Clutch Puley?

benha · Jan 29, 2021

Howdy!

I'm commissioning a new-to-me wide belt sander. It's been an adventure all the way 'round, but I'm nearing the finish line. I've got one last hurdle though:

This is a two-headed machine. One head has a 17HP motor, the other is a 30HP. The 30HP motor's startup load is more than my electrical service can handle. Its oh-so-close, but it trips the breaker.

When I remove the v-belts connecting the motor to the drive drum for the sanding belt it starts up no problem, though!

I'm wondering if there's a "proven" way to get the motor spinning before engaging the sanding head, perhaps via an electromagnetic or centrifugal clutch system? Could also be other mechanisms I'm not considering... If I can separate the inrush load from the drum-start inertia load I'll probably be in clover.

The other option is, of course, to replace the 30HP motor with a smaller one, but I'm hoping to avoid that.

Oh, and this is a machine of European descent so the motor shaft is 42mm, which seems uncommon.

Metalurgent · Jan 29, 2021

Look into Star-Delta contactors as a possible solution for the larger motor assuming its a 3-phase machine.

M. Moore · Jan 30, 2021

I think you need to talk to an electrician? If the motor trips the breaker then something is not sized correctly for the load or you are not explaining the problem well enough.
A breaker capable of starting a 30hp motor should be able to handle the inrush current.
I am not an electrician but have over 30 machines in my shop and most of those I installed myself. (because I had no choice) Now I use a local electrician and he has been great to work with and I highly recommend you to use a good electrician that understands industrial machinery installations.

Good luck,
Michael

stephen thomas · Jan 30, 2021

By inference (yeah, know how tha goes

) i think he is saying the service entrance or branch service is at its limit/panel breaker sized accordingly?

I documented my experiences with similar situation on here many years ago. When we moved here in ‘93 I upgraded the house service entrance from a couple pull fuses (60A total) to a regular 200A panel. Then took 125A branch straight to the shop. NYSEG inspected and agreed to the modernization, hooked up to the service entrance, and adjusted our monthly bill to reflect.

A few years after that i installed a Ramco sander that came from one of PM’r Surplus John’s auctions ith a 30 HP motor. It blew the pole pig a couple times before the power company came out and instrumented our house & shop for a month. The upshot was that they had never upgraded the transformer on the pole to actual 200A capacity.

However, in the meantime i simply replaced the 30HP with a 15HP since that is still a bit more than my converter is actually rated. Surplus 3ph motors are pretty cheap depending on local second/third hand resources & scrappers.

smt

benha · Jan 30, 2021

I’m at the limits of the service. Correct.

I don’t have 3Ph to the shop so I have a 50 HP phase converter. The circuit protection is correct, it’s just the combined inrush-under-load effect puts it just over the line.

I could replace the motor, yes, but hoping not to have to. It’s a bit more complicated (though certainly manageable so) because it’s a 3600rpm European motor with a 42mm shaft. Not gonna find one of those used. So I’d need to find all the right bits to convert to a 1-5/8” shaft motor. Was hoping someone might have an easier (cheaper) idea.

Sent from my iPhone using Tapatalk

richard newman · Jan 30, 2021

What about using a vfd to get a soft start? Not sure exactly how it works, but I think it helps to avoid that huge inrush.

I had a similar situation 35 yrs with a 5hp 36" Tannewitz bandsaw. The electricians measured the current spike at 80 amps! They wound up using some sort of time delayed breaker, allowed enuf time for the spike to pass. Sorry I can't be more specific, but no doubt someone else can. I'd post this on the General forum, or Transformers, Phase Converters, VFD forum

M. Moore · Jan 30, 2021

Did you try running the smaller motor and then starting the larger one? Or is it an either or situation?
When I used to run my converter the sander had an amp meter and the more motors running ( other machines) the less amps showed on the meter.

macgyver · Jan 30, 2021

Only inexpensive thing I can think of is to put an idler inline with your drive belts that you can engage with a handle like a clutch. Look at old line shaft drive machines and setups for pics. My Delta RC51 planer has a similar setup for the power feed engagement.

Anything else I think will get in the realm of cost of a new motor. Have you priced a new motor? It may not be as bad as you think and would bolt in.

Soft start for 30hp might be affordable: first one on google; http://www.gohz.com/30hp-soft-starter

richard newman · Jan 30, 2021

macgyver said:
Soft start for 30hp might be affordable: first one on google; 30 hp (22 kW) Soft starter, 220v/440v/480v/690v | GoHz.com

from that link: "The only other reason to choose a VFD over a soft starter is to reduce the start current considerably. This can be of value where there is a very limited power supply."

Might be worth calling them to get clarification on that.

atomarc · Jan 30, 2021

In regards to your 42mm motor shaft. Typically, a sander that large would use a multi-belt sheave and that sheave would have some sort of taper lock bushing to fit the motor. There are off the shelf bushings in all styles that come in metric bores to fit the sheave you have. Have you researched this?

Stuart

Strostkovy · Jan 30, 2021

I rigged an idler motor that could get it up to speed so I could then turn on the 30hp motor. The project failed for unrelated reasons.

Shaybuilder · Jan 30, 2021

we used to use some fluid couplings on our 250 HP centrifuges which allowed slip until everything came up to speed. Not sure of the make anymore but they weren't cheap.

richard newman · Jan 31, 2021

Strostkovy said:
I rigged an idler motor that could get it up to speed so I could then turn on the 30hp motor. The project failed for unrelated reasons.

This sounds like the winner to me! Wonder how large a motor it would take, and how fast you'd need to spin it to make it work for you? Probably could measure the torque required to get it moving with a torque wrench or lever with weight on it attached somewhere.

atomarc · Jan 31, 2021

richard newman said:
This sounds like the winner to me! Wonder how large a motor it would take, and how fast you'd need to spin it to make it work for you? Probably could measure the torque required to get it moving with a torque wrench or lever with weight on it attached somewhere.

We (company) had a 52" Timesaver with electronic tracking which was active even when the head was OFF. If contemplating the idler motor starting scheme, make sure whatever tracking system is ON even with the head OFF as the idler brings it up to speed...otherwise your heading up that creek..sans paddle.

Stuart

Strostkovy · Jan 31, 2021

richard newman said:
This sounds like the winner to me! Wonder how large a motor it would take, and how fast you'd need to spin it to make it work for you? Probably could measure the torque required to get it moving with a torque wrench or lever with weight on it attached somewhere.

I think a 5hp compressor motor would be fine. I didn't bother disengaging it, as it's not an issue spinning a motor after you cut power. Torque required definitely goes up as it gets faster.

My setup never got running because the 40hp idler motor on the phase converter was a dead short and it took me too long to realize it. I got burned out on the project and then we moved to a shop with 1200 amps of 3 phase, so it was no longer needed.

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