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4th March 2020, 11:52 AM #1
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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 -
D077ED19-B7B9-42D3-A4B3-98BC01F73A95.jpeg
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:
E7568EBE-ED1E-4ECB-AE38-55CB457DA966.jpg 995FA37F-CCED-412E-9E8E-11EE6B39DBA8.jpg
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.
IMG_9507.jpg
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.
electrics.jpg
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.
VFD install rear saw.jpg VFD installed rear view.jpg VFD Install three qtr.jpg VFD full saw.jpg
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…!
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4th March 2020 11:52 AM # ADSGoogle Adsense Advertisement
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4th March 2020, 12:35 PM #2
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Looks great!
One thing I would suggest is remote mounting the VFD screen so you can see the output from the operating position.
I could have done this with my VFD but because my VFD is quite small I mounted it on an angled bracket as shown below.
I've also remote mounted an additional on/off switch and speed pot in a moveable plastic box (above the earmuff safety sign)
The box has a magnet glued to the back so I can move it closer to where I can more easily reach it.
My motor has a built in double speed fan so I can run it at low speed without a fear of it over heating.
I did think about installing an electric brake but I was concerned about what a high speed braking event might do to a narrow profile blade.
The BS does have a foot brake so I can stomp on it hard when I'm using wide blades (~2 second stop) but brake a little more gently with narrow blades (>5 seconds stop).
CompleteBSC.jpg
What range have you set the max linear speed of the blade for?
FWIW we're 2.5 km from CBD and I have 10 VFDs in my shed, none have shielded power or control cables. The AM reception in the shed was not that good to begin with and VFDs definitely make it worse.
Wifi in shed is poor with or without VFDs running. AM radio problem solved by going to a digital radio.
No probs with broad band or other issues up in the house, mobile phone reception is ordinary/average but VFDs being on make no difference.
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4th March 2020, 01:50 PM #3
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Bernard, all good things come to those who wait, or so we are told. The Operating panel can be connected to the VFD via a cat 5 or 6 cable, pull the panel off the VFD, remove the bridging connector plug the cable in. The fan on the VFD can also be temp controlled via a temp switch of some sort, Tony would be able to supply the detail on that. It switches the VFD fan on at 40C to avoid having to listen to the whine all the time. I have done it to mine and the only problem it presents is that I keep forgetting to turn off the power before leaving the shed. Alan Flett also did it to his as well and we both like the silence.
This looks like the switch myself & Fletty used, he got them from Ebay
KSD 9700 Temperature Switch Thermostat Thermal Protectors. 40 to 150 degrees | eBayCHRIS
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4th March 2020, 02:12 PM #4
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Good suggestions there Chris & Bob - I could put a magnet on the back of the VFD keyboard and have it somewhere visible as Bob suggests. It would save me figuring out a separate display and putting it above the on/off switch (which wouldn't be visible from all angles anyway.
So far, the VFD fan only switches on when I run the saw - it powers down pretty soon after stopping the saw. It hasn't bothered me yet as the dust collector is a howling banshee in the shed so I have to wear earmuffs anyway. May change once it goes outside I guess.
Bob, at the moment I'm running a max of 50Hz, which I believe translates to the standard 1200m/s on the N4400. Haven't been brave enough to up the frequency... yet!
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4th March 2020, 09:35 PM #5
Nice work Bernard. Great to see it all up and running. And thanks for the link
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5th March 2020, 09:47 AM #6
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I think you mean 1200 m/min which makes it close to 4000 ft/min which is pretty good as most small Bandsaws (I call a 36" wide cut with a 60HP motor bandsaw big
) are around 3200 ft/min
FWIW the optimum speed for cutting wood with a Bandsaw is ~5500 ft/min
BUT
Unless an operator is used to this it's pretty scary, and things run hotter so depending how long the cut is some form of cooling may be required. On bandsaw mills water cooling is used but this is impractical in small workshops. However if the cut is not a long one as is the case in most DIY workshop, it is possible to run the blade without significant overheating. There are some benefits in shortening the time of cuts as a running saw always represents as risk and the longer a cut takes the greater the operator fatigue.
FWIW my BS runs @ 3200 ft.min at 50Hz, so I set the highest frequency to 4800 ft/min but I usual don't run it faster than than 4500 ft/min.
I also cut a lot of curves in Al plate with my BS. Optimum cutting speed for Al is around 1000 ft/min which translates to ~16 Hz but I usually run it @ ~20Hz (1300 rpm) and rub hard wax along the line of the cut as a lube. Cutting Al can be done at any speed but the lower speed plus wax lube produces a cleaner cut. The moto is quite happy to run at 20Hz for long periods because at that frequency the motor has a double speed fan that is effectively running at 40Hz.
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6th March 2020, 01:50 PM #7
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So if it's a straight fpm/hz calc, 60Hz should give me around 4800 fpm, and 12.5 = 1000fpm.
I may play with it a bit. Need to find a decent server fan before I start dropping speeds though.
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