Discuss Volt meter reading 760volts in 3phase dol starter overloads in the Industrial Electricians' Talk area at ElectriciansForums.net
I have had uk power networks out and they have checked their supply and all is fine. I can only seem to find this fault on these contactors because they are the only ones which have a neutral in the system for the pilot light. The main lighting and single phase sockets in the building have 242volts but obviously cannot test anything once load has been removed like I can on the three phase circuits.Have you verified the neutral St the distribution board.
Is anything else in the building suffering from a potentially floating neutral.
He is worried about this voltage.So what does the customer make of this
2 days in, a call out from the DNO and still no solution.
You say that the neutral is only at the contactor for a pilot light.
What goes to A2?
Is your plant a 3 phase ungrounded delta or is it a 4 wire y connection and is the line voltage 600 or 480Hi
I have been called out to a fault on a grain dryer where the motor interlocks are not disconnecting. Previous conveyors. Upon investigation I have found one starter that does not disconnect the preceding motor but when tripped I am getting 550v to earth from a1 and wait for it 760volts to phase from a1! This has baffled me as there's only 410v incoming.
Thoughts?
I don’t think it’s in the control aspect of it. You have a power problem not controlsIs your plant a 3 phase ungrounded delta or is it a 4 wire y connection and is the line voltage 600 or 480
Is your plant a 3 phase ungrounded delta or is it a 4 wire y connection and is the line voltage 600 or 480
the voltage in the states for a house is normally 120/240. When you lose your neutral the 120 will go up to 190 which will fry clocks, TVs or anything plugged into to the sockets which we call receDo y’all use ground rods to bond your service.We're in the UK, our voltages are different, and we don't use delta supplies. Our normal service except for new, very large installations is 230/400V 4-wire Y. So anything over about 430V is abnormal.
Let's look at the possibilities.
1) The high voltage does not exist. The voltages being shown are not the actual voltage present, due to interference from a VFD or similar, causing the instruments to malfunction.
2) The voltage actually exists, and is coming from the supply. This doesn't make sense. If you lose the neutral on a 230/400V supply, 230V single-phase circuits can receive anywhere between 0 and 400V. 3-phase circuits will still have 400V between each phase and another, but the neutral could be anywhere from 0 to 400V from each of them. Nowhere does the voltage rise above 400V.
3) The voltage is being produced within the panel / system. I don't think it's been explicitly stated what the control voltage of these contactors is. Do some / all of the coils operate at 230 or 400V? If there is a control transformer in the panel, a fault on the secondary that puts it in contact with a line of the primary, could add their voltages. It would be possible to have say 510V from one 110V control wire to one line wire, if the other side of the control supply is in contact with another line. There are some very unlikely scenarios that we could think up, where isolated devices that can behave like transformers could add to make higher voltages still.
But all of this is just conjecture if we can't see the circuit!
Bonding the neutral is the most important thing you can do and we call sockets receptacles in the statesThe
the voltage in the states for a house is normally 120/240. When you lose your neutral the 120 will go up to 190 which will fry clocks, TVs or anything plugged into to the sockets which we call receDo y’all use ground rods to bond your service.
Bond
Bonding the neutral is the most important thing you can do and we call sockets receptacles in the states
No we don't install earth rods to connect to neutral here, our distribution systems are reliably connected to earth at the substation.
Well, we do. Just not in public houses.
learning something new on how you do things in the UK. It’s like a different world with all the different voltages and standards.Well, we do. Just not in public houses.
Don't do much in the way of Safe isolation then in your place of work?So when the contactor is off and the machine is isolated.
What is the continuity between
L1 Common and L1 Load.
L2 Common and L2 Load.
L3 Common and L3 Load.
Also when the coil is de-energising does it completely release, or is it mechanically stuck half way. Does a crack with a screwdriver properly release it?
The 110v is a waste of time. It sounds like you are testing at 2 points on the same phase. Unless the control circuit to pull in the contactor is 110v. I just can't tell from here.
You need to always test the lives with one prong on phase and the other on the earth bar.
Don't do much in the way of Safe isolation then in your place of work?
Reply to Volt meter reading 760volts in 3phase dol starter overloads in the Industrial Electricians' Talk area at ElectriciansForums.net
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