Mounting an INVERTER

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wally318
Posts: 107
Joined: Sun Jun 05, 2011 1:06 am
Location: Kelowna, British Columbia

Mounting an INVERTER

Post by wally318 » Sun Apr 21, 2019 11:36 pm

Can an inverter be mounted directly to a motor?
On something like a Rockwell vertical mill, where you
might have a drum switch mounted directly to the motor
junction box. Could an inverter be mounted on the same
position?
Is/are there any good reasons not to mount it there?

choprboy
Posts: 224
Joined: Sat Oct 29, 2011 11:23 pm

Re: Mounting an INVERTER

Post by choprboy » Mon Apr 22, 2019 12:18 am

wally318 wrote:
Sun Apr 21, 2019 11:36 pm
Can an inverter be mounted directly to a motor?
On something like a Rockwell vertical mill, where you
might have a drum switch mounted directly to the motor
junction box. Could an inverter be mounted on the same
position?
On the motor.. no, there isn't much structure to mount to. On the machine body, sure why not.
Is/are there any good reasons not to mount it there?
Chips... flying metal chips into the vent holes... Use a full shield, with some sort of cooling solution. Perhaps think about mounting to the back of the column and save the drum switch spot for an on/off/reverse switch to control the VFD.

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rudd
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Location: savannah ga.

Re: Mounting an INVERTER

Post by rudd » Tue Apr 23, 2019 6:09 am

Heat would be another reason not to mount it to a motor. The inverter will likely overheat.

Magicniner
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Joined: Thu May 30, 2013 4:40 am

Re: Mounting an INVERTER

Post by Magicniner » Tue Apr 23, 2019 12:42 pm

Check the manual but most motor frames run cooler than VFD heat sinks so you'd be unlikely to have an issue unless you're running the motor at 80%+ load permanently.
But you'll get two chumps a minute telling you you can or cannot based on absolutely no experience of running this king of kit! :D

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SteveHGraham
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Location: Florida

Re: Mounting an INVERTER

Post by SteveHGraham » Tue Apr 23, 2019 1:19 pm

Latest chump here. A company called KBA or something similar sells dustproof VFD's.
Every hard-fried egg began life sunny-side up.

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rudd
Posts: 647
Joined: Wed Dec 12, 2007 11:21 pm
Location: savannah ga.

Re: Mounting an INVERTER

Post by rudd » Thu Apr 25, 2019 7:09 pm

This chump understands heat transfer calculations. It depends on temperature *difference*, delta T. Deliberately raising the temperature of a heat sink or placing it in a warmer location is not sound practice.
Rig up a remote control, the VFD for my mill lives in a wash-down box up on the wall. The box has a window so I can see the VFD readout if I want to.
At the mill, I have F/R, speed control, a readout of spindle speed (not from the VFD, from a separate inexpensive device that also calculates FPM based on cutter diameter and spindle speed) and a great big red OH S**T button. And a reset for the VFD should I need to hit the big red button.
This is all in a plastic sealed electrical box I got from the big box store, which is mounted about where the original motor control was.

wally318
Posts: 107
Joined: Sun Jun 05, 2011 1:06 am
Location: Kelowna, British Columbia

Re: Mounting an INVERTER

Post by wally318 » Sat Apr 27, 2019 11:28 pm

Hello some of you just can't seem to get the picture.
I just got back from across the border to pick up the
motor/inverter. I stopped at my work shop on the way home
to do a quick mock-up.
So I thought I'd provide a couple pics of my own.
So you can see there's plenty of air space.
Also the inverter is physically high enough that
chips shouldn't get there. But can always silicone
some aluminum window screen over the vents.
What I was really hoping to hear, that none of you
touched on was vibration.
The manual only cautions on punch/shock type vibration.
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shorttrackhack
Posts: 42
Joined: Sun May 15, 2011 4:38 pm
Location: SoCal

Re: Mounting an INVERTER

Post by shorttrackhack » Sun Apr 28, 2019 10:36 am

I thought mount the drive directly on the motor sounded like a good idea. I tested it out on a 24 ft. fan, which blew the diodes right off the circuit board. The magnetic field of an AC induction motor is not an ideal environment for a VFD. Sure, there are those who would argue about installing it in an aluminum box to create a Faraday cage, or other similar types of bandaids. The best advice will come from the VFD manual, use a real motorcable with glands to ground the shielding, protect it in a NEMA enclosure that is sized correctly for the protection level needed for the application (a 4 or 4X rated box will need to be much larger than a 1 or 2 rated enclosure), and have a control circuit with the switches where needed. Mounting in a location like that with no enclosure is asking for trouble, and just plain unsafe.

wally318
Posts: 107
Joined: Sun Jun 05, 2011 1:06 am
Location: Kelowna, British Columbia

Re: Mounting an INVERTER

Post by wally318 » Sun Apr 28, 2019 5:26 pm

I double checked the manual that came with the VFD to see if I missed something.
The only cautions are not to put near something with electo magnetic feilds.
It gave 2 examples: solder machines and power machines. I take it that
power machine means a transformer.
On an induction motor( AC 1 or 3 ph) the electo magnetic feild is focused internally.
If there were an external influence from that feild the motor would shows signs
of becoming an electro magnet. So in a metal shop, steel chips and bits would stick
to the motor. And I've never seen that happen. ?????

John Hasler
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Re: Mounting an INVERTER

Post by John Hasler » Sun Apr 28, 2019 7:20 pm

The small leakage field from the motor won't bother your VFD. It would not be a good idea to bolt the VFD heatsink directly to the motor frame but as you aren't doing so there's no problem.

shorttrackhack
Posts: 42
Joined: Sun May 15, 2011 4:38 pm
Location: SoCal

Re: Mounting an INVERTER

Post by shorttrackhack » Mon Apr 29, 2019 8:26 am

Do what you will, don't take my advice. The motors around my shop that run on sine wave or generated power don't have much of a magnetic field around them, but the ones that run on vfd's will noticeably stick a screwdriver to the motor case. As far as leaving it out in the open in what the CEC calls an area that is not 'safe for open wiring', well maybe you should check with your local Hydro inspector, eh?

shorttrackhack
Posts: 42
Joined: Sun May 15, 2011 4:38 pm
Location: SoCal

Re: Mounting an INVERTER

Post by shorttrackhack » Mon Apr 29, 2019 8:30 am

Just as a side note: In the 10 years that I spent manufacturing machines that ran exclusively on VFDs and three phase motors, I learned the most from the people who refused to read the manual and follow the instructions.

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