Single to 3 phase converter

[Calebp43]

Been called to help a friend who can't get anyone to look at his car lift until next week and it's stopping him from working. I said I'd have a look but never work with 3 phase converters so I'm not very clued up.
He bought a car lift and it doesn't want to turn on. He saw it working fine before buying it. It's 3 phase. He has a Transwave 240 volt to 415 volt 3KW convertor and its brand new. He thought it was faulty so got it checked and they reassured him that the converter was fine. I tested the outgoings of the converter which is just
L1 L2 L3 and E and I was getting 355v on l1 phase to earth and then the other 2 phases getting 93 volts to earth. 440v from l1-l2 and 440v from l1-l3 but nothing from l2-l3. Is this normal?

 

[James]

https://transwave.co.uk/storage/downloads/9/STC%20Static%20Converter%20Literature%20&%20Manual%202021.pdf

looks like the control circuit must be connected across L1 and L3

try swapping L2 and L3
if it works, great
if it still does nothing swap L1 and L2
if it works with wrong rotation direction, further swap L1 and L3

 

[Julie.]

Been called to help a friend who can't get anyone to look at his car lift until next week and it's stopping him from working. I said I'd have a look but never work with 3 phase converters so I'm not very clued up.
He bought a car lift and it doesn't want to turn on. He saw it working fine before buying it. It's 3 phase. He has a Transwave 240 volt to 415 volt 3KW convertor and its brand new. He thought it was faulty so got it checked and they reassured him that the converter was fine. I tested the outgoings of the converter which is just
L1 L2 L3 and E and I was getting 355v on l1 phase to earth and then the other 2 phases getting 93 volts to earth. 440v from l1-l2 and 440v from l1-l3 but nothing from l2-l3. Is this normal?

If it's a static converter, yes those figures would appear correct, static converters provide the correct voltage over two phases and a phase shift to the third, completely unbalanced and of the wrong phase angles, but they are designed to run a single motor.

Once this motor starts it balances the phases, and you get a set of (roughly) balanced voltages and phase angles.

If it's a rotary converter (basically a static with an integrated pony motor) the phase voltages and angles should be more balanced from the outset. - you can hear the motor running in this type.

With a static, since the voltages are all over the place until the motor is actually running, the connected equipment (car lift in your case) has to be connected such that the control circuit has a valid supply both before and after its running.

Look in the car lift - wherever the control circuit is connected ( red to yellow or blue to neutral or wherever) then these phase(s) need to be connected to the output from the converter which has a suitable voltage prior to the motor running.

 

[mainline]

Been called to help a friend who can't get anyone to look at his car lift until next week and it's stopping him from working. I said I'd have a look but never work with 3 phase converters so I'm not very clued up.
He bought a car lift and it doesn't want to turn on. He saw it working fine before buying it. It's 3 phase. He has a Transwave 240 volt to 415 volt 3KW convertor and its brand new. He thought it was faulty so got it checked and they reassured him that the converter was fine. I tested the outgoings of the converter which is just
L1 L2 L3 and E and I was getting 355v on l1 phase to earth and then the other 2 phases getting 93 volts to earth. 440v from l1-l2 and 440v from l1-l3 but nothing from l2-l3. Is this normal?

The voltages do not relate to earth,
phase to phase readings Should be:
400/420v between L1 and L3
560/580v between L2 and L3
160v between L1 and L2.

I'm assuming the ramp needs 240 for the 24v transformer control side of things, is that there ?

 

[Calebp43]

Thanks for the comments. I will be going back later today to try swapping the cables. Attached is a picture of the lift.

 

[brianmoooore]

It might be an idea to modify the control circuits so that they run directly from the 230V 1Ph supply, and only use the converter for the motor.

 

[Julie.]

It might be an idea to modify the control circuits so that they run directly from the 230V 1Ph supply, and only use the converter for the motor.

