Choosing motors for crane application

[Denimkd]

Hi to all,
I´m new in this forum so please be gentle with me
I have a little problem, so if you can help me with my choise.
I have to choose motors for crane aplication. Old motors are slipring motors. I will put drive for control too.
1. If I choose squrrel cage motors, should I predict to be 30% bigger motors then slipring? I know that Tm/Tn of squerrel cage motors are much smaller then Tm/Tn on slipring motors.I don´t know how to calculate Tstart, and wich motors have biger Tstart.
2. If I choose to keep the slipring motors, and to shortcircuit the rotor (to put out the resistors), how then is going to be the torque of the motor? Is it going to be smaller then beffore, and how much? How can I calculate this?

Can someone advice me what to do?
Thanks

 

[niallnz]

The usual issue with retaining WRIM is can they handle the voltage spikes in the output waveform of the VSD. It is normal practice to put a sine filter on the output of the VSD, which adds cost to the project, and you're still left with your old motors that you think are on there way out any way.

From the basic information you've provided on your crane I think you could do a direct replacement of your motors with equivalent kW induction motors. Force cool the motors and use encoder feedback, especially on the hoist, travel is a bit more forgiving. Do use a VSD with crane functionality built in; it'll make you life much easier. I've used the ABB ACS800 crane drives they are very good. Also use line regenerative VSD's (active front end), they cost a bit more but the saving in mucking around with brake choppers and resistors is worth it, three phase in three phase out, job done.

Cheers Niallnz

 

[Skogsgurra]

Hmm..

"If you want to use a standard induction motor, you will need a VFD and an encoder on the motor. You will also need to use a VFD with a built-in hoist application. It takes lots of trial-and-error before you get good performance from VFD that doesn't have that built in."

That answer, given 15 Jul 11 9:11, was turned down completely as "not what I asked for". Would it be OK now?



Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[Denimkd]

Thanks guys, for your help.
I have decided, I will put drive with induction motors and encoders on hoist.

Now I just have to calculate the size of the new motors and drives and after to try the application.


Thank you very much to all of you.

PS
Gunnar you have to be more relax, not everyone is claver like you)

Best regards

 

[Skogsgurra]

I am not claver! I am grumpy. I do not even know the meaning of claver.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[LionelHutz]

Now, I think I screwed up my last answer and was right with the first thing I posted. I believe the force in Newtons really is like this;
= kg x 9.8 + kg x m/s^2

The calculation give the static force due to gravity plus the acceleration force required to make the load go up. Once you have to force you can calculate the torque back to the motor.

Gunner - I seem to recall questions about the torque the different motors can produce, not the type of drive to use.

 

[Denimkd]

Yes Lionel,

every time I was asking how to calculete the torque of these motors (slip ring and squerrel cage) and will these squerrel cage motors provide me enough torque as slip rings motors.

But how ever, it is very nice for me to include on this forum, there is everytime some action

Regards

 

[electricpete]

there were a variety of questions, not just one. Looks like all good input from my uneducated (cranewise) viewpoint.

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(2B)+(2B)' ?