might tell you that a three phase supply cost fortunes

Sadly Western Power Distribution also told me it would cost fortunes.  And yes it would only be for me.

 

5 hours ago, john87 said:

If there is already a three phase mains running past your property,

I wish this were the case.  Nearest three phase is about a mile away.

 

But I appreciate your input, and yes of course I would prefer to have mains three phase, but unless there is a government sponsored scheme this is just too pricey.  The government should stop subsidising pollution and start subsidising attempts to reduce pollution (like replacing diesel gennies with mains power).

[openspaceman]

18 minutes ago, Squaredy said:

The supplier of the inverter have confirmed that it will run off split phase which as you say is 180degrees of separation. 

How on earth do they get to that?

 

Grid is 3 phases 120 degrees between each phase

[eggsarascal]

27 minutes ago, openspaceman said:

How on earth do they get to that?

 

Grid is 3 phases 120 degrees between each phase

You don't, unless I'm well mistaken. How 180 goes into 3 phases is beyond me.

[john87]

50 minutes ago, openspaceman said:

How on earth do they get to that?

 

Grid is 3 phases 120 degrees between each phase

Think of one of them yellow tool transformers. You have 240 into the primary side. The secondary winding has the earth connected to the centre of it, so that the output is two lines [one from each end of the secondary winding], with 110V between them, [180 degrees apart, [think sine wave] and between either end of the winding and the earth that is connected to the centre of the winding, naturally enough, you get 55v.

 

A split phase is the same but bigger. They run one single phase at 11,000v [from a three phase supply located elsewhere] into it and the output is 460V ac. Then all they have to do is to tap the centre of the secondary winding and earth "their" end and so you end up with two wires on the output with 460 between them [180 degrees apart, [think sine wave again]. You connect ONE of the wires to the neutral that is derived from the centre of the secondary and you get 230v.

 

The neutral of ALL supplies, single to your house or three phase is earthed at "their end" This is why you do not get a shock when you touch the neutal, because, as it rises to 230v so does the ground you are standing on, so there is no "potential difference" and so no current flows..

 

Now, you can have a broken neutral in the supply system. This is VERY dangerous, as, in a TNCS system the earth is connected to the neutral too. So, as it is no longer earthed at "their" end, it will rise in voltage just as the "live" wire does. This means that if you touch it now, and you are earthed, you WILL receive a shock..

 

This is the reason that you have "bonding" with all conductive bits in an installation, whether parts of the installation itself [like metal enclosures] or external earthed parts, [like a metallic gas or water pipe] all connected together, so the voltage rises in them all at the same time. Therefore, once again, you will not recieve a shock i you touch one while in contact with another..

 

Now, under these fault conditions, you hold a "class one" appliance [say a metal cased electric drill] and you step outside the "equipotential zone" [go outside] and step onto your lawn say, and you WILL get a shock.. This is why sockets that are used for things that will be taken outside, MUST be fed from an RCD which will cut off the supply as soon as you touch the earth [and therefore get your shock]

 

john..

Edited March 26, 2022 by john87

[topchippyles]

1 hour ago, Squaredy said:

Well I hope it will.  The supplier of the inverter have confirmed that it will run off split phase which as you say is 180degrees of separation.  They have told me I need two 60A fuses and I have 80A fuses.

 

Sadly Western Power Distribution also told me it would cost fortunes.  And yes it would only be for me.

 

I wish this were the case.  Nearest three phase is about a mile away.

 

But I appreciate your input, and yes of course I would prefer to have mains three phase, but unless there is a government sponsored scheme this is just too pricey.  The government should stop subsidising pollution and start subsidising attempts to reduce pollution (like replacing diesel gennies with mains power).

I have a good sparky just retired he does all 3 phase it you get stuck i can ask him if he can help gav. I have a 15HP rotary converter in my place that runs off a single phase works no problem what so ever. 

[Squaredy]

44 minutes ago, topchippyles said:

I have a good sparky just retired he does all 3 phase it you get stuck i can ask him if he can help gav. I have a 15HP rotary converter in my place that runs off a single phase works no problem what so ever. 

Thanks Les for the offer, and good to know you use a rotary inverter with no issues.