OT: Altivar 31 Torque Boost

I helped a friend setup Tele Altivar 31 over the phone - he need 3 phase in his garage for a car lift and only has single phase at his house.

We got it working - when he lifts a car from the ground it goes all the way to the top and can go back down. But if he wants to go up further when the car is already off the ground then the motor just slips.

Any suggestions on boosting torgue? I have briefly gone through the manual but cannot find a torque boost parameter.

One problem could be that it is a 3kW motor and only 2.3kW drive.

Thanks

Not clear on what you mean by "motor just slips". Is it stalled and cannot develop enough torque to move? If that is true, why doesn't the motor roll backward and lower the car?

I just happened to be in this guy's city today so I stopped by.

The guy made a video of the motor trying to run see http://youtu.be/IuyZaeQemGc

The car lift has wormgears - so even if you disconnect the motor the lift does not drop by it's own.

When the car is lifted off the ground the motor is just stalls when you try to lift it further.

If he starts with the car's wheels on the ground it works fine. The car he is lifting is a full race car so it does not weight much.

First, while a worm gear over 28/1 ratio will lock up if reverse driven, it is not to be trusted from a personal safety perspective. I certainly hope that some other backup method is being used to keep the car from falling.

A wormgear that is locked up by reverse torque is going to be a very hard starting device in the forward direction. If in doubt about this, put a torque wrench on the input shaft when the car is being held up and see how much torque the shaft requires to begin moving.

The maximum torque the motor can produce at stall will be the normal running torque calculated from the motor nameplate data times the ratio of the drive's maximum short-term amps divided by the motor FLA.

If your torque wrench test shows more torque than you just calculated above, you have the explanation for the motor stalling.

The motor itself can produce about double the calculated torque from the motor nameplate from a purely magnetic standpoint. If that is enough to overcome the lockup torque, then a larger VFD with short-term amps about double the motor's FLA will excite the motor adequately to produce the double torque necessary to get restarted.

Please be sure to note my caution about the gearbox-motor-drive system not being a safe system for holding the car up. Adjustable jackpoles or other blocking scheme is essential for protection against a dropped load.

The lift was made in Germany and only has a small brake on the motor to stop the load from dropping. I have seen other lifts that use chains of a hydraulic cylinder with cable to lift - you won't catch me under those.

I think he might have to live with it the way it is now - the biggest 230V single phase drive available here is 2.2kW which is what he has got.

Thanks for the help.

Other brands go much larger. And, you can always use a 230V three phase drive twice as large as you will need and single phase the input. I've done 75hp (100kw) motors single phased when no three phase power is available.

When you use a 400/230 volt motor supplied via a single phase inverter supplied by 230 volts then the motor must be connected in Delta. Has this been done?

Some weird suggestions that may or may not help. Lengthen the Accel and Decel times. Increase the volts per hertz ratio. Decrease the Max Frequency. See DickDV's posts #4 & #6 for the best solutions. I had the exact same problem and doubling the HP size of the VFD Inverter solved it.

Use the ufr function