New 3 Phase Motor/VFD for my RF45 Mill

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SnakeyJ

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Back before Christmas, I came across a decent quality 3 phase motor (Asea ) and decided to upgrade my Chester RF45 Mill, which I've owned and used for the last 5 years (https://www.hobby-machinist.com/threads/new-toy-s-h-rf45-mill.76666/). The original Chinese single phase motor (750W 1400rpm) motor was still working, but I was frustrated by the limited range and power through the gear box.

I took this motor off when I originally stripped the mill, but it was jammed on solidly when I came to remove it and I destroyed it in the process. Not quite sure how it had got stuck so fast, but there was some rust in the keyed input shaft union and I had to jack it off in stages..

The mill is shaft driven by a 3/4" shaft c/w 15/16" key. The motor mounts by a four hole bolt circle at 90 degrees, with 4 5/8" between centres and the motor has a 5 1/8" alignment ring.
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This photo shows the different motor shafts and keys side by side, old motor armature to right

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My new motor is an Asea MT90L24F165-4, which is a 1420RPM 1.5KW, which appears to have had a very light previous life in HVAC.
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This motor has an identical bolt circle and alignment ring, but has a 15/16" shaft and was keyed to 5/16". This required a strip down, turning down and cutting a new keyway to match the input shaft on the mill. The turning was quick and easy on my Colchester lathe, but with no working mill I had to resort to using the lathe carriage as a manual shaper to cut the new keyway.

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It took a little patience, but got there in the end:
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All now ready to reassemble and mount - tbc in next post!
 
Forgot to say, to drive the new motor I have purchased a 1-3Phase VFD, dubious quality I'm afraid but cheap and readily available on a well known auction site

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Specification:
Application range: Universal
Power supply phrase: Single phrase
Rated current: 8A
Rated voltage: AC220V(single phrase)
Power supply voltage: Low voltage
Suitable motor power: 1.5 kW
Suitable motor type: for 3-phase Motor
Filter: No
DC power supply: Current type
Control method: V/F open loop
Output voltage adjustable method: PWM control

I'm not expert on this, but the output is 240v 3 phase and looks sufficient rated to drive the Asea motor in delta mode, which requires up to 6.4A per phase. Obviously I will need to remove/rewire the existing wiring for the mill to suit

This is my first foray with VFD, so something of a learning experience, but if this inverter fails to delivery I will go back to the drawing board and, hopefully will have gained some useful experience and life lessons!
 
Took a little fine fettling this morning, but motor and mill now united and just thinking around the electrics.

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Not an exact colour match, but does look rather better than the original Chinese motor.

I need to find a 25mm gland to match the motor wiring box as the stuffing glands I have do not have the right thread. However, having opened the box I can see that the motor is currently 'jumpered' to run in 380V star. I will change this to run 240V Delta according to the diagram (moving the three brass jumpers across):

1681130907813.png


I plan to retain the existing supply and NVR switch to supply the VFD, but currently scratching my head at the mounting options. Ideally I would like this all on the mill, but the VFD housing is cheap tat, lacking even cable entry glands/knock outs and posts to secure the input/output wiring. I expect I will need to re-house this and just searching the web for some inspiration.
 
I have the same VFD on a Bridgeport clone.
I enclosed it in a box on the lower back of the mill. Then ran wiring to a box that I mounted on top of my DRO box for the controls. As such, the lack of strain relief on the VFD became a non-issue.
The control panel for the VFD is removable/relocate-able, and I did move it into the control box with an extension cable that I bought with it. But, I don't trust the quality of those "bubble buttons" or the included potentiometer. I just the panel exposed in case I ever need to do any programming of the VFD.
 
Thanks @Shotgun, I will have to work on an enclosure for the VFD, but just mulling through some ideas at the moment.

I now have the mill up and running, but only for a bench test as I still need to find a 25mm gland for the motor and come up with a mounting solution.

I had a couple of minor scares - the first was an Error8 displayed on first start of the VFD. This was immediate and prevented any further operation. According to the supplied instructions, which for once were written in pretty decent english, this was an overheat warning. The unit itself is supplied with one (2 wire) 30mm fan but has mounts and a circuit board riser for a second. I had fitted a second one, but the error went away when I removed this.

The mill spun up on the second attempt, but sounded rather noisy/clunky. Although the VFD was set to forward my spindle was spinning in reverse. The noise went away when I changed the VFD to run in reverse, so possible that these gear heads were never designed to run backwards or the gear box is just worn in forward? Thinking that a slow reverse might be useful for tap extraction.

A short video clip of the mill running forward and then reverse (opposite to the indication on the VFD panel) - I will swap the motor supply over to put this right. Not sure how fast this is actually spinning, but I will put a hall effect RPM sensor on the spindle so that I can readily see this.

 
You have it set to F, or frequency supplied. Once you've programmed it for the frequency it was designed for, and the RPM at that frequency, it will tell you the RPM when you switch to that view. Won't be very accurate, but close enough. Put the hall effect on they spindle if you can. Much more useful there.
 
Question for you guys on switching the RF45 to 3 phase vfd. I have seen people mention troubles with switching geared head mills to 3 phase on other threads some going so far as to suggest converting them to a pulley drive system first. This left me the impression that vfd 3 phase and a geared head was a no go. Obviously you have done this. Do you know why these other threads are hesitant? These might have been cnc related threads. Makes me think they were just interested in a purely vfd driven speed control. Are you able to get variable speeds through the vfd with your conversion and how does the geared head work into that?
 
There is no difference between a single phase motor and a 3 phase motor running at the same RPM with regard to a gear head. The problem is when they want to drive the gear head at higher RPM. Typically I recommend a gear head is not exceeding 75 Hz or about 125% of the base speed of the motor. Higher speeds are typically achieved through a belt drive, and also requires the spindle bearings to to be changed. Due to the loss in Hp and the loss of mechanical advantage of torque below the base speed, the motor is usually up-sized, so something like 3 Hp. It is run to higher Hz like 20-180Hz which requires an inverter/vector type of motor.
 
It seems to work fine and nice to have soft start and more control on my mill. I normally run between 35 and 70hz, which gives a nice upgrade in rpm for smaller end mills.

The gear head is fine in fwd, but a little noisy in reverse, probably due to wear.

I've seen a few belt and pulley mods - probably run a lot quieter and smoother, but lack power at lower speeds.
 
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