determine legs in 3 phase

Most of the time I did the same. However, on two large r&d projects where we had 15-20 motors, we did use a phase meter. I don't remember what type. On those projects, I did the control programming and programmed all the vfd's. Since I preferred an active tune, I had them all uncoupled initially anyway.

Most of my pumps were positive displacement, but I've seen centrifugals with threaded spindles where getting the rotation wrong would spin the impeller off, damaging the housing, impeller, and spindle in the process. Even before vfd's, we started those up uncoupled first.

Pete Keillor

Reply to
Pete Keillor
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I was taught to label every wire on both ends to match the schematic. The incoming phases were 1L1, 1L2, 1L3 and they stepped to 2L1, 3L1 etc as they passed through breakers and contactors.

In prototype electric vehicles where text is more useful than numbers we printed the wire labels on white heatshrink.

For home projects I write on the heatshrink with a fine Sharpie and color code with nail polish.

-jsw

Reply to
Jim Wilkins

determine legs in 3 phase

On Friday, January 16, 2015 at 12:59:49 PM UTC-5, Cydrome Leader wrote in rec.crafts.metalworking:

In testing you normally use black, red and blue for live low voltage and brown, orange and yellow for high voltage connections.

For low voltage, black fingernail polish or tape for 'A' connections, red for 'B' and blue for 'C'. Use green for Ground-only connections and white or Grey for neutral connections.

For high voltage, brown fingernail polish or tape for 'A' connections, orange for 'B' and yellow for 'C'. Green is still used for Ground-only connections and white or Grey for neutral connections.

Reply to
mogulah

Sure. And just in case you've scared the fire department, maybe here's how to tidy things up to standard per code:

"The high leg service conductor of a 4-wire, 3-phase, delta connected servi ce must be permanently marked orange or identified by other effective means [NEC Article 230-56], and must terminate according to the following: meter termination: ANSI requires termination on the C phase; panelboard and swit chboard termination on the B or center phase [NEC Article 384-3(f)]. "

Reply to
walter_evening

They should have. I had a call for a dead scoreboard at a high school. It was a bad breaker, in a huge panel near the gym. It was so messy that one of the phases was hidden, and against the inside of the lip that held the cover. I set the cover back in place, and before I could tighten the dogs, I tripped a 400A three phase breaker in the main electrical room. That shut down 1/3 of the school. SOmeone had done it before, and didn't bother to bend it back out of the way, or cover the damage. They just wiggled the dogs on that side under the wire. I reported the repair, and problem to the head of their maintenance department, and was told about all the other shoddy work they had found on the 20 year old building. It sounded like some disgruntled idiot was out to kill someone.

Reply to
Michael A. Terrell

Is this neon tester something can be popped open and photographed? Somebody mentioned the term "phase rotation" and bam, I see the $15 testers on ebay and amazon now.

Not sure I'd trust those things to not explode with all the leads vaporizing at the same time. I just imagine wires and floor sweeping componensts twisted together inside a plastic case.

It does sound like everybody does just test things first and a small motor or fan might be the best way to do this, unless I make a tester for the hell of it. Playing with neon indicator lamps again might be fun.

Reply to
Cydrome Leader

Here's how to build a very simple one:

Good Luck, DoN.

Reply to
DoN. Nichols

Neon bulbs draw milliamps or they explode. The reactance of the parts limit the current. The insulation is important and the 'voltage' range that it works in is important. e.g. 120v or more and less than 440 or some such. Insulation of the leads and circuit as well as the parts require the high voltage spec while the low end is the Neon (63V) and other components dropping voltage.

Martin

Martin

Reply to
Martin Eastburn

I've never had to worry about such. My bud had a device that would place an RF signal on a wire and he could then trace it through the shop. It sure came in handy tracking down a mysterious ground loop or whatever you call it.

Reply to
Tom Gardner

That 'schematic' shows lamps, but the thing WILL blow up if you put a simple neon lamp in those positions: you need to use neon lamps plus current-limit resistors, and the circuit works because of the high strike voltage and lower sustain voltage of the neon lamps (can't do this with LEDs!). It looks like the first lamp to fire causes the capacitor offset voltage to shift, so the second lamp is dimmer. It isn't polarity-sensitive, the lamps will flash twice per cycle.

Reply to
whit3rd

Actually, that circuit is for INCANDESCENT lamps.

Reply to
Bob Engelhardt

Yep, I missed that. It relies on lamp resistance value as well as incandescence, which is an odd combination. Hot lamps are much higher resistance than cold ones. I'd guess a neon-plus-resistor would allow more voltage range, and you could keep a single capacitor value

Reply to
whit3rd

Not at all sure that the lamps are neon lamps. I think small incandescent lamps rated for the voltage of the supply being tested.

It is dependent on the impedance of the capacitor and the lamp acting as a voltage divider, and the second lamp sees less voltage because of the phase shift.

There are formulas at the end for selecting the proper values of resistors (if any) and capacitors to go with the lamps and the power lone voltage and frequency.

Note that common pilot light Neons have the current limiting resistor built into the housing for common mains voltages.

Enjoy, DoN.

Reply to
DoN. Nichols

The doc lists incandescent - 220v lamps. Baring them, put two 120v lamps in series and it should work just the same. Light is spread over four bulbs...

Martin

Reply to
Martin Eastburn

The issue with neon in this example is voltage drop. Xc of the capacitor is vs the resistance of the lamp.

A neon is a switch. It is a voltage regulator. It fires at a defined voltage and turns off at another. One can't see a dim one unless you limit the current and keep the voltage constant. An FET would have to be used....

Use lamps. Not neon glow tubes.

Martin

Reply to
Martin Eastburn

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