Best way to control speed of lift application motor?

We are developing a material handling system with a 15hp
lift motor. The mechanical engineers suggest using a 2 or 3 speed motor as in a standard hoist. In the past we have used a Siemens Masterdrive VFD with a large braking resistor. We are trying to develop a cost effective solution, can anyone give some reasons for using or not using a two speed motor or recommend a solution. Can a soft shift controller be combined with a 2 speed motor?

Thanks

 

[cbarn24050]

Hi, there is no reason why you cannot use 2 or 3 speed motors as long as you can tolerate the current surges and mechanical shocks to the system.Ive never heard of a soft shift controller. Some years ago I used to use thyristor controllers on cranes and passenger lifts (elevators) but they are now unpopular due to harmonic distortion and emc regulations here in europe.

 

[SteveKW]

Take a close look at the expense of a two speed motor first. Also find out what happens to the HP when changing from one speed to another.

 

[jbartos]

Suggestion. A gear box with a single speed motor and a remotely controlled gear could be also given some considerations.

 

[rodar]

Try to find what is called a
REGENERATIVE variable speed drive.
I know MITSUBISHI makes one.
It puts the extra power back
onto the grid.
Enviromentally friendly that way.

 

[GSI1]

The answer to your question I simple use an Electromotive Systems Flux Vector Hoist Inverter. To make it short with this motor controller combination you can control the speed of the load from 0 to 2X the motor full speed with 150% torque. With their eye for safety the shaft brake is checked both before and after each pick. In addition you have the ability to suspend the load on just the motor for long periods of time.
I have install these on cranes for years and they work great.
If you need help I can supply with a complete system.

 

[jbartos]

Suggestion: A small addition to the above two postings. The regenerative inverters come with Active Front End (AFE) that has a small harmonic distortion on its input side. Therefore, the harmonic concern is somewhat diminished to a negligible amount. See for example:

http://www.siemens.de

for Simovert

http://www.baldor.com

for 22H series motor drives
etc.