Three Phase Single Post Car Lift

[Joe Malone]

Hi all,

I'd appreciate some general advice around installing a three phase car lift into my garage at home.

My house was fully rewired to 17th Edition about 3 years ago. The garage wasn't wired up because I knew I'd be building a much bigger garage. Anyway this is nearing completion bar the new roof and I'm starting to think about electrics.
When the house was wired I asked the electricians to install a circuit for the garage which they have done and I'm currently running a double external socket on this circuit. The intention was to tap in at this point to run the SWA to the garage. The garage circuit is protected by a B20 MCB and I'm unsure if this will be rated high enough, possibly needs changing for a B32?
I have a small dilemma with the lift in that it runs off a 1.5kw 3 phase motor. I intend to either have an inverter installed or change the motor for a single phase. At this point I'm erring on the side of the inverter.
I'd be grateful if someone could just give me an overview on how they see this being wired up? I'll obviously also be installing lighting and sockets aside from wiring up the car lift. This is a full size professional garage lift and obviously I'm a little concerned about the loads on motor start up.

 

[RF Lighting]

You just need an inverter sized to suit the motor.

How big is the existing cable to the garage, and how long is the run?

What else will you be using in the garage? Is it going to be a fully equipped car garage?

 

[AdrianUK]

Also, Can the motor be reconfigured for 220V 3 phase?

(Any inverter that you buy and run off 230V single phase will deliver 230V three phase output... it wont deliver 400V three phase).

If the motor is below about 7Kw then you can often reconfigure it from 400V STAR to 230V DELTA and it'll work fine off the inverter.

Adrian

edit: Your motor is 1.5kW. Most small 1.5kW motors that Ive seen can be reconfigured into delta so should be OK. What might be more fun, in a domestic, is getting the inverter & any RCD to play nicely together - the earth leakage due to the filters on the front end of the inverters tend to make a 30mA RCD a little....trigger happy!!

 

[RF Lighting]

Why would it need an RCD?

 

[Joe Malone]

Also, Can the motor be reconfigured for 220V 3 phase?

(Any inverter that you buy and run off 230V single phase will deliver 230V three phase output... it wont deliver 400V three phase).

If the motor is below about 7Kw then you can often reconfigure it from 400V STAR to 230V DELTA and it'll work fine off the inverter.

Adrian

edit: Your motor is 1.5kW. Most small 1.5kW motors that Ive seen can be reconfigured into delta so should be OK.

Thanks Adrian. That was not a problem I even knew I had, the motor is 3 phase, 380v 50hz. I wasn't really enquiring about the inverter but it sounds like a good job you mentioned it. I've no idea what converting the motor to 230v delta is or how to do it. Can you elaborate please?
That may well be the factor that makes me switch towards buying a single phase motor if it becomes too problematic. Inverters ain't cheap anyway so it was a close call on costs between the two options.
In the main I was enquiring as to what needed installing for the garage supply. The distance between the house and the garage is only 5mtrs and I'm running in 2.5mm SWA cable between the house and garage. The existing house circuit for the garage is in 2.5mm T&E. As I said there is a B20 MCB on the garage circuit at the main CU and I wondered if this was rated too low?
If every other respect this is a standard home garage set up, though a little more serious than most home garage set ups. I do intend to install a compressor but nothing that will put a large draw on the supply.
I'm a surveyor and I manage millions of pounds worth of maintenance work very year so I know more than most non-electricians about electrics, however if you start getting very technical and talking about electrical theory then you will lose me.

 

[AdrianUK]

Why would it need an RCD?

Agreed. The inverter may not...but we don't know a lot about the rest of the setup.... and often domestics have an RCD, especially on the garage sub main

 

[AdrianUK]

Until you have selected a possible inverter & check the instructions (hopefully online) its hard to say if the B20 will be OK.... it might, or it might randomly trip on power up of the inverter. (My gut feeling is it will be OK). In my 'day job' we run 1.5kw inverters off 13A sockets with no real problems other than the tripping of RCDs.

