Pinging Bruce for Clarification

Lucky you. Not much need for 440 and the more expensive switchgear to go with it unless you have a really big installation.

Reply to
Pete C.
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Or you have a small shop operation and need to run specialized gear that only comes 480V 3-Ph. You can do a LOT more from a 480V 200A service than from a 240V 200A service.

You can boost 240V up to 480V with transformers, but you have to be careful to not max out the 240V service. The front office gets very annoyed when you blow the main and black out the whole building.

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Reply to
Bruce L. Bergman

If it's even remotely close to maxing out a 240V 200A 3ph service, it's a big installation, no mater how physically small it may be.

Reply to
Pete C.

Probably a regional thing. Shrug

Gunner

Reply to
Gunner

Chuckle..I did that yesterday.

Had 6 Moog Hydrapoints and 4 Okuma Twin Turrets running on a 200 amp.

Then I added a Okuma LS2200

Ooops

Well..he was hogging with a 1.25" drill bit. Shrug The hogging exceeded my very very thin margin..

Busted tools in just about every machine.

Gunner

Reply to
Gunner

Well...shrug..it is California. The 7th largest economy in the world.

You did say you live in the Rust Belt, right?

Gunner

Reply to
Gunner

I just have a Bridgeport mill clone and a lathe in my garage, pure hobby stuff. The machines have built in 440 volt switchgear.

David

Reply to
Mastic

That isn't switchgear, it's machine controls. The switchgear is the meter socket and distribution panel for the 440V delta service, both of which cost significantly more than the equivelents for 220V delta service, which those machines will happily run on. I'd never consider

440V service until I had at least 6 large CNC machines.
Reply to
Pete C.

No, more like you were betting on not all the machines running at the same time, let alone several of them running flat out and hogging at the same moment... And as you can see, that isn't a smart bet.

And the front office people probably weren't amused when their computers and AC went away either. Is this an industrial park, or can they bump the service up?

How many of those machines are dual 240/480V? You can get the new service in and change them over one at a time.

Sometimes you can cheat - if this is in an industrial park and the unit next door is only being used as a warehouse, they aren't using their full 200A service - you can install a sub-meter and get some more electricity from them.

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Reply to
Bruce L. Bergman

The customer was betting on it. I warned him many months ago. On the other hand..he pays very well and on time. Shrug.

I bumped it up from 200 amps total to 800 amps total, with multiple services. 4 shops in the complex, one with 600 amps total, 1 with 200 amps on the same meter main, and 2 with seperate 200 amp meter mains.

It took 3 months for the City and So Cal Edison to get their heads out of their asses on the new meter main..with another 2 weeks to convince the city inspector that 1992 Okumas never had, nor never will have UL listings.

Nope..only about 25% are dual voltage.

Already doing that with the 120 volt service...the bulding was built in 1959. Most of the shops had single 50 amp 120 volt service with a meter attached to the 6 breaker "main"

They hired an engineering company at the outset. Then they expected me to impliment the results.

Ive many compliments on the quality of workmanship, the way I designed everything for future expansion and so forth.

I dont get any brownie points for not getting 400 amps from a 200 amp service. Shrug

Its safe, its up to code, it looks good. But they simply dont have enough power in some places. And it will take an act of Crom to get anyone to make it so.

Then they stuck (2) I-R 15hp screw compressors and the dryers into the mix...cringe.

Gunner

Reply to
Gunner

Darn. Well, if you can get both flavors of power from Edison you can change over the ones that can take 480V, and that takes a lot of pressure off the 240V service. Will help the compressor problem.

Were they still on A-Base meters and fuses? ;-)

Hey, one place was trying to suck 200A through a 100A meter socket and Type RHW risers. They thought upgrading the panel to a 200A would solve everything... The rubber insulation was a bit crispy crackly after 50 years in that pipe.

Been there... Remember when houses had a 30A service because "we'd never need anything more than that..."? Then the single-family house standard went to the 70A "Crowfoot" panel. Then 100A. Then 125A. We held at 200 for a while, and now they skipped straight to 400A...

Progress marches on, and there's always another wonderful labor-saving (and power sucking) tool or appliance right around the corner.

Hey, that helps the power situation if they are put in constant-run mode and cycle on the unloaders, then there's only one start surge per shift. And it's those essentially locked-rotor start surges that kick the demand factor through the roof, and trip that Main Breaker that's teetering on the edge.

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Reply to
Bruce L. Bergman

An electronic soft start drive (or a VFD) could help here, right?

i
Reply to
Ignoramus2883

When you start a motor from a dead stop it draws the full rated locked rotor current for a few hundred milliseconds till it gets started rotating, and then the current ramps down over the next three to five seconds as the motor gets itself and the load moving and up to speed.

