Power Issue with my Machine Shop

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- Carbonite
  
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posted
16 years ago

Mon, Nov 13, 2006 3:59 PM

I started a small shop in a 900 sf building I have on my property in
the country. Before I moved in the prior owner had a woodshop, the
building has its own power and gas. 11 months ago I bought a
Bridgeport Milling machine with a phase converter. The power off the
transformer is shared with 2 other neighbors. Everytime I turn on my
mill there is sudden dimming of the lights and it did it with the
neighbors lights in there house too. I called my power company and
they came out and changed the transformer from 5 kva to 25 kva. I
still see little bit of a power drop in the neighbors lights, I work at
night and now that it is getting darker out I can see the issue. Now
that I am getting busier now and getting a lathe in 2 weeks I am
wondering if I can get my power on my own transformer, do you think it
will be expensive or should pay an electrician to upgrade my power to
200 amp service which would make the power company come out and put in
even a bigger transformer? I have a 100 amp service and all I have is
a mill and then I am getting a lathe that runs on 220 single phase.

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- Bob AZ
  
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posted
16 years ago

Mon, Nov 13, 2006 4:29 PM

I have a 100 amp service and all I have is

Get things setup on real 3 phase and move on.
Bob AZ

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- Grant Erwin
  
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posted
16 years ago

Mon, Nov 13, 2006 4:32 PM

When you turn on an electric motor, its starting current is momentarily larger than its running current, even loaded. All wire has resistance. The large current running through the wire resistance causes a momentary droop of voltage, which is what causes the lights to dim briefly.
You could go talk to your neighbors and explain to them that you're just turning on an electric motor. If your relationship with them is good, and if you help them fix things from time to time, maybe you can solve this problem politically; i.e. just by talking.
You could also maybe switch to a rotary converter with power factor correction capacitors installed. You can't do much about starting current in your mill's motor, but at least this way you can reduce the reactive current in the line, all of which contributes to the perceived voltage drop.
GWE

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- Trevor Jones
  
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posted
16 years ago

Mon, Nov 13, 2006 4:34 PM

So call the power company and ask!
Since you have not supplied a location, or the name of the power company, there is little chance of getting usefull information from any other source.
You may get lucky and the Power Co will upgrade your supply for no cost, as it appears they have already done with the transformer, or they may tell you that you are getting as good as the supply line is capable of, in which case I would be looking at three phase motors, Variable Frequency Drives (aka VFD's), and programming in a soft start , so that the surge does not take down the neighbors power.
Cheers Trevor Jones

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- Ignoramus8450
  
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posted
16 years ago

Mon, Nov 13, 2006 4:54 PM

5 kVa service??? That you share with your neighbors???????????

I would just get a variable frequency drive. It is much nicer in regards to starting and running those motors, as far as starting surges are concerned.
i

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- Bob Engelhardt
  
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posted
16 years ago

Mon, Nov 13, 2006 5:04 PM

The neighbors lights dimming is the power company's problem, not yours. If a 25kva transformer isn't enough that's their determination and their's to fix.
If you're going to be working alone (no employees) you will only have one machine going at a time and 100 amp service should handle that easily. However if the panel needs to be replaced anyhow (e.g., if it has fuses), 200amp would do. If you're talking about a mini factory with multiple CNC machines running simultaneously, that's a different story.
Bob

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- Randal O'Brian
  
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posted
16 years ago

Mon, Nov 13, 2006 5:12 PM

VFD's would eliminate the starting surge plus give you convenient (and superior) speed control for both the lathe and mill. You already have a 3-ph. motor on the mill, so VFD addition would be easy. The lathe would need a 3-ph motor also.
VFD's are so cheap that phase converters are no longer a viable option when you take into account the additional benefits of electronic speed control, soft starting, etc.
Randy

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- Dave Lyon
  
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posted
16 years ago

Mon, Nov 13, 2006 5:50 PM

You've never lived in the country have you?
Real 3 phase power could be many miles from his house.

