Motor speed controller.

[Rampage]

I have a milling machine that has too high a motor speed.
If I use a speed controller does that reduce the power output from it as well as the speed?

It is a 0.5hp 3 phase motor.

Also, where's the best Alsace to get one?

 

[Marvo]

0.5 hp is a very small motor, check the info plate, it may be able to run in star as well as delta, this would reduce the speed somewhat. Otherwise a VFD would be the answer, it would maintain full flux saturation even at lower speeds so the torque should be close to the maximum. Problem is that a VFD will probably cost 2 or 3 times the price of the motor so maybe look at a 6 pole replacement if the existing motor is 4 pole.

As for where you can get one, there's no shortage of suppliers, even your local electrical wholesaler should be able to supply VFD's.

*edit*, another option might be to reduce the pulley wheel size on the motor if it's belt driven, or increase the pulley size on the driven end.

 

[Darkwood]

0.5 HP what you spinning on it Candy floss!

 

[Rampage]

Thanks for that, I think I remember it saying it could be run in star now you mention it.
The actual mill has a 3hp motor, when I bought it it only had the high speed head on it, the standard head is powered by the main motor.
I think the high speed head will be ok for what I want it for, just a bit too fast!

 

[Marvo]

Is it belt driven or direct drive?

 

[DPG]

Alsace??? Daz

 

[Marvo]

It's a region in France famous for the manufacturing of under powered but very fast milling machinery.

 

[DPG]

The missus is now wondering why I'm chuckling! :teeth_smile: Daz

 

[Rampage]

lol
It's belt driven, due to the housing there isn't really enough room to make the larger pulley any bigger. The smallest pulley looks like it's the minimum size for the belt as well. I could add another two pulleys on a new shaft, inbetween the other two pulleys (compound pulley system), but again, probably not enough room.
I'd rather adjust the speed electronically to save time etc.

Its an Aciera F3

 

[Marvo]

Is the smaller pulley or the larger pulley on the motor?

 

[Rampage]

There is a stack of 4 pulleys on both the motor and driven end, the current slowest speed is achieved with the belt on the smallest motor pulley and largest driven pulley.
This makes it 1000 rpm, I would like to make it adjustable from 125 - 1000 rpm.

 

[Rampage]

This is the head thats on it.

 

[Marvo]

Even with a VFD you're not going to be able to achieve 125RPM safely, we generally draw the line at 33% of full speed with a TEFC motor because it overheats with the slower cooling fan speeds. At 12.5% of full speed you're going to have problems, much lower than 33% you'll need to put an independent electric fan on the back of the motor and the expense starts getting out of hand.

Why do you need such low cutting speeds? Is your material really that hard or are you using large diameter tooling?

 

[Rampage]

I do cut titanium and hardened steel from time to time. Mainly HE30 Aluminium though, so higher speeds would be used the most.
I will see if it can be wired as star when I get home.
What would you estimate that would reduce the speed by?
Thanks for your help

 

[Marvo]

Just check if the motor is capable first. It will have reduced torque and depending on load you may end up with the motor in stall. From the info you've given I'd be tempted to rather go with a VFD and settle for 330RPM as your lowest speed. If the motor has a built-in thermistor make sure you wire it back to the drive to give some protection should it overheat at the lower speeds.