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Advice for VFD for Bridgeport M head

techymechy

Aluminum
Joined
Oct 24, 2018
I'm getting a Bridgeport M head to install on my Hardinge TM milling machine. The M head has a 3 phase motor. I would like to power it with 120V to the VFD. I have a Servo No 50 variable speed X axis power feed that is sensitive to VFD noise. I installed a VFD on the Hardinge 3/4 HP motor and it caused my Servo feed to not operate correctly (it is a Triac/Diac motor speed control that is sensitive to line noise). I fixed this by installing a filter between the VFD and the 240V line.

I added a power box on the mill by taking power off of one leg of the 240V-4 wire lead I have coming from the wall to the main mill motor. I am powering the X axis power feed from this box and will eventually power a DRO from it as well. I would also like to use this to power the M head/VFD.

Can someone recommend a VFD for this application? I need a VFD that produces little conducted noise and that can be set up for a potentiometer speed control, FWD/REV switch, ON/OFF, etc.

I was looking at these VFD's:

ESV371N01SXC | AC Tech |

Or:

FRN0003C2S-6U | Fuji Electric |

This is for a home hobby shop so price is a consideration.

Do you have a recommendation for a VFD that would work well?

Dave
 
vfd is noisy on the output end, if you needed filter on the 240 side you have all sorts of ground/shield/neutral tangos going on. Leeson drives are much less interference throwing than lenze drives from what I see on different machines. Hatachis dont give interference- they absorb it just looking at them.
 
Thanks so much for the replies.

I used an old AB VFD (Allen Bradley 160S-AA04NSF1 Series C) for the 3/4 HP motor on the mill. I was getting a lot of conducted noise from the VFD which fed back into my 240V system (and hence the 120V leg which I am using to power the Servo 50 X axis power feed). I read somewhere that this drive did conduct a lot of noise. I had to add a Lambda MXB-1210-33 noise filter on the input to the AB VFD and that cleaned things up on the 120V used to power the Servo 50. I was careful with shielded cable for the controls, solder connections for wire splices, etc. and mostly followed the AB manual instructions.

The conducted noise was causing issues with my Servo 50 drive system. This system used a nifty little circuit that was popular in the 1960's for motor speed control:

https://www.electronics-tutorials.ws/power/diac.html

This circuit design is especially sensitive to EMI noise, hence the need for the filter from the VFD.

The ACTech is less expensive than the Fuji (by about $40). I want to insure that the VFD's can handle the full load amps of the motor and hopefully are reasonably quiet. I am thinking of mounting the VFD on the head and want to minimize the stuff on the head (trying to avoid the filter on the head). Once I get the head, it will be more apparent on how to mount these things. I might have to mount the VFD on the chassis somewhere, but I'm not that crazy about this idea (right now).

Thanks for the replies.

Dave
 
have you tried running a separate 110 line to the machine? You can move vfd to wall- far away from sensitive parts. distance is a really good shield. Two feet is miles compared to 2 inches.
 
I did try moving the plug away from the machine and that did work.

My mill is sitting close to the center of a double car garage door and I have a 20 ft 12 gage/4 conductor cord going to my 240V outlet. I would have to run a cord a bit farther to get 120V for the power x axis. A filter seemed like a good solution.

I have a nice 4 outlet box on the mill with a 10A fuse. I can increase the fuse size. I was thinking this would be a convenient plug for the M head, power x axis and (eventually) a DRO. But, you are right, I could power the M head from a separate 120V plug on the wall.

Great advice. Thanks.
 
I do not recommend mounting the VFD on the head, unless it is a sealed unit. I prefer to put it in an enclosure or some people put them inside the base if you have a side access. Go with 3 wire control on the head, momentary buttons for start/stop, and a sustained for reverse. I often build small control units for mills, usually also include momentary buttons for tapping, speed, tach. and ring LED light. Some builds I automate the tapping with an auto-reverse and auto-start based on the spindle position.

I would stick with 240VAC 4 wire going to the mill and you can add two dual gang sockets for drives/DRO. Get yourself a decent line filter, and run that just before the VFD. I typically use shielded motor cables if they are over a couple of feet. Many people go with the Teco L-510 which are inexpensive, and work fine for mills. Alternative inexpensive drives would the Fuji Mini, Automation Direct GS21, Hitachi WJ200, etc. These days it is more about what you can get, many of the distributors are out of the smaller VFD's.

Older mill motors you want to be conservative on the carrier frequency, motor overload, operating range (hz). etc. Replacements can be costly. I assume you have a pulley drive, if it is a Reeves, I recommend operating the VFD at 60 Hz and controlling the speed with the mechanical drive.
 
Hi mksj,

Thanks for the feedback. I did add two dual gang sockets in a box on my mill and did use a good 5 pole line filter for the input line on the AB VFD that I'm using to drive the main 3/4 HP motor.

