using an inverter to power a 3ph hoist

Gentlemen,

I have a friend who in the last year has lost both his legs below the knee's and to keep his interests going I and others have been modifying his sheds to allow him to carry on with his hobbies, lowering benches etc so he can work from his mobility scooter etc.

He recently bought a second hand 250kg electric hoist and carriage which is 3ph, he has two sheds, a small one of 40' x 20' where the hoist has been fitted and a bigger shed 40' x 40' which is where the 3ph supply is which means we have to run 50 metres of cable to get the power to the little shed.

My question is is there any reason why we couldn't run the hoist off of a correctly rated inverter from the existing 240 ac supply which we have recently installed.

Martin P

I cannot answer your question, but if you contact REMAP ( http://www.remap.org.uk/ ) they have regional panels. These are mainly manned by retired engineers and our remit it is to make specialised aids for disabled people. We don't charge, we just work on donations.

They should be able to help with your friends modifications.

Thank you for you response, I'm a recently retired Engineer and am aware of REMAP and another friend of mine is a retired Electrical Engineer, we are both confident on what we do for him and we don't see an issue ourselves we are just looking for other views on the subject to make sure we dont miss anything.

Martin P

Martin, as long as the motor can be delta connected I see no reason why you can't run from single phase supply, indeed the inverter method will provide adjustable ramp up and down speed control which may be an advantage for the user.

Emgee

The area I would look at is the brake. If it is entirely mechanical no problem. If it is spring apply electric release it should be ok but probably wouldn't allow for variable speed/ramping.

Many inverters will have a built in relay which can be used for things like operating the brake (check supply voltage for the brake). I know that some have built in functions specifically for use with braked motors - I've used them in a different application. When used in this way, a separate cable (or extra cores) is required for the supply to the brake unit.

Hi it is important with inverters that the connections between the inverter and the motor are direct, so you would have to use the low level controls on the inverter for up and down control.

HTH

Chris

Hoists sometimes have an ultimate limit that breaks the phases to the motor, some inverters object to having the load disconnected while driving, if your hoist is like this then check the inverter can tolerate load disconnection.

Mike

Thank you gentlemen,

Some points for me to check, I doubt the user will want variable speed so that will be fixed, he cant wire a plug without instructions so no problem of fiddling