[SOLVED] Three phase wiring question

Bernie would demand a fixed minimum income for electricians so that they'd have more free time to bone up on the latest developments in 3 phase wiring.

Hillary would ask her donors for enough money to fund 6 national polls to see what she should do.

The Donald would blame the problem on China and Mexico and say that he knows the secret and if he was in charge all wiring colors would be very very very correct and the most uniform in the history of electricity. If pressed sufficiently he would produce a rummy former electrician who would recommend a three black wire national standard.

We here at the Oregon occupation think you should wait until dark, cut the locks at a better location and move in there.

O.R.E.O.s

PS Why do you need a switch anyway? Save the money and join the revolution. Sooner or later we'll take over a VFD distributor. Then all you'd have to do is read a manual and press some buttons to change direction.

You want a phase rotation tester see

. I've never used one but have spoken to electricians that have, a fairly common piece of kit in the toolbox if you work with 3 phase machinery regurlarly.

eir hands in this place. They called me today with a problem:

It has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

prevent it from switching while it's running. Well, yes I could do that, b ut why don't they just rewire the outlets so they're all the same?

sure they do it right.

tor and checking for correct rotation, but surely there's a better way? Wha t if this was a big piece of equipment, or something that would do damage i f the motor turned the wrong way?

f them when I pull that out), but is there an even better way? How do "real " electricians identify the phase connections when they can't count on the wire colors?

There will be one in my toolbox (well, tool bag, actually) tomorrow.

ir hands in this place.

It has a 3-phase

been swapping wires inside the motor junction box.

prevent it from switching

rewire the outlets so they're all the same?

ure they do it right.

or and checking for correct rotation,

nt, or something that would do damage

them when I pull that out),

e phase connections when they can't count on the wire colors?

If we could just take over the national power grid, I could use an app on m y phone to change the rotation on every three-phase motor in the country. T hat would be very cool.

I'd come to Oregon to join the mob^H^H^Hrevolution, but I'm busy standing g uard here in New Jersey. If Christie gets any closer to be taken seriously, we plan to blockade all of the ball fields where his kids play so he won't be able to land his helicopter. Can you run a campaign from a helicopter t hat can't land? Surely there are papers that must be signed.

Hopefully Trump will win the nomination. Which would free up Christie to join the revolution. Lots of room for his chopper here. I bet he knows how to block the bridge to Oregon.

O.R.E.O.s

PS Plus, if we run out of food at the compound, Christie's thighs alone would last us a week.

They sell phase rotation detectors, like this one:

I'm doing some work in an older factory - MANY electricians have had their hands in this place. They called me today with a problem:

Well, if you know which outlets run it backwards it should be pretty simple. Just switch any two wires. If you want a "simple as a sack of rocks" test, just grab a small 3 phase motor and lable the wires - use it as a test motor to determine phase rotation.

This was a somewhat new plastic injection machine. I say somewhat new because it was rolled over onto its side when the riggers were bringing it in. Customer was none to happy with that. So the machine already had a "story"...

Our obvious concern was that the machine had a good sized hydraulic pump on it, run by a three-phase motor. Hydraulic pumps don't always like to be spun in the opposite direction... We got away with it, at least long enough to determine direction of rotation. Even if we had had a direction determining meter/device I don't know how we would have correlated it with the machine wiring at the time...

I remember whole shops getting thrown out of whack, rotation gone backwards after the power company had done work somewhere on the incoming power lines down the street. Oops!

ir hands in this place. They called me today with a problem:

It has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

prevent it from switching while it's running. Well, yes I could do that, bu t why don't they just rewire the outlets so they're all the same?

ure they do it right.

or and checking for correct rotation, but surely there's a better way? What if this was a big piece of equipment, or something that would do damage if the motor turned the wrong way?

them when I pull that out), but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the w ire colors?

Unfortunately, I don't know which outlets are forwards and which are backwa rds. And while you'd think the customer would have kept track...Dumber than a sack of hammers comes to mind.

There are actually meters for this that have a tiny motor in them to displa y the direction. I like that, but I've already received the LED thing from Amazon.

Such things should be protected by "three phase rotation relays".

i

Tell the Germans back in the 70's. Maybe they weren't invented yet.

We had the electrician (we is loose - county school I live in county) wire up a very large and powerful CNC umpteen axis machine and blew up the campus transformer! That is a big transformer for a college.

Took two days to get one installed. Department head was axed. Had to do it to someone. (He was a friend).

A meter would have detected the shorting neutral/gnd to a hot and a hot to a neutral ground.

Lots of stuff had to be replaced on the new monster mill. The regional companies that supported the class - feeding them programmers and users They stepped up and paid for the burnt motors and such.

The electrician for the school, a Master, blew it and others caught it.

I think to boot it, the voltage was from the wrong panel and was the wrong voltage as well.

I worked in a R&D lab with large machines and we had 50, 60 and 400 Hz power buses. The 50 and 400 was generated on site. You can bet we had stuff labled and checked it when a bus wasn't being used.

Mart> >> I had students with a Can manufacturing company that got a big

r hands in this place. They called me today with a problem:

t has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, s o they have been swapping wires inside the motor junction box.

revent it from switching while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

So, I was at the factory today to fix something completely unrelated, but I threw the phase detector in my toolbag just for the hell of it. Having tak en care of today's issues, I spent some time with the maintenance mechanic talking about their three-phase issues. It turns out (as it usually does) t o be more complicated than originally stated:

There are about a dozen different machines that plug into a dozen or so out lets, in various combinations. I tested four outlets and found two wired cl ockwise and two wired counterclockwise.

The plan is to go to all the department heads and compile a list of all the equipment that plugs into three-phase power. We will check each outlet and modify as necessary to get them all running clockwise. Then we'll modify t he wiring in the machines as necessary to get them all to run correctly on clockwise power.

This will all end up being a couple of solid days of work, but when it's do ne, it will be done. Forever. Until someone changes something...

But it was good today to see that the little

Good to hear. After reading a few reviews for some of the less expensive testers via Amazon people were having trouble with them. Or they didn't know how to use them. One can never be sure ;-)

Thanks for the followup!

With the current prices, functions/abilities they have, I would get one if I was still doing that kind of work.

Yeah, it's nothing special, but the instructions are in Cinglish, so I can see how people would get confused.

The unit has five LEDs - L1, L2, L3, CW, CCW. It also has three test leads with screw-on alligator clips. All I did was connect the three leads to the appropriate terminals on a mating plug. If you get all three L LEDs, you h ave all the phases. One of the CW or CCW will light, telling you which dire ction you're wired.

There's also an anemic buzzer in there, that pulses for CW and is steady fo r CCW, but I could barely hear it in any of the four rooms I tested in.

There are better, more expensive testers, but this will certainly do what I need for this job.

I mentioned all this to my brother who is an electronics tech at a large US PS facility. He told me about the time they lost a phase and had to replace a LOT of contactor contacts and other stuff. A lot of noise and smoke.

He also said that even though they are meticulous about making sure that ev erything is wired correctly, and there's paperwork to prove it, they still have an only slightly better than 50/50 chance of being wrong when they ins tall a new machine.

I got to replace something like a 5hp 3-phase motor for an air compressor once at the County Road Commission. They lost a phase and the compressor tried to run on the remaining two. Rather than pull the disconnect for it the guys in the shop just watched it kill itself over a period of time...

Really hard place for an outside tech to work. End up with a bloody tongue before long...