VFD Winching Application

[nrsoccer]

Looking for some input on the the need for Braking resistors. The application in winching. in some cases it is Material handling from above lifting stopping lowering of load, the other application is for marine winching, vessel moving paying out a load and then retrieval. My thought is that we are "motoring" out the load there is no free wheel of the motor to regen power back to the vfd and when the load is released it is held in place by mechanical braking .Another note the loads are always through gearboxes as well which would further reduce the chance of the load overspeeding the motor to create regen. Thoughts?

 

[itsmoked]

Remember that if you do get regen and there is no place for it to go the VFD will trip off leaving you with NO control. It's probably prudent to use some barking resistor. Build it expecting a resistor and test it without if you must.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[MikeHalloran]

>>>through gearboxes as well which would further reduce the chance of the load overspeeding the motor<<<

Not true for spur or helical gearboxes, which are used for efficiency reasons.
Sometimes true, but not guaranteed, for worm gear boxes.



Mike Halloran
Pembroke Pines, FL, USA

 

[BrianE22]

We use some worm gear winches in our factory. The brake resistor (dynamic braking) gets quite hot when decelerating a load that is being lowered.

 

[jraef]

You need the "barking" resistors regardless of the type of gear drive. In order for you to release the holding brake, you are energixing the motor. As soon as you do, it has the possibility of regenerating. When you give a "Lower" command, even though you look at it as if you are motoring to pay out, from a load perspective it is attempting to fall, it now has kinetic energy. The motor and gearbox is preventing that fall by converting the kinetic energy to heat, as in friction in the gearbox, and electrical energy (regen) in the motor. As itsmoked said, if there is nowhere for the kinetic energy in the motor to go, the VFD has no choice but to turn off, which will set your brake again. If your gearbox ratio is so high that ALL of the load kinetic enegy can be absorbed by the gear friction and stress, then maybe you don't need the barking resistors. I wouldn't design for that.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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[itsmoked]

I hope someday to see barking resistors.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

The motor isn't in motoring mode if the load is trying to pull the motor faster than it is running. This would typically happen when paying out cable while the load is pulling on the cable. If you decide to try and run a winch without resistors then leave room for the resistors unless you like to have your applications fail.

 

[waross]

They LOOK the same Keith.
They do SOUND different when they fail.
I'll finish my first coffee now.
Grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

They will only bark when there is a CATastrophic failure though.