car ramp problem ??? anyone help?

[lee mcgregor]

I have a car ramp that is powered from a single phase to 3 phase converter but the ramp struggles to lift anything other than very small cars. Is it possible that the converter is too small for the ramp motor? Here are the details i have on the motor and converter.

Converter:

Input : AC1PH 200-240v 50/60Hz 40A
Output : AC3PH 0-240v 0-400Hz 17.5A 6.7kVA

Motor:

Motor power : 4.kKW
Voltage : 230-400 V 3ph
Absorption : 230V:20.7A
400V:12.0A
Poles : 4

230 delta / 400 star
20.7A delta / 12A star

Thanks

 

[boatnik1]

Certainly looks like the converter? (inverter) is way to low rated for the motor you are driving. The assumption is that you have the motor connected delta and not star.
I presume you don't try to set the Hz above about 60 as that would cause more problems.
If you can't replace the inverter with a larger one, is there a possibility that the output gearing between the motor and the ramp could be changed to allow the motor to run up to speed without needing the motor to need full load amps.

 

[silva.foxx]

Please excuse me... I'm a little naive.

Is this ramp screw-jack or hydraulic?

 

[lee mcgregor]

Its a screw-jack ramp.

 

[boatnik1]

You still haven't let us know what way the motor is connected,
star or delta, but as said before, the inverter is too small and needs replaced or a lower KW motor running tthrough a gearbox would get you the lower current but although the ramp would lift heavier loads it would work slower.
Eitherway, get the hand in the pocket and get out the loot, is the only answer.

 

[montybaber]

Hi there

Am I being dense here, why is the inverter underrated?

Can you confirm whether the motor is connected star or delta

 

[boatnik1]

why is the inverter underrated?

Motor 20.7A at 230v delta 3P
Inverter output 17.5A 0-240v 3P max

 

[montybaber]

Is the motor rated at higher than 4KW? cant get my head round why the current draw is so high (assuming a power factor of 0.8, I know assumptions eh? ) looking back at the post the first k may be a typo on the motor info and there is a decimal point there too

Thanks BoatNik I didnt understand why a vvvf rated at 6.7Kva wouldnt drive a 4kw motor

Sorry prob just being thick lol, wouldnt be the first time!

 

[boatnik1]

Is the motor rated at higher than 4KW? cant get my head round why the current draw is so high (assuming a power factor of 0.8, I know assumptions eh? ) looking back at the post the first k may be a typo on the motor info and there is a decimal point there too

Thanks BoatNik I didnt understand why a vvvf rated at 6.7Kva wouldnt drive a 4kw motor

Sorry prob just being thick lol, wouldnt be the first time!

Guess we can only work with the numbers we are told even if some of them don't sound right.
The Poster said this was a converter and I made the assumption it was an inverter as inverters are usually the ones that give a wide Hz range for speed control. (there's those assumptions again). Since the numbers don't quite tally I was wondering if the motor was connected star or if the Hz was set away above the motor rating which presumably is 50. The given currents for the motor sound about right for 4.4Kw,(maybe that other k is a 4) it's just the output Kva on the inverter/converter or whatever it is sounds a little strange but if the poster wont talk to us, I guess we just wait.

 

[SASCHLO76]

what is star and delta connection ? confused ,com :whatchutalkingabout

 

[Des 56]

They are configurations for 3 phase windings

With motors, they are used to cope with the high starting currents and lower running currents of a motor efficiently

 

[SASCHLO76]

thanks. so how do ya tell

 

[Knobhead]

Delta

View attachment 7398

Star

View attachment 7397

 

[boatnik1]

what is star and delta connection ? confused ,com :whatchutalkingabout

Pic Shows Typical star connected motor for 380-440v 3p with the three power lines going to the lower three terminals.
Delta connections for 220.240v 3p would remove the top links and replace them vertically from the upper to lower terminals
with the power connections remaining as above.