Star-Delta motors on plugs and sockets

It's not something I've had to do before and Google hasn't come up with any suggestions for me either. I can only suggest getting your hands on 6P+E plug or socket and see if the terminals are labelled usefully.


Even if there no standard pin-out, and you had to impose a site-specific standard, I would have thought it would still have been useful (e.g. allowing quicker swap outs, obvious isolation etc) - it's not as if motors come manufactured with moulded on plugs, like domestic appliances.


  - Andy.

Correct me I am wrong, but I seem to recall from my days working in heavy industry that motors rated at more then 1/2 HP were not permitted to be on a plug and socket arrangement.

Have things changed in that regard? It was something which the Factory Inspector raised at one of our monthly meetings, and as a consequence, we had to down-rate our conveyor motors to 1/2HP or under to comply.

It may be more of a H&S thing in mines/quarries/factories etc, rather than a BS7671 thing.

Also, they didn't like 3 ph stuff on 440V trailing leads either.

I think the replies are accurate here, I don't think there's a standard, but a written risk assessment (are there any other industrial sites nearby using similar connectors for example) would show 'due diligence' If you're going to take the plunge, make it site-wide, provide documentation as to the 'standard' connections.  That's the kind of thing the H&S bods are looking for.

You may also need a method statement & risk assessment for swapping the motor, to cover off someone trying to plug in a mechanically loaded motor with the starter on and already in”delta” mode. Depending on how well rated the connectors you use are, the result could be exciting. 


Regards,


Alan.

thanks for the replies. 


the motors are 22kW and in a hard to access mechanical cellar, 6m deep.


since the plant has to be isolated to go into the cellar, that procedure is already in place to prevent it being plugged in in delta 


The reason I want to do this is that when one fails, the mechanical fitters go down, uncouple the pipes, unbolt it and crane it out, and they usually disconnect the armoured cable from it (with the usual bits of tape labelling the cores) 


I think that alone is enough of a reason to improve the setup.


a site standard (assuming the plug isn't labelled usefully has to be the way forward. Could even label the socket accordingly



we have reduced our 400v extension cables now and those that remain have RCDs on them, except welders, which are still 3ph 32a but only used for maintenance. We did have 300hz 200v 3ph supplies a while back, they were always exciting.

Get an 11+ pin plug something like a Harting (other makes are available) and run the e-stop system through the plug too, that way it has to be plugged in to allow the system to start, unless you have a dummy plug, plus you can get the right pins so they break correctly to e-stop before they break the power connections.

Oh and you can also get coding pins so that they can only be fitted in the right way and the right place, unless you re-configure the plug, but then that can be said of any plug which can be opened up.

Interesting thought, but it would mean quite extensive rewiring. There isnt much of a consequence if the system were to start with the pump disconnected anyway. 


in fact, im thinking now, someone did a plug with a pilot contact in the socket end for a stop circuit

Te be honest it's not the starting without a motor connected, it was the disconnecting on load I was more concerned with.

Be careful about a single contact for e stops because they should be PLc, which may mean dual channel.

This is why I suggested a configurable Harting (Other makes are available) type as they can be metal hoods, IP 65 (if needed), configurable pins, and coded to the base so they can't be plugged in the wrong way/in the wrong place.

All of those things go to ensuring that you may still comply with the safety standards for e-stops.