I'm getting a workshop built, and can make a choice to have 3 phase power connected. I'd like to buy some ex-factory machinery. Q: Is it worth the expense? Or, with electronic solutions to running 3 ph. machines from single phase power, is it not worthwhile?
You definately want 3 phase. Probably 220v. I wouldn't go with the
440v even though a lot of industrial equipment uses this. 220 is fine for most uses such as for welders and compressors. Plus you can run seperate 120v off each leg and get a larger load off the main line.
220v welders provide a much longer duty cycle and you can get a bigger air compressor also. The cost will be more because of the extra wiring and use of bigger wire but you will be glad as time goes by and you need more outlets.....and you will. Good luck
480/277V service is great for really big shops, but is to be avoided if you don't really have the need for it since the distribution panels and switchgear are significantly more expensive than the 120/240V single phase or 120/208V three phase versions.
Only if you get "Y" service which is 120/208V, not 220V. "Wild leg" Delta service will give you 240V on your three phase and 120V from only two of the three phase legs with the third leg being well above 120V relative to the neutral.
Yes, but 220V is available from single phase service as well. Three phase service will let you move up to the "next level" of welders and compressors like 500A+ welders and 10 HP+ compressors.
Three phase installations will use *smaller* wire than the equivalent single phase installation since a given load is distributed across 3 hot leads vs. 2 hot leads. Total wire used is of course more due to that third wire.
That depends on what the utility offers, how big your shop is and whether it's a business or personal shop. Three phase power will generally put you on commercial peak metered rates vs. kWh based residential rates. If your machines are all fairly small, there aren't too many and you aren't on commercial rates anyway, using VFDs or a rotary phase converter may be more cost effective. If you have anything over about 3HP VFDs used as phase converters become less cost effective. You basically have to make a spreadsheet listing everything you intent to put in the shop and then work up the initial and operating costs for the different options.
You don't give much detail about what you are doing. If for instance this is to be a private workshop on a residential property, the utility company may well be happy to provide a three phase (440???) service, which gets you power at industrial rates, and you can run your shop AND your house from it. You will have to buy a transformer for it to get the 110/220 household requirement, but in so doing you will then have a service suitable for all needs, eg single phase 110 &
220, and 3 phase 220 & 440. Good deal I think. Ask to speak with a technical representative at your utility. They can be very helpful.
The equipment is more expensive, but not solid gold expensive - 600V Class gear (277Y/480V) is roughly double the same stuff for 300V service. If you scrounge a little you can find it used, there are brokers who resell used gear, and they might have a 200A 277Y/480V service section for cheap because most of their sales would be of the bigger 400A and 600A sections.
Do ask the power company about the rates you'll pay for your various options, because they can have a profound effect on your decision that lasts for years - you only pay once for the gear and the install.
Commercial power rates are normally higher than residential, and it often has a "Time Of Use" factor - the KWH rate is cheap at night, roughly the same as residential rates in the mornings and evenings, but 10 AM or Noon to 5 PM "Peak Time" can be double or triple the residential rates - and that'll kill you...
They're trying to get heavy industries to start work earlier and shift their peak loads to the off-peak hours. Run the kiln and the heat-treat oven overnight, do the welding and machining from 4 AM to Noon. Leave the afternoon capacity available for air conditioners.
If you think you'll ever end up with any 480V equipment, get a
277V/480V Wye 4-wire system. You can easily run a transformer to drop the 480V down to whatever you want, but boosting from 208V or 240V up to 480V is a problem - you need double the amps and you run out of
240V panel feed real fast.
Having the neutral (4-wire Wye system) is important, because that gives you both the 480V and 277V options, and a lot of industrial high-bay lighting gear is 277V - one 20A circuit can light up a whole lot of space for cheap.
(But you want the fixtures to have individual fuses in them so they self-isolate, because with one lighting circuit having one bad ballast trip the breaker knocks out all the lights.)
3 phase is a slam dunk. There might be a minimun monthly cost from the power country but with your house and sho on 3 phase it will not affect your bill. Tuesday I am going to an auction where there will be lots of 3 phase equipment that will go for 20? on the dollar. If you need a 3 phase panels there are lots of them available on Ebay. For a home and/or home shop try to get 120/208 or 120/240 voltages. The remark about meeting with the technical rep from the power company is good. He can be valuable. Bob AZ