What will happen if L-L 440 Volt passed through 230V MOV-2798844 (Phoneix Contact)

[Shivam Maury]

Hi All,

I have a question regarding my control panel, As camera and framegrabber is failing frequently.

1. Can we connect 230V phoniex contact MOV-2798844 between L-N if yes how it'll clip off the voltage? (There is no earthing point going how it'll pass out extra voltages)
2. Can we connect 230V phoniex contact MOV-2798844 between L-L if yes how it'll clip off the voltage? (Will is burn if continous voltage is going)
3. Can we connect 230V phoniex contact MOV-2798844 between L-N+PE if yes how it'll clip off the voltage?

 

[3DDave]

An MOV works on voltage differential and can do two things -

1) clip very short high voltage pulses
2) provide a sufficient short circuit to cause slower devices to interrupt the current.

See

https://www.mouser.com/pdfDocs/ApplicationsofMetalOxideVaristorsMOVinPowerSupply_en.pdf

for more application information.

MOVs typically fail by becoming a short circuit. If there aren't devices that can trip on that current they can start fires or burn out to become open circuit. Adding an MOV by itself without consideration of fuses or other over-current protection is a waste of time.

See also:

https://m.littelfuse.com/~/media/el...elfuse_varistor_mov_products_training.pdf.pdf

 

[waross]

Voltage above the cutoff of the MOV is dissipated as heat in the supply conductors.
Example. 120 Volt cutoff. 150 Volts applied. The MOV will draw sufficient current to cause a 30 Volt voltage drop in the supply conductors.
The actual current will depend on the resistance of the supply conductors and on the %regulation of the supply transformer.
Example 2: Compare; 300 feet from the transformer to the MOV.
Case #1, There is a 200 Amp panel adjacent to the transformer and 300 feet of #14 AWG conductor to the MOV.
Case #2, There is 300 feet of #0000 AWG conductors from the transformer to the 200 Amp panel and 12 feet of #14 AWG conductor from the panel to the MOV.
You can see intuitively that it will take a much greater current to drop 30 Volts across 600 feet of #0000 AWG than the current required to drop 30 Volts across 600 feet of #14 AWG conductor.
(About 64 times as much current.)
Transformer regulation will reduce this a slight amount.
It depends.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[che12345]

Mr. Shivam Maury (Electrical)(OP)18 Jul 23 04:39
"....I have a question regarding my control panel, As camera and framegrabber is failing frequently.
1. Can we connect 230V phoniex contact MOV-2798844 between L-N if yes how it'll clip off the voltage? (There is no earthing point going how it'll pass out extra voltages)...."
2. Can we connect 230V phoniex contact MOV-2798844 between L-L if yes how it'll clip off the voltage? (Will is burn if continous voltage is going)
3. Can we connect 230V phoniex contact MOV-2798844 between L-N+PE if yes how it'll clip off the voltage?"
I assumed that your 3-phase with solid earthed neutral is L-N=230V, L-L=230V x 1.732 = 400V.
1. Yes, you can connect the [230V MOV] across L-N. When voltage L>N , discharge current flow from L to N. When voltage N>L, the discharge current is reverse. No earthing point is required.
2. When L-L =400V, you MUST connect two 230V MOV in Series as a 460V unit. That is, Six pieces of 230V MOV, two in series as a unit connect across L1-L2, L2-L3, L3-L1.
3. Suggest following for a complete protection:
a) one 230V MOV each connect across [L1-PE], [L2-PE], [L3-PE] and [N-PE]; and [L1-N], [L2-N] and [L3-N], and add,
b) two pieces of 230V MOV connected in series as a single 460V MOV unit connect across [L1-L2], [L2-L3] and [L3-L1].
What a BOMP!
Che Kuan Yau (Singapore)