Best Relay for a Motor

[Neil Scrivener]

Hi Guys,

I have a 'garage' style electronic hoist.

An example of the type is: Hilka Pro-Craft 500kg Electric Hoist | Workshop Equipment | Screwfix.com

As you can see there is a two position switch, and inside there are some capacitors for starting voltage. The Switch on one 'side' is Live, and the other 'side' Neutral.

What I'm looking for is to replace this switch with a Relay, so that I can control this from a distance over Low Voltage (ie 12-24V).

I'm happy with all the principles of the wiring, but wondered what anyone can recommend in terms of a Relay that would be be a suitable replacement for a switch?

Cheers
Neil

 

[Darkwood]

Are you sure that a 2 position switch and not a 3position center off switch?

 

[Neil Scrivener]

Sorry, you are completely correct!

Yes, I meant 2 position 'on switch'. But yes, 3 position, centre is off.

 

[telectrix]

i'd be wary of modifying it for safety reasons. also, if anything untoward happened, the manufacturers would disclaim any liability.

 

[Darkwood]

To really give an answer we need a bit of info -

-What voltage is the motor and how many phase (I assume 230v single phase here as you mention starting cap's)?
-Is the switch motor load bearing or just a low load control circuit?
-You say your OK with the wiring side so are we to assume you are knowledged in the BS60204 which will cover how you go about doing what you wish, as you will have to consider some form of electrical and mechanical interlock to ensure you cannot by operational error or electrical/machanical failure have the motor been told to go in both directions. (this can be achieved with a mechanically interlocked F/R contactor set up).
-Your safety system will also need extending if the pendant isn't been used, if you are adding additional actuation points to the existing this may mean you change the requirements of the control voltage and the protective measures like an isolating transformer may need to be incorperated.

What at first seem a simple adaption becomes a little more costly, these existing controls are often designed to fall below certain requirements and are made very simple but the act of adding or extending these systems can often change the requirements of the original controls thus make them non-compliant.

 

[Darkwood]

Your safest bet here is to just extend the existing pendant to the required length, you will still invalidate the warranty and put all responsibility on your shoulders as the designer of the control circuit even if its just to extend it...(if someone is injured or worse by this equipment, you will need to show that any alteration you did did not compromise the safety of the equipment and more so, complies to the current regulations) also to add just for your own clarity here is Low Voltage is what I assume the controls are already (230v), 12-24v is classed as Safety Extra Low Voltage, these minor descriptive errors are why I ask if your knowledged with the EU Low Voltage Directive namely the BS60402 as their is a section of this that covers the requirements of lifting equipment and cranes etc as well as the general requirements for the control side.. together they have a bearing on what you are and are not allowed to do here, like has been said, its not just as simple as making a functioning control circuit and incorporating it to the existing.

 

[SheffSimon]

Your safest bet here is to just extend the existing pendant to the required length, you will still invalidate the warranty and put all responsibility on your shoulders as the designer of the control circuit even if its just to extend it...(if someone is injured or worse by this equipment, you will need to show that any alteration you did did not compromise the safety of the equipment and more so, complies to the current regulations) also to add just for your own clarity here is Low Voltage is what I assume the controls are already (230v), 12-24v is classed as Safety Extra Low Voltage, these minor descriptive errors are why I ask if your knowledged with the EU Low Voltage Directive namely the BS60402 as their is a section of this that covers the requirements of lifting equipment and cranes etc as well as the general requirements for the control side.. together they have a bearing on what you are and are not allowed to do here, like has been said, its not just as simple as making a functioning control circuit and incorporating it to the existing.

For clarity, darkwood meant to type 60204, rather than 60402. Everything else is spot on, it might look simple, and no doubt you can get something working, but one day your circuit might not work as you expect. Then somebody might get injured.

 

[Darkwood]

Cheers Sheffsimon... Tiredness and speed typing is my excuse :yawn:

 

[Marvo]

I would also just replace the cable with a longer one rather than alter the fundamental design.

 

[Neil Scrivener]

Hi Guys,


Sorry I should explain who I am, and what I do better.