I think it is a pure 3 phase lift, as it's rated as 3ph +pe rather than 3ph 4w + pe

I assume the control circuit will have a 400/24V transformer - this must be powered up by being on suitable phase connections - it may currently be between L2 & L3

 

[brianmoooore]

The converter that the OP mentions (assuming it's the 3kW model) is not rated for a single 3kW motor. Max. of 2.2kW.

Transwave Rotary Phase Converter MT3 - 4hp/3kW 240v to 415v

Transwave Rotary Phase Converter MT3 - 4hp/3kW 240v to 415v | Available from Markfield Woodworking Machinery

mwmachinery.co.uk

Possibly an overload protection cutting in?

 

[Calebp43]

I think it is a pure 3 phase lift, as it's rated as 3ph +pe rather than 3ph 4w + pe

I assume the control circuit will have a 400/24V transformer - this must be powered up by being on suitable phase connections - it may currently be between L2 & L3

And what would you say they should be on? L1+L3?
Another thing is that there is a neutral bar in the lift with a cable going to it but apparently it worked before without a neutral. Also that photo doesn't say anything about a neutral.

 

[Calebp43]

https://transwave.co.uk/storage/downloads/9/STC%20Static%20Converter%20Literature%20&%20Manual%202021.pdf

looks like the control circuit must be connected across L1 and L3

try swapping L2 and L3
if it works, great
if it still does nothing swap L1 and L2
if it works with wrong rotation direction, further swap L1 and L3

Tried and no luck

 

[Julie.]

And what would you say they should be on? L1+L3?
Another thing is that there is a neutral bar in the lift with a cable going to it but apparently it worked before without a neutral. Also that photo doesn't say anything about a neutral.

Can't tell from the outside.

The converters have a 230/400V transformer - which may then give one phase to phase voltage say L1- L2, then there are a set of capacitors to generate a phase shift to L3.

If the control circuit is placed across the same phases as the internal transformer in the converter (L1-L2 in the above example) then all is good the control circuit gets a proper voltage.

If it ends up across the capacitor, it is likely to shunt the voltage down to near zero - so no volts on the control circuit.

If it shunts the balance capacitor, the main capacitor may give sufficient throughput to present an odd voltage on the control circuit.

Just swing the phases around, move L1 to L2, L2 to L3, etc, if that doesn't work, do it again.

EDIT

If you are there, internal to the control circuit on the lift, where is it connected to?

It will either be connected phase to phase or phase to neutral.

Those phases are the ones which must be connected to L1 and L3 from the converter (or L1 and neutral from the converter)

 

[mainline]

 

[Lucien Nunes]

That circuit in post 12 shows the control circuit working at 230V from L1 to neutral, whereas the OP says his customer's lift worked in the past without a neutral, which either means:

• His control circuit is different and works at 400V
• His panel contains a 400/230 transformer to achieve the same result
• It had sneakily picked up the earth for the control circuit return as no neutral was available.

I think this needs to be firmly established before experimenting with the converter. Assuming the control circuit is then rigged (with a transformer if necessary) to run between two lines, the above posts esp. No. 11 have all the necessary re picking up the two lines on the converter transformer secondary.

Try to get the rotation correct first time. Some hydraulic pumps don't like running in reverse once they have been used for a while and developed a wear pattern.

 

[Calebp43]

I went there earlier and found that two phases was down when it got to the motor which seemed weird because there was voltage on those phases before that. Turns out the failsafe lead which was connected between the controls and the motor was stuck (must have got damaged in transport). The converter was fine.
Originally I thought that the converter was dodgy due to the weird voltages and it was my first time seeing one. Been a good experience and didn't accept money off him because went there twice and took me a while to figure out because of taking things apart, double/triple checking everything as I was going along due to inexperience with this sorta stuff + was a friend.
Either way I learned a lot on the way and am super greatful to you guys for the help. If anything I've learned a heck of a lot about converters now and know what to look out for next time.
Thanks again

 

[James]

Never hurts to have a mechanic with a car lift owe you a favour!!
well done for finding the fault.