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Help starting a bandsaw

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nikoror

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Dec 18, 2012
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#1
I joined earlier today and I already have a question :)

I got a Continental 100M bandsaw with a 2hp 3-phase motor. I am new to VFDs, 3-phase and have very little practical experience with AC circuits.
Unfortunately, with so many new things it is hard to diagnose, but this is what I know.

THE PROBLEM: When I try to start the machine from the start button on the front it makes a clicking sound like cycling a relay or trying to start a car with a very weak battery.

The hardware:

I have a Telemecanique Altivar 31 2hp 1-phase in 3-phase out VFD which I wired as shown in the picture. I only had the start-up booklet in the shop (not the CD with the pdf manual), but I got it to the point where it appears to be working. I have ~120 volts on each of the 3 output legs.

On the back of the bandsaw there is a wiring panel (picture attached) which has some kind of "switch" labeled Cutler-Hammer AE16CNSO. I can measure that all 3 wires at the distribution block (coming from the VFD) have 120 volts. When I press the little brown button (circled in red-yellow in the picture) in the middle of the "switch" the bandsaw starts and (by sound) rpm seem to be fine, but it only runs while I keep the brown button depressed (I used a screwdriver with a rubber handle to do it, didn't want to put my hand there) and stops as soon as I release it. This makes me think that the issue is with the "switch" rather than the VFD, but it is possible that I have the VFD setup to supply a wrong amount of current or wrong frequency.

I have the manual for the bandsaw, but it has a very simplified wiring diagram which does not really help me.

Any suggestions or ideas are highly appreciated.

Thanks,
Nik

bandsaw_100m.jpg
vfd_wired.jpg
wiring_panel.jpg
wiring_diag.jpg
 

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Tony Wells

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#2
In short, the motor starter, or contactor, that you push the button on to force the start, will need to be removed from the circuit. It is no longer needed. The VFD controls all motor functions.

You do have a bit of a problem though. VFD are only designed to control a single motor, yet your saw has a coolant pump. As it is currently wired, the coolant pump motor is parallel with the main motor, to run at the same time. Naturally, the inclination would be to leave them in parallel and let the VFD control both, but that is nto the way the VFD is intended to be used. It might work, but if you slow the saw drive motor down, you will also slow the coolant pump down. Probably nto what you want. If possible, you could change the coolant pump motor for a single phase motor of an equivalent size and mount, or simply substitute a small aftermarket pump like a Little Giant.
 

Kennyd

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#3
Nik, like Tony wrote, the VFD must be wired directly to the motor or you risk damaging it (the VFD). All the start/stop functions are now to be controlled from the VFD. I think I would leave the coolant pump as is for now, if there is problem later you can change it to a single phase pump.

There are quite a few threads on VFD's and how to wire them if you want to study a little more.
 

nikoror

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Dec 18, 2012
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#4
Thank you very much, gentlemen. It was really as easy as following the wiring diagram in the VFD manual :whiteflag:
Got rid of the contactor (which for non-electrical people is just a large-current relay) box which in racing is called weight savings.
Saw works great. Cut some steel and alu as a test, cut the 2x2 faster than I could get the camera ready :)
I had a 25k pot and just for fun wired it in and works great. Haven't really messed with VFD settings yet, but I can make it go faster and slower :)
Now I need to change the oil in the gearbox and change the hydraulic fluid and bring the run switch (don't need a reverse for a bandsaw, right? :dunno: ) and the pot to the control panel on the bandsaw. This will be after the holidays!

Thanks again and Happy Holidays!


As simple as wiring the VFD straight into the motor:
wired_motor.jpg
First cut! 2x2x0.25 wall mild steel
first_cut.jpg
Second cut 1x1x1/8 alu
second_cut.jpg
Wired the pot. Works great (yes, I drink a lot of Coke Zero)
pot_wired.jpg
Weight savings (will probably use for another project, start/stop buttons are cool)
weight_savings.jpg
 

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