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

 

[davesparks]

I'm not familiar with BS2395, what does that cover?
Being a testing area is irrelevant, the exact same legislation covers the machinery controls, emergency stopping etc.
Actually I think all of the installed systems that I've fitted have been elv controlled as it allows limit switches to be used.
I would have thought a setup similar to the bog-standard controls would be best for your application as you will presumably still want the individual control for levelling? You could imitate the standard setup completely with an elv transformer and relays at each motor connected back to some yellow commando sockets, then you'd be able to use your existing elv controllers or build a little panel for it.
Or else you'd need the same relays at the motor but with the elv source in the panel.
But either way the e-stops are presumably going to be cutting the supply to the motor?
I think your original question was about relays, any standard industrial relay with the right coil voltage and a contact rating at least equal to that of the switch currently used should do the trick.

 

[Simonslimline]

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

Sorry to be a sad nitpick, but this is Extra low voltage.

:rolleyes2:

 

[Englishman]

Sorry to be a sad nitpick, but this is Extra low voltage.

:rolleyes2:

It consistently winds me up as well mate, everyone calls 12v LV and not ELV.

 

[Darkwood]

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....

We are not questioning your competence in your own area of work but by your own self admittance you are trying to do work that takes you into a totally different area of legislation and regulation, we are trying to point this out to you, regardless of motors been 1ph, 3ph AC,DC etc the very act of trying to alter or combine control for multiple motors will mean you have to comply to other regulation you're probably unaware of, of which we are trying to advice you, I have already hi-lighted certain criteria you may need to meet but from your explanation I believe you would be required to intergrate a critical safety circuit common to all motors, electro/mechanical interlocked directional controls, possibly a global monitoring system to ensure like you say that load is kept balanced.
We lack so much info here to give tailored advice tbh but from what you have given it does strongly lean towards the need to meet the EU Low Voltage Directive and as already mentioned you will be falling under the 'Safety of Machinery - Electrical Equipment of Machinery'.

We are not trying to trip you up here, the manner of you question and what you want to achieve all point to a need for you to comply to the suggested regulations, the area you work in, be it stage lighting for a concert to production line machinery is irrelevant here, they all have to comply to the same regulations when designing the control systems.

When we bring up this subject you repeatedly reply you are competent and fully aware of the regulations you have to comply to yet this does not show in your replies and the actual questions you are trying to ask... if you are linking these motors together to a common control system you effectively alter the requirements the original motor controls were built to and makes them non compliant - you cannot simply extend the control of 4 seperate motors hoists to a common control system (yes that is simple in theory and practice and probably would work, but falls far short of requirements.)

All we are doing by dragging this out is to ensure you are aware of the correct regulations you have to adhere to, so far you have not shown this in your replies. We want to avoid giving misleading advice here so with all respect to the knowledge you have in your own field, we are asking you to realise you maybe entering a whole different level of your work to that which you are used to.

 

[UNG]

Isn't it strange that similar threads appear on other sites and once rebuked the OP moves on until someone gives them what they want to hear

 

[Darkwood]

Isn't it strange that similar threads appear on other sites and once rebuked the OP moves on until someone gives them what they want to hear

I take it he's been doing the rounds then, I just think on this occasion the OP is ignorant of the regulations that cover what he wants to acheive and believes the regulations he works to are enough, I haven't suggested at any point the OP isn't competent in his own field.
From the info gathered I personally wouldn't have bought off the shelf units complete with control pendants to convert but instead bought the motor rigs without controls and designed from their - running them either of a single VSD or 4 separate with coupled speed ref' to ensure all motors behave the same.

Its not cheap but he says their is a budget... Sorry but H&S don't allow corners to be cut because of funding, million pound bands, millions taken on the tickets yet skimping on a few grand to have a safe control system to meet regulations, :nonod: I have personally never known a budget not be revised for safety if your case is presented correctly - it could be argued the insurance could be invalid if found to not meet regulations thus no concert/gig!.. bet the limiting budget would suddenly be relaxed.

 

[Lucien Nunes]

As I understand it, you want to substitute single-phase utility hoists with integral pendants, in place of conventional rigging hoists designed for external control, for what would otherwise be a standard multi-motor truss controlled from a normal riggers' handset. I presume the reason is one of economy or lack of available 3-phase supply? You recognise the interfacing your handset with the original wiring of the alternative hoists involves relays of a certain minimum specification, hence your question, although that was worded to suggest a single hoist.

If you know the spec of the original control circuit, then it is a simple matter to spec a relay that will function electrically. I don't think you've stated this yet? The problem arises, as others keep suggesting, that the choice of relay is dependent not only on the electrical requirements of the hoist but also the degree of safety it needs to provide to ensure that the complete multi-hoist system functions as intended. What would be the risk involved if one relay welded shut and caused one hoist to run while the others were stopped? What if one motor started up in the opposite direction, stalled, or reversed while in motion (a single-phase motor may be more prone to this than conventional 3-phase rigging hoist motors)? These are factors concerning the integration of the hoists into a system that demand an overall risk assessment outside of the scope of what we can advise on a forum. You state that you are competent to do this, and I am not personally doubting you, I just don't think we can make any useful recommendation about the choice of components from a distance, for such a critical application.

 

[Darkwood]

On that last note, I think the OP is now well informed that he shouldn't be trying to mess with such systems as he has failed to convince me he has any knowledge of the requirements and regulations surrounding what he wants to do.

In the interests of the safety of the OP and unfortunately the safety of Justin Beiber as well, I'm closing the thread.