3 phase inverter ?

[makeitfit]

Hi learned ones who do elektrickery magic .
I need help working out what 3 phase inverter I need for my 4 post lift. We've only got ordinary 240 in the barn.
I've seen many online but came to realise I don't know what to get ?
This the label on the motor

[rustic]

For most 3 phase motors of a particular frame size, there could be a single phase equivilent, but that is quite a big motor.

Another alternative, is a motor gen set, 240 volt single phase motor driving a three phase generator/ alternator.

For an inverter, you would need quite a powerful one to drive an inductive load of an electric motor. I would guess Rick would offer some advice on that.

[solarman216]

The plate says 220 delta 380-420 star so I am guessing it could be converted, but may well be wrong on that, but in any event it is not a large motor at 1500 watts so you can use any 230v motor at 2850 revs at 1500 watts, forget inverters for this they are a no go, you could use a phase converter but cost will be much more than a new motor at 230v, Rick

[glanrichbex]

There are a few conciderations

Is this motor required to run in both directions? In three phase it is done by swapping two of the phases. In single phase it's a bit more difficult.... but it can be done.

or

Does this motor run a hydraulic pump? this only requires it to run in one direction.

Is this motor required to start under load?


It would probably need to be a 4 pole single phase induction motor. When we look at a single phase motor, it is a really a three phase motor but it uses capacitors to derive the other two phases by utilising the phase shift phenomena of a capacitor.

The problem with this method is that it is not very efficient compared to a three phase motor. The power factor is only 0.7 e.g a 4KW single phase induction motor actually consumes 5.6KW

They also do not like starting under load, it may run all day at it's maximum load rating but getting it there is another problem.

When a motor starts, it can draw up to 6 times its running current until it gets up to speed. This will eventually knock out your main fuse which will take some explaining to your electricity provider.

To start a single phase motor successfully you need a softstart unit, like a Fairchild HFE2. This will analyse the current drawn by the motor and limit the voltage in sympathy to the rotation speed and dramatically reduce the start up current .

There doesn't seem to be many manufactures making soft start units for single phase motors above 3KW.

The other alternative is an inverter starter, this means you do not have to change your motor, it's a box which goes between the supply and motor. It's more expensive than a soft starter but by the time you've changed the motor and bought a soft starter, you would probably find it's cheaper to buy just the inverter.

[solarman216]

My two post lift runs on 13 amp plug no problem all all and lifts 3.5 tonnes, Rick

[glanrichbex]

Originally Posted by solarman216

My two post lift runs on 13 amp plug no problem all all and lifts 3.5 tonnes, Rick

No doubt - but every time for that split second your starting it, your chipping a little bit at a time out of your main fuse, and one day it will be the straw that breaks the camels back. It's not good for the motor windings or mechanical components of an induction motor to start direct on line due to the load current and the sheer mechanical shock. It's always better to soft start a motor rather than presenting a short circuit.

[makeitfit]

I wish I hadn't had the last wine . Not following it all sorry guys.
The lift is a Bradbury 3 tonne 4 poster and has this motor that drives a hydraulic pump. As far as I can tell it drives up and gravity down.
Is this kind of thing any good ?
http://www.ebay.co.uk/itm/1-5kw-2-HP...UAAOSwLVZVkoWg

[rayf3262]

Originally Posted by makeitfit

I wish I hadn't had the last wine . Not following it all sorry guys.
The lift is a Bradbury 3 tonne 4 poster and has this motor that drives a hydraulic pump. As far as I can tell it drives up and gravity down.
Is this kind of thing any good ?
http://www.ebay.co.uk/itm/1-5kw-2-HP...UAAOSwLVZVkoWg

Something of that order is by far and away the simplest route to getting your lift up and running on a single phase supply.

[Terrano Steve]

I am now going through exact same thing I have a 4 post ramp electric / hydraulic & I have bought a motor from SW Motors & Fans Ltd 01460 259937.
The guy seems quite helpful all he needs is details of your 3 phase motor
how it is mounted (flange type)measure across mounting hole centres(pcd) dia of output shaft speed & hp or kw.

[RJL Services]

mine is a bradbury 4 post lift like yours and was once 3 phase and the person i bought it from had a company change the motor to a single phase one as it only lifts and gravity lowers it i will take some pictures of it later today and post tonight but i have had it two years now no problems with the motor at all i will also see if there is a name plate on the motor too

[makeitfit]

Cheers guys. I assume then that these motors can be found to mate up to the pump gizmo
Sounds good to me if that's the case I'll go that route me thinks. One less bit of bolt on stuff in the way
Can't wait for the Black Pearl to be off the drive and up in the air.
Mod list is massive

[glanrichbex]

Originally Posted by makeitfit

I wish I hadn't had the last wine . Not following it all sorry guys.
The lift is a Bradbury 3 tonne 4 poster and has this motor that drives a hydraulic pump. As far as I can tell it drives up and gravity down.
Is this kind of thing any good ?
http://www.ebay.co.uk/itm/1-5kw-2-HP...UAAOSwLVZVkoWg

It would work ...... for a while but you need to invest a bit more and buy a quality unit that will last and has output monitoring and protection. The problem with cheap inverters is poor sine wave simulation which contains a large amount of DC which gives poor efficiency and heats up the windings. Motors take a hammering but abuse to the windings just adds up and doesn't go away when it cools down again. Over time the motor will just fail due to a short between layers of windings and it has to be stripped and rewound.

When the output stages of these cheap inverter units go wrong, quite often it results in a short circuit output FET on one of the phases. This results in the phase being held at 350v DC ( rectified 240v mains input ) which instantly burns out that particular phase winding in the motor.

Have a look at the units in RS and similar distributors, the price may make your eyes water ..... but hopefully it will save you buying another motor and inverter.

[solarman216]

swap the motor Pete for a single phase jobbie, you will find a motor easy enough and inverters of the cheap variety are just not worth the bother and as glanrichbex says a good one to do your job will make your eyes water, incidentally glanrich my hoist was designed to run on a 13 amp supply, and the motor does not start under load, I think the hydraulic pump is pressure relieved once motor stops so when it starts it starts easy, Rick

[makeitfit]

I did come to the conclusion of replacement motor route a few posts back , though not necessarily as a result of full understandingness
I've found a company that says they do a direct replacement motor for the Bradbury, just waiting for tomorrow for real person speaky speaky