I currently have my AB VFD set up for a reasonably slow motor ramp and decel and am limiting the speeds between 20Hz to 120Hz. I don't have a Reeves variable speed drive, but have sheaves that I need to change. I use one sheave for the Hardinge vertical head and the slower sheave when I'm using the horizontal arbor.

If you mount the VFD on the side of the machine or in the base (or in my case, the side electrical cabinet), do you use a plug and pig tail to connect the head to the VFD/socket? I think that one can power the VFD w/o a load. I wonder if I should use the existing heaters/relay contacts to power both VFD's and have two potentiometers for speed control - one for the horizontal motor and one for the vertical? I have kept the stock switches which were used for a FWD/REV switch and for a High/Low speed on the 3/4 HP motor. I have disabled the High/Low switch now that I have a VFD operating the 3/4 HP motor but I use the original FWD/REV switch to control the on/off and FWD/REV functions. I am pretty sure I can use the High/Low speed switch to control the FWD/REV and on/off functions of the M head.

Things to think about.
 
Have had pretty good luck with AC Tech and the Teco L510 drives..

On the L510, use the online manual, instead of one supplied in the box. A lot more info on setting up, and wiring different types of switches...

I use a military ammo can with its bottom mounted vertically, for an enclosure. Rubber gasket, removable lid...

Mount can to a sheet of plywood, then I mount a small circuit breaker (for line input to VFD) next to VFD box.

Big enough Hoffman boxes are kind of pricy.... VFD Manual, shows minimum box size...

Plywood gets screwed to wall near machine. Need to move machine?, pull screws, drape over machine, roll away.

Drill holes for wiring at bottom, I usually add a couple holes up top, on the side for ventilation. And rivit screening across them, to keep chips/insects out...

Filter the Power feed... Not the VFD.. Plenty of line filters available..

Using old heaters and wiring, is kind of going backwards.. VFD can do all that, and provide better motor protection... You ARE trying to keep VFD EMI down....

I do not use any type of plug/receptacle on VFD output.. Wire it straight to motor... SOOW type cable if you need flexible cable..

120hz might be pushing a motor more than 50 years old or so... 90hz should be fine.. and 30 hz for low speed..

2 second or so, accel/decell is easy on things..

Use shielded Low voltage control wiring. With shield not grounded at switch/potentiometer end (As Per Manual)
 
Motor is directly hardwired to the VFD, everything else is removed as far as contactors/fusing, etc, between the motor and the VFD. I use locking spade terminations at the VFD end and ring terminals at the motor end, rings for ground. I would not use any of the previous switch gear for the VFD low voltage signaling inputs as the contacts will have too high a resistance from previous use, just buy some decent switches and mount them in a box. I have no clue what you are talking about on the horizontal and vertical motors, if these are drives, they cannot be powered off of the VFD, they should have their own speed controls.

Motor should be limited to 30-90 Hz, beyond that you are probably going to shorten its remaining life span.
 
Hi All,

Thanks for the input.

Great idea to have the filter between the power X axis and the 4 terminal box on the milling machine.

I'll also figure out where to mount the VFD on the mill body/electrical box. I have a later model Hardinge TM that has the large electrical panel on the lower right hand side of the machine which has the relay power interconnect, motor heaters, etc. Originally, the system was wired for 208/230V 3 phase power but I rewired it for 240V single phase. I placed my AB VFD inside the box along with the 5 pole filter.

Since my mill came with the contacts to change the speed and direction, I used these for the existing 3/4 HP motor for the VFD FWD/ON/OFF/REV controls. The switches are very high quality units and work flawlessly. I could use the M head FWD/ON/OFF/REV switch to do the same and place a speed pot somewhere else.

I think you are correct on the motor speed. I'll go change the speed range from about 20-90 Hz and measure the spindle speed for the different frequencies. I'll probably end up using the three slowest sheaves.

I have noticed that many of these smaller VFD's are sold out. UGH...this supply issues is really messing up the availability of stuff.
 
As said above, filter the input to the table drive. A VFD, by nature, will generate noise, and not only going out to the motor, it will come backwards, through the rectifier block, out to your mains. Bypass capacitors on those leads, or an AC line reactor, or both, will help, but the biggest problem is really that your table drive is not well defended from line-based noise.

There's many things you can do with the motor and drive, but keep in mind that the M head was never intended for high milling loads. Wood, plastic, and soft metals will be okay, but it's not stiff nor slow enough to be cutting steels.

The belt drive is the greatest power limiter. Your greatest spindle output power will come with belts in a 1:1 configuration, as that's where both the drive and driven sheaves will exhibit the greatest contact. Any other ratio, you'll have one or the other with limited wrap, thus, your power limit appears there. Since the M-head has no backgear, you'll find that cutting large holes will be a challenge.

I run into no issues running my J-head's pancake motor at 180hz. It has a high enough winding reactance so that it REALLY falls off power at that speed, so I'm rarely pushing that limit. It seems fairly strong all the way down to about 15hz, but I can run it in a backgear.
 








 
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