Three phase motor onto inverter

[Trevanion]

I was quoted £8000 per pole for a three-phase line at 5 poles over a quarter-mile.

It's ridiculous, there should be some kind of grant in place for businesses to install three-phase so everyone isn't burning diesel all the time.

On a side note, how come Tesla can get 750HP out of a battery charged overnight and I can't get a battery to power the workshop powering 8hp machines at most that just trickle charges overnight?

 

[Jackbequick]

Perhaps I should mention that (resultantt) orque is directly proportional to square of applied voltage but there are other factors as well which will have received (if a good machine) consideration and which may interest you Torque Of Three-Phase Induction Motor Explained (a random grab) amongst the advertisements this has some perhaps useful slip and other information What is starting torque in three phase induction motor? - Quora and a general treatise with many good revelations for the everyday person I (as an electrical engineer) thought might interest you. These might raise your interest also. Objective Questions on Torque Equation of Three Phase Induction Motor | Electrical Study App by SARU TECH. That's all from me.

 

[AJB Temple]

I have a pole with transformer on the perimeter of our garden (inside our land but outside the garden fence) which carries 3 phase to an industrial unit about a mile away across fields. I am in the process of enquiring about 3 phase to my planned new (totally unbuilt) workshop, which would be 20 metres from the pole. I have been told by a surveyor to expect £5k connected and a wait of 9 months. It's ridiculous.

3 phase is often available in commercial parts of London. Frequently used by restaurants.

 

[Jackbequick]

Those things in my reply in red were URL's they still may be.

Pete thanks for the head's up. That's a massive current availability on single phase...I guess that's the way they do it. There is a proviso do you have individual transformers? It sounds like it may be so at those costs Trevanion mentioned. The French have a somewhat similar rental situation and the wire to my place in France looks like a piece of fishing line. I presume it glows at night.

Trevanion....I agree but "take heart"....I was quoted at my country land $60,000 in Australia to have a local install 3 poles etc and supply-fit an 11kV to 240V transformer. Distance about 60 metres. Having worked on supply towers etc I could (personally) supply fit and fit out all poles cross arms and the HV as far as hook-up and as well the low voltage board but I don't have that licence....and in fact am too old for that sort of high risk work.

At that point for a tenth of the cost or less I could buy a mobile 3 phase diesel generator or perhaps go battery-bank solar.

Domestic in Australia is generally at 80 amps and over that it's probably cheaper to add a phase. Earlier-on most of the older houses I attended used two phases, individually metered ...one for appliances and one for the (typically 'off-peak' HWS. 3 phases generally ran down each street..hookup was pretty simple with overheads. Going single to poly-phase today we change the meter also to 3 phase. Logically the electrician might re-balance the load connections at the board.The elephant in the room today is the effort made to go underground directly to meter box rather than overhead to "point of attachment".

If the miserable electrical design has conduit spec'd for single phase and inadequate for the extra two wires ...well actually enough diameter to safely pull through the extra wires... it can be tricky. I always put to the client, with explanation the option of pulling in 4 core 16mm squared csa whether in conduit or "buried directly" and leaving it terminated . I suppose 60% of individual domestics thought it a good idea, ....apartments rarely but their service ducts ran polyphase anyway so access to it was pretty simple.

 

[Jackbequick]

I have a pole with transformer on the perimeter of our garden (inside our land but outside the garden fence) which carries 3 phase to an industrial unit about a mile away across fields. I am in the process of enquiring about 3 phase to my planned new (totally unbuilt) workshop, which would be 20 metres from the pole. I have been told by a surveyor to expect £5k connected and a wait of 9 months. It's ridiculous.

3 phase is often available in commercial parts of London. Frequently used by restaurants.

Thanks for the info....I'd be getting some quotes from local sparkies.... You may find one or two who can do a lot better. As well (an was he a cadastral surveyor (no idea) or or a quantity surveyor (much better idea))what he may be including is some 'share' in the purchase cost of the transformer itself....making a donation to the present end-user. Alongside the industrial variations your demand variations may be pretty insignificant to the load balancing. Five thousand quid is a lot in conversion to our dollars but I'd seriously consider it when to you it's about the same as $5k...You have maybe the option of solar and battery to supply 3 phases or at least speak with a sparkie about running the three phases now to the right place for perhaps a future connection when you either get a cheaper price or can cop it on the chin. When getting prices now I'd be asking each one to separately price a 3 phase hook up...My Regards

 

[Inspector]

"There is a proviso do you have individual transformers?"

To be honest I have no idea. I'm on 9 acres and on the property line is a big green box that has whatever is needed. It is a couple, three hundred feet away from the house and may have a transformer in it or maybe just the connection points to the house. With the house on natural gas for forced air, hot water and cooking there isn't really a need for that much power but some people have electric heat, stove, water, air conditioning etc and use it so the utility provides it. I have a 100 amp sub-panel in the garage to service it and the shop above. Lots of 110 for lights and plugs and 220 circuits 15, 20 30 and a couple 40 amp circuits for machines. I'll be using a VFD to run the 3ph delta motor on the DC to vary the airflow as needed. See got back to VFD's ) Was cheaper to run a sub than to run everything to the main panel.

Pete

 

[Jackbequick]

HI Pete of course I'm not there but the big green box if like 2m x 1,5M x1,5 m sort of arrangement might be what we electricians colloquially call in Australia 'a kiosk'. It's likely to be something like 11 kV to 415 V transformer possibly only feeding some local pole-tops. My property mentioned is over 700 acres and about 2kM square . Mains is extremely expensive to feed that lot!!

Ok on the rest...You could probably run a 3 phase 'tractor-pack' for short jobs ...if you have a tractor. Sometimes that sort of gear turns up cheaply. Bear in mind when running gear that that every extra coulomb causes an increase in voltage drop. As the voltage drops to motors, for example, the current increases, slip increases, torque decreases. Leave it there... My regards

 

[Inspector]

I’m not so sure the voltage is that high but electrons and I have just a passing acquaintance anyway. There is a easement from the highway along the edge of the property to the box. It is about a one metre cube and there is one between every pair of properties. A smaller telephone box beside it. Guess they share the same trench, all the power is underground. We’re in what is called a rural subdivision with properties an average of 5 acres.