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- Pete C.
  
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posted
16 years ago

Mon, Nov 13, 2006 7:14 PM

In all probability that was supposed to be 15 kva. Remember also that these utility grade transformers are rated to handle a 100% overload for 24 hours without damage.
If the OP is really out in the country the problem may be in the primary distribution lines out to his area and not in the local transformer. Indeed if a Bridgeport of what, 2 hp starting up is causing a noticeable dip after the transformer was upgraded to 25 kva this is likely the case.
The utility isn't likely going to replace the miles of primary until they are convinced it is old enough that's it's become more costly to repair than replace, or some big customer comes into the area like a big commercial building or a big housing developer.
Pete C.

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- gcc
  
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posted
16 years ago

Mon, Nov 13, 2006 8:00 PM

I'm not an expert or anything but it should be pretty easy to rig up a UPS unit to feed enough power to get past the initial current ramp on those motors- I can't vouch for your area but I know around here almost every junkyard has several large UPSs that you can buy by the pound. The trick will be matching your discharge curve to that initial spike- you'd need a much larger unit than rated for those motors because they draw so much current cold. Beyond that though it shouldn't be a problem- just make sure that you're primed before you turn the whole setup on.

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- Ignoramus8450
  
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posted
16 years ago

Mon, Nov 13, 2006 8:04 PM

My 10 HP idler motor draws about 120 amps of 240v at startup. That adds to about 28 kVa. Very serious size for a UPS, it would weigh about a ton. It would also have enough electronics to salvage to afford to buy a small VFD for the bridgeport mill.
i

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- Pete C.
  
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posted
16 years ago

Mon, Nov 13, 2006 8:06 PM

Much simpler to spend the $200-$300 on a good VFD that will allow you to soft start your three phase motor.
Pete C.

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- gcc
  
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posted
16 years ago

Mon, Nov 13, 2006 8:19 PM

simpler, just not as MacGuyverly. Or cheap, if you can find junked UPSs. I think this may be why I live alone, however ;).

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- Pete C.
  
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posted
16 years ago

Mon, Nov 13, 2006 8:42 PM

Right, you have to get a big (free) three phase online type UPS and modify it to provide you with "real" three phase power for the shop complete with starting surges, while drawing a nice constant load of single phase from the utility and even keeping you from wrecking parts you're working on when the utility power goes out.
Pete C.

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- Pete C.
  
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posted
16 years ago

Mon, Nov 13, 2006 8:46 PM

Yep. My short furry wife (cat) never gives me any crap about buying tools.
Pete C.

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- Ignoramus8450
  
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posted
16 years ago

Mon, Nov 13, 2006 8:47 PM

Yep, good point about those giant UPSes being 3 phase.
i

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- gcc
  
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posted
16 years ago

Mon, Nov 13, 2006 9:01 PM

Yeah, to be honest I forgot about that- used to dealing with UPSs for computers. I'm still sure you could rig it but its seeming less and less worth it.

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- Bob AZ
  
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posted
16 years ago

Mon, Nov 13, 2006 9:36 PM

Yes I have. But the OP said they replaced the transformer with a 25KVA. That says 3 phase is distributed nearby to me.
Bob AZ

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- Pete C.
  
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posted
16 years ago

Mon, Nov 13, 2006 11:25 PM

Not sure where you come up with that, perhaps something unique to the utility in your area. I've seen numerous 25kva transformers far from any three phase feeders and that's in two different states.
Pete C.

posted
16 years ago

Tue, Nov 14, 2006 12:16 AM

PV: Ahm takin some shit to the dump. Wife: Come back w/ *anything* FROM the dump, and yer dead meat. PV: Yes, dear. I make sure I come back after she's left for work. :) :) Let's see-- junk--wife--junk--wife--hmmmm, well, wife *does* cook good.....