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Max Ngwira
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Join Date: Nov 2011
Posts: 13

Cooling Fan Earth Connection

03/29/2012 12:20 PM

I want to install a 220V cooling fan in a 380V welding machine. The supply to the machine has no neutral provision. Is it okay to connect one phase and earth to supply the fan? The main power supply transformer's neutral is also earthed.
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PWSlack
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#1

Re: Earth connection

03/29/2012 12:24 PM

Nope. That connection would fail a periodic workplace portable appliance test under British Standard 7671. The reason? One loose earth wire connection where the machine plugs in, and someone using the equipment is going to get electrocuted.

Either change the cooling fan for a 380V one, or add a 380V-220V transformer - suitably rated and protected, of course. If in doubt, consult a competent electrician.

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mike k
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#2

Re: Earth connection

03/29/2012 12:36 PM

Max, let us know what the voltage is on the individual wires to the welding machine. In the US, it takes two wires to get 220 volts, single phase. A 380 volt machine would have three wires if it was three phase, two of those wires could be used to make 220 volt single phase.

Please list where you are, and the type of electrical service you are using, it varies around the world. We can't make decisions not knowing all the facts.

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Max Ngwira
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#4
In reply to #2

Re: Earth connection

03/30/2012 11:19 AM

Mike, two wires feeding the welding transformer. Measuring the voltage between them=380v, between one wire to neutral= 220V, between one wire to earth=230v. 380v is the standard 3 phase industrial voltage here.
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mike k
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#6
In reply to #4

Re: Earth connection

03/30/2012 4:50 PM

It looks like your machine is single phase. Anyway, you will need a 380/220 transformer to drive your fans safely.

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SolarEagle
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#3

Re: Earth Connection

03/29/2012 1:12 PM

A detailed schematic diagram would help....

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mike k
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#5
In reply to #3

Re: Earth Connection

03/30/2012 4:47 PM

Wouldn't it be safer if the main power switch broke both feeds?

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