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Are the Electrics Right in ME4575?

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Brian Sweeting05/12/2017 13:55:09
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Posted by Brian G on 05/12/2017 08:45:28:
Posted by Brian Sweeting on 04/12/2017 22:21:22:

Looking at Fig 2 in the original post I would consider it dangerous because even in the 'off' position there is still the potential for a voltage to reach the motor.

Although the neutral should be at 0 volts a fault upstream would feed through the relay coil to the live feed to the motor or your fingers if you are during some wiring mods at the time.

Isn't that what the isolator is for? I wouldn't like to work on anything only separated from the mains by a contactor - if the neutral breaks correctly but the live contacts have welded, the motor would be live even though it had stopped. (Although this wouldn't happen in Fig.2 as the contactor is fed from the live contacts, so if the live contacts had welded the motor would re-start immediately the N/C button was released.)

Brian

Agreed that the isolator should be used, perhaps my wording was unclear. In fig 2 the machine is not separated from the incoming neutral in the off state. 

Any neutral fault upstream could be fed to the machine, unlikely, sure.

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