19 years ago
A good friend is trying to start a small garage service going to service and
restore old cars.
He picked up a 2500 Kg two poster car lift from the adds and installed it.
At the same time the Electric supply company was approached and survey and
price sought to supply 3 phase to the garage to deal with the various things
he would need.
The price that came back to him was over £9,000 plus VAT. Now whilst that
may not seem a lot to some people, it is a bloody great deal when starting
and needs a lot of through put before that sort of price can be justified.
It seems there is a general problem in the area, of the transformer being
under rated for the surrounding houses and farms and the price included part
charge for new transformer of larger capacity!
So I though I would let him use my static converter 240 in 415 out at up to
It crippled the mains when we tried to start up the 4 HP motor on the ramp
even without a car in place.
The mains input dropped to around 180 Volts to the static inverter. Larger
cable is going to be fitted to help minimise the volts drop taken from the
household supply, but the fears are that even this will not solve the issue.
I have been thinking of reducing the ramp motor from 4 HP at three phase to
2 HP and going to Single phase supply, The start-up currents would be
reduced and hopefully less chance of taking the supply down.
Now as it stands the 4 HP motor is 3 phase, runs at 1415 rpm uses pulleys to
reduce speed 70 cm and 230 cm so around 1/3 reduction in speed and the lift
screws are 5 TPI.
So my basic working out gives me 1415 * 70/230 = 430 rpm screw speed
430 rpm / 5 TPI = 86 Inch lift a minute or around 7 foot lift in a minute
which I guess is about right.
Now going down to a 2 HP motor would I need to need to reduce the lift speed
by 2 by changing the motor reduction by 6 to 1 instead of the 3 to 1 now in
use. Assuming same rpm motor.
Or would I in fact have to go even higher in reduction due to using a single
phase motor that has lower starting torque then a 3 phase 2 HP motor.
say to 7:1 reduction from the 3:1 reduction now in use.
Any advice from those in the know is very much appreciated especially from
anyone else that has done a similar change.