Tapered shaft motors ?

Hi guys, this is not a plc related question, but i thought, someone might be able to help me out.

I was given a project at work;

to install vfd's to one of our 3 ton overheard cranes. using a 2 switch position pendant station. once the button is pressed to the last position it ramps up the speed. then once the button is released back to the 1st sw position it maintants that speed.

i got the design all working great. but once i consulted our crane maintance guy, he said the vfd's were out of the question for these motors, since they were tapered shaft motors. and this crane is over 20 years old.

They still want me to try and figure soemthign out to install vfd's. i spoke with Delta(the vfd manufactures) (they actually build AB's powerflex drives for them, and AB slaps their label on it, that was news to me.)

anyway, they mentioned a vector function and that i could use that for tapered shaft motors.as far as i know, ttapered shaft motors need a high voltage to start off with ? so how would a vfd work with that?
id relaly appriciate it if i got some feed back from anyone on here regardign this. or any info on tapered shaft motors.

i just finished school a few months ago and dont really have alot of expericne or knowledge, more liek a grasshopper , lol

I'd appriciate any feed back..

Keith

I'm missing something or your crane guy is going senile. A taperd shaft has absolutly nothing to do with anything close to being able to use a VFD or not! That's a mechanical trait, what are the electrical, torque and cooling requrements for this motor? Now if it has a tapered drum you may need to take a closer look at the torque requirements, but the shaft is irrelevant.

You might have encountered motors with tapered cone rotors that slip axially along the shaft with an internal brake lining for the cone to engage. Most of these were known as DeMag motors and are unsuitable for variable speed operation.

The problem lied in the fact that line voltage is required to pull the rotor back to magnetic center thus releasing the cone brake.

If, after all, you simply have squirrel cage induction motors with tapered shafts like mill motors are usually made, drives are just fine with them just as RussB said above.

Thank you guys, DickDV's post explains alot.

i guess the only option would be to replace the entire hoist. since, the hoist motor is attached to the gear box, and to find a replacement motor that fit a 20+ year old gear box is not possible( ive done some digging around).

i was actually hired to do the company's plc work. working with the CompactLogix and PV+600. so il be posting more questions in time to come, thanx for the advice.

sinclair_keith said:

using a 2 switch position pendant station. once the button is pressed to the last position it ramps up the speed. then once the button is released back to the 1st sw position it maintants that speed.

Click to expand...

Huh. You don't have to keep a button pressed in to keep the crane moving ? That's crazy.

my appologies, i didnt explain it too well. technically the switch has 3 states,

1- resting
2- SW1
3- SW2

once the button is pushed to SW2, and held down, it cranks up the freq, then once released to SW1 it holds that selected speed, and thenone the push button is totally released the freq goes back to zero.

decelaration depends breaks and or vfd programmed decel time.

FYI: if initially SW1 is pressed from rest. the vfd does not do anything.

It worked beautifully on the test bench. the 20+ year old crane motor, put a hault on the project.

theDave2 said:

Huh. You don't have to keep a button pressed in to keep the crane moving ? That's crazy.

Click to expand...

No, it is a two position momentary pushbutton.

They are common on crane control pendants, usually switching between two speeds. Push halfway down for slow, and push fully down for fast.

The idea of using the 2nd position as accelerate and the first as hold is a novel one. I will have to rememeber that and try it out someday.

Also, I had never heard of a tapered rotor motor til today...always learning...thanks...

FYI, OkiePC:

the vfd i used was from delta, B series. it had an acc/decc dissable input, which is what i used for SW pos 1. it took me a while to figure out, what vfd's to use, from all the ones i came across, this was the only one that had the Mi6 dissable option. the rest of the suppliers didnt even know what i was talking about.