I work usually in music touring - I set up very large stage lighting rigs in Arenas all over the world for bands/artists, probably well known to you - and spend most of my time dealing with multiple 400A Three Phase supplies, and distributing them over hundreds of lights. So I'd like to think I am more than competent in the re-wiring of a small project as simple as this



Part of my job is using CM Lodestars (check them out) which use a 24V Control Voltage, so I know pretty well what the end result I'm looking to achieve is. In this regard, I am fully familiar with the Health & Safety regs that need to make this compliant - perhaps more so, because in my industry motors sit above an audience of several thousand, or a band worth several million!



The Motors are single phase, have 13A Plugs, so that's really easy, I can do that bit with ease!



The reason why we want to put this relay system in is because 4 motors will be mounted on a test truss, and for safety I need to be able to control them all at once, as obviously if you don't run them simultaniously, the weights change per point, and so forth.



Basically I want to use relays; somehow, replace them with the switch - and then there will be a low voltage hand controller with 4 switches and a 'go button' which will control each motor depending how (or not) the switch is selected.



The concept, I do every day quite simply, we have off the shelf products that do this (google Outboard Electronics) - I just need to convert these particular motors for this purpose - and the off the shelf products in our industry are not compliant with how the motor appears to be wired, or within budget.



Cheers

Neil

 

[Darkwood]

Thanks for the update, the area of work you are in explains your mix-ups with the terminology we use everyday and you probably don't.

If your happy and well versed in the relevent regulations and H&S requirements then I'll not preach the mountains of regulations to you anymore...

I would require a wiring diagram of the motor/control to advise correctly, but basically you have a raise and lower option you need to extend and mimic with a contactor arrangement, also because the existing switch operations prevent mechanically the chance of the motors raise and lower option been chosen together you will need to do this with contactors - you can get a Forward/Reverse pre-arranged contactor with mechanical interlock to prevent the motor been called to go both ways be it through error or failure of parts, also using auxillary contacts to give electrical command isolation too.(Fail safe)

 

[davesparks]

I also work as a production electrician/lx tech/rigger/fly man but that doesn't qualify me for jack-sh*t in terms of motor control wiring.
You're now in the territory of the low voltage directive and the machinery directive whereas rigging is normally more in the realms of loler and puwer

 

[Neil Scrivener]

Darkwood, I'll have a dig around next week and send some pictures probably won't be until next week.

With respect, Davesparks, I think you've missed the point - with respect, our outlook in the side of the industry we work in may be a little different from a theatrical one

 

[davesparks]

With respect, Davesparks, I think you've missed the point - with respect, our outlook in the side of the industry we work in may be a little different from a theatrical one

What is the point then?

The chain hoists used in all parts of the entertainment industry are the same, just industrial units painted a different colour. They all turn up as plug and play units with the control systems pre-built with all the electrical safety considerations taken care of.
The closest you get to any controls wiring is if you are installing the hoists permanently when you get a wall mounted control panel rather than a rack mount one.

 

[Neil Scrivener]

The point is, this item is purely for a testing area; not to be used in a 'live' environment on site.

The users of this machinery are fully competent to use it. Likewise, we as a company (who own 40+ motors in production/rental stock) have fully competent personnel who are capable of the wiring - we build our own mains distribution up to 400A, as well as manufacture various cables for clients. We have personnel that can sign of to BS7909, BS2395 etc - this specific area is simply out of our typical scope of work, but it doesn't make us stupid. I presume as a ''rigger'' you hold an NRC ?

What you say about installed Hoists is, with respect, irrelevant. Installed motors, as perhaps you know will tend to be 3 phase Direct Control (ie switching the phasing) - or in some occasional cases LV control. This is some lightyears away from what the hoist in question is, and in any event DC or LV 'bog standard' controllers would not work for this application.

We are simply looking for some advice on an alien (to us) area of electrical world, hence I joined up to see if we could find some sensible assistance. With respect, I feel the need to plead the case of competency more than actually get to grips with the nitty gritty of the original question.

For the sake of sensibility, could we kind of move on from the concept that there is an element of 'danger' involved? I assure you we have fully scoped this area....