Can use Soft starter for Construction hoist?

Hi everyone.

Now I have problem with construction hoist (lift material and people for building)

All of hoist use direct on line (DOL) starter method so they are too shock when up or down and reducer are broken after short time operating.

Now I want to use Solf Starter for hoist (it is cheaper than inverter).

Can I use Solf Starter for contruction hoist? If can, what type of Soft Starter I can use for it?

Spec:
- start and stop several thousand times/day.
- Lift people and material (safety first)

Thank a lot!

To me it sounds like a bad idea. I'd go for a VSD.
You'll want as much torque as possible during startup and run. The netto load is probably bidirective also (weight/counterweight). So what happens when you start with a negative load and a very redused torque?


Here is the softstarter handbook from ABB:
http://www05.abb.com/global/scot/scot209.nsf/veritydisplay/2985284834bcff7fc1256f3a00274038/$file/1sfc132002m0201.pdf


Kalle

There are 2 issues to contend with on a hoist when using a variable speed drive or a soft start.

First issue is control of the motor brake.

The second is dissipation of regenerated energy by the motor. This occurs when the motor has to hold back the load. This is during lowering if the load is not counterbalanced, or can be during lifting or lowering if the load is counterbalanced, depending upon whether the counterbalance is lighter or heavier than the load.

In my opinion the best option for you is to use an inverter instead of a soft start and the inverter I would suggest is the Schneider Altivar 71. This is a more expensive option than a soft start, but is a much safer one, so the bean counters have to take a back seat on this one.

The motor brake will have to be separately wired, and controlled by the inverter.
The Altivar 71 has a relay output to control your brake contractor.
This relay has brake logic control, which monitors the following:

1. The inverter output frequency
2. The current absorption of the motor

There are timing functions also with these to further fine tune your brake.

In operation the inverter will detect the motor taking up the load before the brake releases, and then allow the motor to ramp up to speed.

The issue of regeneration causes the inverter DC bus voltage to increase to a level that will cause the inverter to shut down to protect itself. This issue is resolved by the fitting of a braking resistor to the inverter. The specification of this braking resistor will depend on the size of the motor and it's duty cycles.

I have done many projects where hoisting or hoist control was part of the scope and I have used many types of inverters to do this, and have found the Schneider or Telemecanique units to have the best control, and also they can supply the braking resistors.

I have automated hoists and cranes up to 110Kw.

As a footnote, I do not have any commercial connection with Schneider, my suggestions are based on my experience.
I am sure other member have their preference for brands.

BAD BAD when lowering you will brake on the mechanical brake, very bad, if field is lost the lift will fall down.
No braking resistor in a softstarter.
In cranes the mechanical brake is apart from motor, in this cheap hoists, it is the rotor that moves.
your hoist will not meet the requirements anymore.

mindtool said:

Hi everyone.

Now I have problem with construction hoist (lift material and people for building)

All of hoist use direct on line (DOL) starter method so they are too shock when up or down and reducer are broken after short time operating.

Now I want to use Solf Starter for hoist (it is cheaper than inverter).

Can I use Solf Starter for contruction hoist? If can, what type of Soft Starter I can use for it?

Spec:
- start and stop several thousand times/day.
- Lift people and material (safety first)

Thank a lot!

Click to expand...

Most (if not all) soft starters I've used didn't allow more than a couple of restarts per hour.

Thank all for sharing your experience

If not use inverter, could you show me the way how to reduce shock event with low cost.

Spec:
Power: 3 motor x 11kw
1 speed

I worry about torque at start time, not enough to lift hoist.