When you pay for commercial power with a demand factor, there's a demand meter that records the highest peak momentary amperage you draw. Looks like a big speedometer dial on the meter face, that's what they use the reset arm in the middle of the glass for... And they add a multiplication factor to your overall KWH billing rates based on the peak current you have drawn - this is to compensate the utility for supplying the oversized transformers needed to accommodate those current spikes, the transformers still draw current to energize the windings even if you only draw loads for a short period per day.

A motor drive can only help so much - it can regulate the LRA current to an extent, but it still takes a big grunt to get the load spinning. And the heating problem is still there.

Soft Starts are practical for motors that are expected to have short starts, like elevator pumps - but it's just as effective and less money to use a "Delta-Wye" reduced voltage starter on those motors. They get the motor spinning on Wye 277V and switch to Delta 480V running when up to roughly 80% speed.

Short cycling kills motors fast because they don't run long enough to cool off from the start surge heating, then they stop and the air cooling stops, then they are asked to start again with the windings still hot. Do that a few times, and the Magic Smoke (TM) escapes.

The trick on a constant-run compressor is there's only one start surge when you turn it on at the beginning of the day, usually with nothing else running. After that the compressor just opens the valves and spins idle, and the current draw drops off. (Not to zero, but the lack of start surges makes up for it.)

Reply to
Bruce L. Bergman

Bruce, forgive my ignorance, but let's say that a compressor has an unloader valve (even better, electrically controlled). Then the motor can be slowly ramped up to speed using a electronic drive, with the unloader engaging at the proper moment, right?

My compressor is single phase, but my Bridgeport is 3 phase, on a VFD, set to accelerate over 1 second when turned on. I am sure that it does not draw anywhere close to the LRA when accelerating that slowly.

What am I missing?

i
Reply to
Ignoramus2883

After a Computer crash and the demise of civilization, it was learned Gunner wrote on Mon, 10 Sep 2007 02:31:36

-0700 in rec.crafts.metalworking :

Sounds like he'll get to do it some more. Pay well, and on time. Good to have customers like that.

pyotr

-- pyotr filipivich "Quemadmoeum gladuis neminem occidit, occidentis telum est. " Lucius Annaeus Seneca, circa 45 AD (A sword is never a killer, it is a tool in the killer's hands.)

Reply to
pyotr filipivich

Sorry everyone.... for some unknown reason... I didn't get the original post or the original responses. I know they made it through, cause I saw them on the Google newsgroups at work (but I'm not set up to post there). I didn't get them at home, but I did get the posts under the header RE: Wondering how I can get Google to "send" the original headers and posts to my home computer.... any help here??? Thanks. Ken.

Reply to
Ken Sterling

If it has a centrifugal unloader that will not start pumping till the compressor comes up to full speed and the oil pressure comes up, like the higher end units from I-R and Quincy, yes the motor is essentially starting unloaded - well, except for getting the rotating mass of the motor and compressor moving.

You will still see a current spike at start, but not as big and it will ramp down faster because the motor isn't trying to produce work before getting up to speed. And for that, a start controller or VFD would be even easier on the motor and your power bill.

That your Bridgeport is manually started when you are standing right there, and if something goes seriously wrong you can kill the power.

Most compressors are designed to a price point (keep the mfg. costs as cheap as practical while meeting the specs for capacity and durability) so they won't spend for a soft-start. Unloaders cost more, so they are only built into the higher end units. And the compressor is expected to run unattended and start itself reliably every time air is called for, for decades, without anyone needing to run up and slap the power switch off if it stalls.

So the K.I.S.S. Principle says leave the electronics out if you don't really need them.

A VFD will work if you just set it at 60.0 Hz, but the whole idea behind it is Variable Frequency. The only reason I'd install one on a compressor is if you want to play around with Logic Controllers and adjusting the motor speed to the air consumption.

You can install one if you have one laying around and you want to (Play) experiment. But I still stand by "If it ain't broke..."

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Reply to
Bruce L. Bergman

To send the replies to your home computer, you could copy & paste the contents of the replies to a text document, while viewing the Google RCM group on any machine, then save the text file and attach it to an email, then send it to your email address and access it from home.

I just looked at some Goog RCM messages, and they have a Forward link at the bottom of each message, but it only works if you're signed in as a registered Goog member/subscriber.

This is yet another reason to have a couple of unimportant free Yahoo email addresses. Then you can join/subscribe to something useless like Goog Groups with a Yahoo email address as your username, and not have your ISP email address used at numerous places, attracting spam and nasties. Then, with a Goog username, you can forward those Goog Group RCM messages/replies from Goog Groups to your Yahoo email account (which you can access from anywhere), or to your other email account.

There are lots of worthwhile websites that offer access to good information, which require registration of users, so having some Yahoo email addresses will also likely come in handy later on.

WB ......... metalworking projects

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Reply to
Wild_Bill

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