Motor starter

Hello all

I may have been in a dim moment today but here goes. I have someone with a 4 post car lift, that's the easy bit. The motor has gone which is no surprise as someone has made there own 3 phase to 240 convertor box. So I have a new single phase 3hp 240 volt motor, but my problem starts with what contact and overload do I fit. The motor is actioned by the up/down lever (micro switch) but if I get a standard DOL it won't stop the motor because it does not cut the power on release of the lever. So not having too much to do with Motors over the years I having a bit of trouble with which one to fit, I don't need a start button because of the micro switch an E stop would be nice, but can fit a separate one.

Any help would be greatly received or if I am been a muppet 

Mark

is this a lift in someone's house (probably not) or a commercial garage, in which case various other legal requirements will apply?

Presumably has to reverse too ?

Geoff1946 said:

Presumably has to reverse too ?

Click to expand...

he mentions levers, sound more like hydraulic powered up gravity down so no direction or motor control needed, unlike if it was mechanical screw type

Have a look in Knowledgebase, I've covered it in there.

Just remember that in a workplace, this comes under EAWR, PUWER, LOLER, & SMSR!

As Sidewinder says, just remember the regulations because if anything were to go wrong you could be classed as having made untested or unapproved modifications, this could result in you having an unpleasant meeting with a guy in a funny wig to explain why you did what you did.

Long in the tooth said:

The motor has gone which is no surprise as someone has made there own 3 phase to 240 convertor box

Click to expand...

What do you mean by that?? Are you sure...

john...

Hi guys 

It is a hydraulic four post ramp and it's in a private home. And I am putting it back to what it should be and not the mess it is now. But please don't worry if it's a problem I'll pass it off to some other muppet

If it is anything like the 4 posters I have worked on, the motor powers a hydraulic pump and only runs when the "up" pushbutton is pressed, and down motion is achieved by pressing a button (to release a clamp) and pushing a lever that slowly releases the hydraulics.

No need to pass it on, it’s easier than wiring a house, just a lot more rules to follow!

Please remember that all we know about it is what you post! 

I would think just buy a suitable contactor rated for the full load current of the motor, an overload relay to go with it, and the micro switch powers the coil.. Photos of what you have there now would be good.. Why do you think the original motor failed?? What motor is/was it..

john..

It was a 3 phase Brook Crompton. Many years ago someone did the work on it and fitted a box of contactors, 3 coils and timers to make it run on 240 volt. Sent it off to motor tester who said it was toasted and would be to much to repair. When there isn't any 3 phase in the property so he can't tell me what went on in the past  I wish I could workout how to put photo's on ? All the original equipment had been changed apart from the micro switches. So just want to fit back as was with a 240 motor because they do make the ramp with 3 phase and 240. But can't get any equipment from them any more. All I now is I need a contactor with overload to work off the micro switch to take it one way no reverse needed. 

So your overload needs to be set to motor FLC, so that gives you the range for that.

The contactor needs to have a coil at control voltage, with adequate main and auxilliary contacts to switch what you need to, and the main contacts need to be rated at, preferably, above motor FLC, the contactor OEM will give you data on the motor size that it will swith.

So, sorted! 

Sidewinder said:

So your overload needs to be set to motor FLC, so that gives you the range for that.

The contactor needs to have a coil at control voltage, with adequate main and auxilliary contacts to switch what you need to, and the main contacts need to be rated at, preferably, above motor FLC, the contactor OEM will give you data on the motor size that it will swith.

So, sorted! 

Click to expand...

That's great Sidewinder you wouldn't have a drawing for the layout please. I'm working away until 23rd but will let you know the motor details.  

What layout?

Microswitch is control for coil, motor is the load, no sure what else a spark needs to know.

I don’t know the detail of the machine to say what wire is what!

As @Sidewinder said...it's standard motor control theory 101.

like almost 99% of our trade skills it is probably not taught anymore 

Well, you need a contactor that is rated not only for the FLC of the motor, but ALSO for "AC-3" duty..

I would suggest one of these...

https://uk.rs-online.com/web/p/products/3949699/

Then you need an overload relay to go with it..

I would suggest one of these..

https://uk.rs-online.com/web/p/products/3949324/

Yes i know they are three pole ones, and you have a single phase motor, but when i looked up the price of single pole ones, they were much more, and i could not find overload relays either..

What voltage are you using for a control voltage?? The contactor above is a 24v one..

Do you know how to wire the thing up??

john..

Thank you all, now done with no loud bangs so that's a plus. And it run's the pump too. Thanks again guys have a good one