Created Date: July 01,2016

Created by: Randy Simpson

Hello, I am not a VFD expert, and if someone can answer this question I would greatly appreciate it.

I recently purchased a cable hoist with a 15hp three phase motor "cheap " 400 bucks considering a new one is 4 grand, it has 10 times the hoist capacity that I actually need. My question is the capacity at full load is 3500 lbs., I will only need 350 lbs., I only have single phase 230v power, can I use a 10hp VFD to run a 15hp since the motor will only be fractionally loaded. Any drive over 10hp that I have researched needs a 3 phase input. My guess is at 350 lb load the motor amps will be around 1/3 of full load which is (38amps). My guess is at 350lbs. the load will be around 12 amps.

Created Date: July 01,2016

Created by: Cap

I do not fit the Expert category Either.. But I 've help burn up a lot of stuff..

The Problem is the 15 Hp Motor is a BIG Coil.. the 10 Hp Drive SHOULD not have any real issues powering it through single phase as long as the Amp Load is low.. I 've done stiff like this before.. but not at the extremes you are doing it..

You will have to drive the For/Rev Switch on the Freq Drive from the For Rev Contactor in the Lift.. use the Contactor Contacts to actually sig the Freq Drive to For/Rev.. You do not want to disconnect the Motor leads from the VS Drive so NO Contactor between the VS and the Motor.. Have the Brake be your 'Ultimate Safety ', as you will now not have any 'Positive Disconnect means ' to power off ( Safe ) the Lift Motor.. as it will always be connected to a Live Drive..

Carefull about the Brake Coil.. you will need to power that separately.. You will have issues getting the Acceleration Rate set proper to reduce the Inrush Amps, but not let the Lift Coast backwards before the Freq Drive Gets the Motor Powered Up..

ANOTHER odd ball way is to use a Capacitor Bank to drive the 'third Leg ' on the Motor.. It's 25MF per HP for the Run Cap, and Ten Times that for the Start Cap.. if you are in the 15 HP range things get big.. but it depends on what you have available..

I'd try the freq drive ..

Cap

Created Date: July 05,2016

Created by: deep6ixed

I'm not an expert by any means, but I do work with both drives and hoists. This is a real big area of liability. Our main lifting hoist for our welder is a 5 ton, 10hp motor. All our hoists use drive specifically designed for hoists, with encoder feedback to detect movement can corrections.

Issues I see:

1.) Is there a mechanical load brake or just a motor brake? If just a motor brake, then you can have an issue of load coasting before the current builds up to actually move the load.

2.) Crane De-Rating, If the crane's capacity is 3500Lbs, it needs to be able to lift that. If something ever goes wrong and there is any kind of investigation, you can be held liable for modifications.

3.) Emergency situations: You are going to have to wire this thing in such a way that if there is a failure, the brake locks.

Created Date: July 05,2016

Created by: jwbaker3

As stated by depp6ixed cranes carry a huge liability.

We use Magnetek drives on the hoist motors. They are they are built by Yaskawa but have special software for hoist control (built for this service). You will have to derate the drive to use single phase input, but your local crane guys can help with that.

As the other posters stated beware of the brake, and make sure you derate the hoist by plainly marking the unit with the new load rating so it can be seen from the ground and put the load rating on the hook lift block.

If one of the crane control companies do not offer a single to 3 phase option I would resell the hoist you have and buy a single phase powered unit. A 1/4 ton unit is not that high. (cheaper than the Dr. bills, law suites and fines) We do a lot of single to 3 phase jobs, some over 200 hp (mostly water pumping for farms where there is no 3 phase) We use a 3 phase unit and derate it per Yaskawa's single phase chart.

JW