Mains Contactor Box

[rtbcomp]

Having a few bits & pieces kicking around doing nothing, I made this:



It allows me to test motors &c, it's fitted with an RCD and no-volt release. There is a pedal which can be used to turn the power on and off or work as a dead man's pedal:



And just for good measure there's an LCD panel which shows voltage, current, power and energy consumed:



The red neon on the 13 Amp socket shows it's live and the green neon next to the start button lights when the unit is ready.

 

[Kayos]

What does no-volt release mean?

 

[hotponyshoes]

No volt release means:
Once it is switched on it requires the power supply voltage to remain on.
If you get a power cut or the trip cuts out then the switch will automatically turn off.

So the machine/motor etc won't turn back on when the power comes back on.
Safety feature. Most drills, grinders, machinery with moving parts come with them fitted.

I have them fitted to all the extractor fans in the workshop so I can start them up as I need them can just flick one switch at the end of the day and they all turn off.
When I turn the power back on they don't all start up again at once!

 

[slim_boy_fat]

What does no-volt release mean?

I just bought one of these for the mill - will have to wait until the matching enclosure box is in stock as I want to surface mount it.

 

[rtbcomp]

This is the circuit which controls the contactor:



With the relay de-energised (ie footswitch unplugged) the contactor coil circuit goes

Live > Coil > RLA/1 NC > Start Button & Contactor contacts

There is a current through the neon sufficient to illuminate it but not enough to call the contactor.

Pressing the start button the circuit continues

Start button > Mode Switch* > Stop Button > Neutral

The contactor calls, maintaining the current through the coil thus:

Live > Coil > RLA/1 NC > Contactor contacts > Stop Button > Neutral

This provides the no volt release function in that if the power fails the contactor drops out and will not re-energise unless the start button is pressed.

*Note - with the footswitch unplugged the mode switch is ineffective, as RLA/3 NC connects both ways of the switch together.

 

[rtbcomp]

Added a dimmer/speed controller. This is a generic Chinese triac unit which controls resistive loads or universal motors such as found in washing machines and power tools.