Changing from star to delta - if you look inside the terminal box of the motor you will see, hopefully, six wires each terminated on a post. These are the six ends of the three windings. They should be labelled V1, V2, U1, U2, W1, W2. You'll probably see two bridging strips joining V2, U2 & W2 together - if so then the winding is in star. If you rearrange the strips so that U2 connects to V1, V2 connects to W1 & W2 connects to U1 then the motor will be in delta...


Alternatively, post us a picture of the motor rating plate & the view inside the terminal box.....

Edit..... like wot he says below !!!

 

[matt1e]

Thanks Adrian. That was not a problem I even knew I had, the motor is 3 phase, 380v 50hz. I wasn't really enquiring about the inverter but it sounds like a good job you mentioned it. I've no idea what converting the motor to 230v delta is or how to do it. Can you elaborate please?

It should tell you the voltage ratings on the motor plate yours should have something like 220/380 on it
Take off the motor terminal cover. you should see something like this

the above shows a star configuration and if yours is set for 3ph 380 is how yours should look

to convert to delta remove the three links (it looks as though there are only two but there should be three when you take them off ) and rearange them to a 220 delta config as below

you will have to program the inverter with the delta ratings that will also be on the motor plate

Matt

 

[Joe Malone]

Thanks very much for the advice everyone. I have seen the lift when I paid for it but its not been delivered yet so I can't have a look in the terminal box. If I struggle I may post a picture when it gets delivers in a couple of weeks.

 

[jamesmcbride]

I use an inverter in my garage to run a tyre fitting machine. It works really well, in some ways better than the intended three phase operation, because you can control the speed, direction and acceleration of the motor through the inverter (via external controls).

Mine runs off a B16 RCBO without any problems.

 

[ericmark]

I would think using a single phase motor may present it's own problems. In general with three phase we need to reduce start torque and with single phase we need to increase start torque so the start load is important. Often with single phase the motor is started with no load and the load is only put on the motor once it has reached running speed. This is also done with some three phase systems with items like by-pass valves but not always.

The inverter can be set so the start load is more even than with any single phase motor so it will be less likely to trip out any supply.

As already stated small motors can normally be set 230 or 400 volt where larger motors are 400 or 690 volt so they can be started in the 690 volt mode with the 400 volt supply until up to speed then swapped to 400 volt mode so reducing start current and torque. Referred to as star/delta starting.

Auto transformers can lift the voltage from 230 to 400 and can be built into the inverter so if the motor is the higher voltage type you can still get an inverter but it will cost more.

 

[ricicle]

If this is a hydraulic lift, the motor will usually be started off load anyway, with the hydraulic pressure only being brought on by the control valve once the motor speed is established.

 

[ericmark]

If this is a hydraulic lift, the motor will usually be started off load anyway, with the hydraulic pressure only being brought on by the control valve once the motor speed is established.

In the main I would agree, but everything forward and trust to the lord is not really the best approach. I have seen where the operation of up has a set delay between switching on motor and hydraulics being activated and the increased delay in getting motor to full speed could cause a problem.

The guy needs to be aware that it may not be a simple motor change.

 

[SimonH2]

If this is a hydraulic lift, the motor will usually be started off load anyway, with the hydraulic pressure only being brought on by the control valve once the motor speed is established.

Not the ones I'm familiar with. They tend to have a manual dump valve that lets oil out (lower the lift), and the pump that puts oil in (raise the lift). Unless the lift has been lowered onto the safety catches or the vehicle is on the ground, then it'll start under full load.

Starting a tyre machine is a different matter - not a lot of starting load. I'd expect significant problems with a lift. I know at my mates workshop he had a 32A supply for it (his was single phase). It burnt out the pathetically small relay it was fitted with, and I fitted a "proper" contactor instead.

I'd suggest the OP investigate having a better supply to the garage. Ideal might be to split off the tails with a switch-fuse or see what size breaker he can get in the CU - preferably not RCD protected. Then install a small Cu in the garage.
This means the garage lights won't go out if the ring final trips, and things are close to hand to reset.

As to running this motor, there are static converters (not inverters) which are basically a step up transformer and some caps to generate 415V and a 3rd phase. One of these, plug perhaps a small motor to assist the phase balancing would do the job.
Single phase motor is by far the simplest option though.