Thread: Hammer N4400 3 Phase conversion - VFD install

I guess this could go in the electronics section – not sure where is best.

It seems like this project has been quietly stewing for a very long time – I collected the machine in June/July 2019 -
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but I’ve finally got a working super-saw.

I have to say, this forum is a most excellent place. So much knowledge freely available, and so many members willing to give of their time and expertise.

BobL’s VFD install threads started me thinking unclean thoughts about three phase machines; members like MrSlow and PaintMan variously pulled their machines apart and clicked their stopwatches for me.

But it was Chris Parks and Tony Dyer (NCArcher), both of Autoblastgates fame that really went out of their way to help me. Chris organised the Powtran VFD and braking resister, and put me in touch with Tony who has extensive knowledge of VFDs.

The original plan was for Tony to come up to Newcastle and help me with the install, but life got in the way as it often does. In retrospect, I’m kind of glad it did because it forced me to read extensively and work the darn thing out myself. It took much longer, but I have a new set of skills.

So: MrSlow took these pictures of his N4400 3P motor:
Screenshot 2020-03-04 11.07.12.jpg Screenshot 2020-03-04 11.08.02.jpg

…which made it look like an easy reconfigure from star to delta so it could be driven by a VFD. BobL bangs on about checking the actual motor on the machine you’re thinking of buying… (jaws music) and when I collected my saw, the connection box looked like this:

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A different beast entirely. Bigger 3kW motor, and not possible to change the connections in the box. Fortunately I found a gnarled old motor winder locally (the big outfits wouldn’t touch it – liability bla bla etc) who looked embarrassed about charging me $100 to open it up and connect it as delta.

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Chris organised a Powtran PI500 004G1 4kW VFD. Freight costs almost as much as the device, so it’s a pricey option compared to some of the cheap Chinese VFDs available, but I wanted decent quality and reliability. If they run all the clearvues in Aus, they’re probably going to be ok running my bandsaw.

Apart from running the 3P machine on 220V single phase, fitting a VFD has a few other useful options: electronic braking (this is standard on Au Hammer N4400’s, so it’s nice to be able to retain it), emergency stop (the VFD will brake the motor as hard as the electronics and the braking resister will allow), and most importantly, speed control. There’s potential to end up with a saw that’ll cut almost anything with the correct blade.

I was a little bit paranoid about electrical interference – VFD’s make a lot of electronic noise. We live about 5km from the CBD, so of course can’t get terrestrial TV, mobile reception is borderline even with a booster, and the National Broadband Network is the National Broadband Notwork (Straya!)… I wasn’t going to take any chances with the saw generating a black hole every time I turned it on.

I decided to use this hefty double-screened VFD cable. At around $6/meter for a couple of meters, it’s not going to break the bank. It’s 14mm outer diameter, so I had to ream the motor box out a bit to take a bigger cable gland.

VFD Cable.jpg Motor connection.jpg

The big volts go in here – you do not want to be poking the fingers in this place!

For the control cables (switch, speed potentiometer etc), I opted for this screened twisted pair cable. 8 cores turned out to be exactly the number I needed, so that was good! The cable goes into the saw through the hole that the original three phase connector sat on. I'll replace the MDF plate with metal when I have the time to go back to it.

VFD wiring plate.jpg

And for good measure, I stuck a ferrite ring on every cable in site! This is not based on any empirical evidence, but at a few dollars a piece from our local Chinese friends, it costs very little to do.

I also thought I might put it all in a metal box, but everything works without causing a disruption in the time-space continuum without it, so I’ll probably not bother.

I cobbled up a little connector board: I wanted to be able to fiddle about and change the controller box, add or subtract features and so on easily, so the board allows me to undo a few screws and separate it all from the saw quickly and easily.

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I butchered a 220V switch and stuck a little LED and resistor in place of the original neon, so it all runs on the VFD’s 24V supply.

LED switch.jpg

Everything in the control box is low voltage, so it’s much less scary than it looks.

VFD controller - wiring up.jpg. VFD controller.jpg
The grey cable is the screened twisted pair cable, and the black is the original from the microswitch in the saw’s door that stops you starting it up if the doors are open.

It all fits nicely into the original switch position. I’ve left a bit of space above the switch so I can add a display for speed/current draw/whatever at a later date.

switch.jpg

Wiring the VFD is very easy - all terminals are nice and accessible.

VFD wiring.jpg

And the final result – not sure if this is where it’ll stay, but I needed to get it up and running so I can get on with a bunch of stuff waiting for a pile of recycled timber that needs to be re-sawed.

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I’m really pleased with the end result – it’s a fantastic saw.

Still to do – add an accessory motor fan triggered by the VFD when I run it at low speeds; and sort out the dust collection.

It never ends does it…!