How to Check for a Missing Phase in 3-Phase Power When Motors Hum but Lights Work

Hello
I have an unusual problem, I suspect a puncture, but I don't know how to check it.
The symptoms are as follows.
-I checked with the bulb after the differential, all phases are lit and it's ok
- lighting is on, other devices (computer, kettle) are working
- the problem is with sewing machines (3-phase motors) do not work (hum) - this one is missing one phase, but some machines try to turn on the differential
- the drive to the gate (230V) does not work, the voltage is still available

the problem appeared when opening the gate, when it suddenly stood half open, I thought it was from the gate, first disconnected the power from the fuse in the box, but it did nothing, I removed the power supply directly in the drive, nothing changed either.

I don't know what to do, any tips, suggestions ??

greetings

Measure phase-to-phase voltages with a meter. Write what is your measurement result?

Hello. Old electricians use 2-bulb "test tubes" to measure the phase-to-phase [voltage]. Because maybe someone or something, e.g. wind, threw the lines on the overhead network. In this way, you can have 3 phases at home, except that one is missing> a blown fuse in the transformer station. And the third phase is the connection of the lines, so there are two.

And that's what he has. Master007 writes that the 3-phase motors are buzzing and the gate is not moving. He writes that the voltage to the gate is coming, but he probably checked the phase without checking the working zero. On the gate drive, he can easily check the voltage with a meter because there is the primary load of the power transformer Anyway, the voltage supply to the gate drive can be checked practically without any measurements, because there should be LED diodes on the electronics board that indicate the position of the gate's limit switches.

I am not talking about the lack of phase, but about repeating it in this way, with the lack of e.g. L2, there is e.g. L1 on this cable. And then we have:
L1, L1, L3 and N and L2 is missing.
There are enough "specs" who can bridge the wires on the power supply. And later they wonder ----- Why is the motor "humming", after all I checked with neon lights and all phases are. whether the bulb will recognize it. You need to check:
L1 - L2, L2 - L3. L1 - L3 [R - S, S - T, R - T] and must be 400V everywhere.

Of course you are right. I was recently to the "humming saw" where some specialty bridged two screws in the switchboard from the side of the 25A test fuse and the local electrician did not come up with it "because there are phases on the saw switch". But the power supply of the Master007 gate must be checked. Bronek 22 is also right that the meter must be able to use, but this is not a "new invention" but a basic electrician's measuring instrument. , because uncertain zero in, for example, a single-family house is an avalanche of damage to electronic equipment (instead of zero, the second phase appears unexpectedly in the socket).

What about it all master007 . Have you measured the interfacial tensions ??

Hello
The topic is worth remembering by many electricians. The meter is a meter, but an old tester with a load, such as a light bulb, cannot be deceived, of course, the measurement between phases.
I think that every experienced electrician has survived such a case.
George

Hello. To a telephone question, such as "I have all the phases and the engine hums", my first query is - "what did you check".
If the answer is - neon, then for me it is a signal that it is a waste of time to translate. Better to go and check it yourself, and as it is, it was discussed here.
Greetings.

Well, gentlemen, what is there to discuss? The neon lamp is only an indicator and is not suitable for any diagnosis.
More than once I went to the washing machine which, according to The client does not show any signs of life and the voltage in the socket is in place, it turned out that he was checking it with a neon lamp.
In fact, a burned out wire in the socket or a blown fuse.