does missing neutral line from a 3 phase source lead to problem in the device connected to it?

Thread Starter

layana

Joined Oct 16, 2020
1
hi,

A 3-phase AC(Air Conditioner) inverter training model connected to a 3-phase plug (plug 1) was working without any problem, but when the 3-phase plug changed to another one(plug 2) the model didn't work and the circuit breaker of the model went off and each time trying to run the model the same problem exist. then the model connected to plug 3 for one time and the same problem exist.

when the company from which the model was purchased came to check the problem , Electrician tell that the plug 2 L1,L2,L3 and E connected but N missing and source 3 L1,L2,L3 connected and N missing but E line connected to N of the 3-phase plug.


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when the control board of the module checked by the company they tell that the following component need to replace diode (rectifier) , capacitor and ipm module in inverter board.

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does missing the neutral or use E instead of N make this problem ?

which mainly damage the components connecting it to plug 2 or plug 3 ?

L
 

andrewmm

Joined Feb 25, 2011
671
Two wasy to look at this,

a) The evidence is that wiring it up different to that defined as right, causes a problem.

b) Going back to my old theory, neutral, in theory in a balanced 3 phase is not needed. BUT , you don't know if the company have a mixture of three phase and single phase stuff in the box. QED, point (a)
 

Ramussons

Joined May 3, 2013
890
Two wasy to look at this,

a) The evidence is that wiring it up different to that defined as right, causes a problem.

b) Going back to my old theory, neutral, in theory in a balanced 3 phase is not needed. BUT , you don't know if the company have a mixture of three phase and single phase stuff in the box. QED, point (a)
Exactly. That may be some control unit.
Or, when replacing the plug , there has been a Phase Interchange in wiring Plug 2 that has been carried on to the plug 3 change too.
 
Chances are if you didn't need a neutral connection there wouldn't be one in the first place. They wouldn't spend the money to include it or waste miles of wire just for kicks. On the incoming service end 'E' and 'N' usually end up at the point somewhere, but on the device end 'E' and 'N' are different connections and can't be interchanged, left out, or otherwise not done correctly.
 

crutschow

Joined Mar 14, 2008
25,680
Yes, the phase sequence is also critical, as a three-phase motor will run in the opposite direction if the phase is reversed.

I worked on an Army system that used a small three-phase motor as part of a cryogenic cooler for an IR sensor array.
It got plugged into a socket with a phase reversal which caused the motor to heat instead of cool the sensors, which damaged the sensors to the tune of many thousands of dollars.
 
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