VFD conversion via solid state electronic components. PM1440GT, VFD, 3-phase

B2

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VFD conversion using solid state electronic components.

I finally finished documenting my PM1440GT lathe VFD conversion and want share it. It took me longer to write this up than it did to actually build the new electronics! (Are these sorts of things every really finished?)

I apologize upfront for its being so long. I just wanted to make it complete before I posted it so that most of it was at the same posting... but it seems there is always something else to add. Also, this is my memory document... so I can fix or improve the installation after I have long forgotten what I did!

I replaced all of the original mechanical relay controls with discrete solid state components. I have not seen any other post where people got rid of the mechanical relays in this lathe conversion, but surely they have so on others. In doing so I was also able to also eliminate the large power transformer. Hence, the space requirements significantly decreased and I was able to get everything into the original lathe enclosure with room to spare. It even includes a homemade, inexpensive, 50 Ohm 400 watt (or a 37.5 Ohm by 300 watt) braking resistor. So there are no external cabinets or enclosures. Only a power switch at the wall. The value of this braking resistor can easily be changed to other values if so desired. Additional features such as proximity sensor, drive frequency display and RPMx10 display, alternative e-breaking rate, auto/manual coolant, +-Jog, etc. are included along with more safety factors. It has been completed and being used for several months without any observed problems or failures. I have made enough machining mistakes to believe it is quite safe.

There are two separate Parts to the document. Skip Part 1 if you do not need to know how the original factory built 3-phase power system was constructed and operated. Part 2 is the detailed description of the new VFD system. Part 1 contains text, figures, tables and photos, but there were too many photos to include them in Part 2. There is also a list of parts and suppliers near the end. Part 2 has a table of contents with links to the text, hence you can quickly jump to the text points and the figures at the end.

The technical description is long so it may be faster to get an idea of things by just looking at the figures, which are included in the document, and the pictures, which are separate due to their size. If you think you are serious about doing a similar conversion, then have a read! I have tried to put enough details in it to allow even someone who has not worked with transistors for a while to understand what is going on. I have also tried to provide a limited description of how this VFD works and is set up. You may not need these.

I wish to thank the HM folks for their many posts. Since I had hardly worked with inverters, or designed for one before, these posts were very helpful. Mark's (@mksj) posts, especially in suggesting the VFD model and its program settings are much appreciated. Private discussions with @ptrotter were very helpful and also appreciated.

Let me know, what you think, concerns, what I did wrong, etc. I welcome ANY question.

Dave

PS. I am not for sure if I can post all of this in one try so it may take a few attempts. I also have other photos if any body needs to see them.
PSS. I also apologize for the obnoxious footer on the document. This is driven by the HM Rule #15. The folks at HM say that they will be making this rule more friendly in the future.
 

Attachments

  • PM 1440GT Part 1 FacOriglElecDescript DNL L910_1440.pdf
    1.8 MB · Views: 341
  • 07b IMAG3287 Front Panel Finished_Prox Stop IMAG3287.jpg
    07b IMAG3287 Front Panel Finished_Prox Stop IMAG3287.jpg
    3.3 MB · Views: 521
  • 08a IMAG3313 Rear Final IMAG3313.jpg
    08a IMAG3313 Rear Final IMAG3313.jpg
    4 MB · Views: 479
  • Figure 3 PM1440GT Part 2 VFDDescript links DNL L910_1440.pdf
    241.1 KB · Views: 256
  • PM 1440GT Part 2 VFDDescript links DNL L910_1440b.pdf
    1 MB · Views: 283
  • 08b IMAG3013 Rear IMAG3013.jpg
    08b IMAG3013 Rear IMAG3013.jpg
    3.4 MB · Views: 438
More pictures ...
 

Attachments

  • 07a IMAG3290 Front Panel Finished IMAG3290.jpg
    07a IMAG3290 Front Panel Finished IMAG3290.jpg
    3.3 MB · Views: 342
  • 08c IMAG2618 VFD HeatSink plate IMAG2618.jpg
    08c IMAG2618 VFD HeatSink plate IMAG2618.jpg
    3 MB · Views: 311
  • 09a MAG2616 Braking Resistor IMAG2616.jpg
    09a MAG2616 Braking Resistor IMAG2616.jpg
    3.6 MB · Views: 315
  • 10a IMAG3146 Hall Spindle IMAG3146.jpg
    10a IMAG3146 Hall Spindle IMAG3146.jpg
    2.6 MB · Views: 334
More Pictures 2
 

Attachments

  • 11a IMAG3002 Circuit Bd Final IMAG3002.jpg
    11a IMAG3002 Circuit Bd Final IMAG3002.jpg
    4.4 MB · Views: 304
  • 12a IMAG3269 Conn Bd E and Cavity IMAG3269.jpg
    12a IMAG3269 Conn Bd E and Cavity IMAG3269.jpg
    3 MB · Views: 265
  • 13a IMAG2622 Rear Empty IMAG2622.jpg
    13a IMAG2622 Rear Empty IMAG2622.jpg
    2.9 MB · Views: 267
More Pictures 3
 

Attachments

  • 14a IMAG2858 Lathe Front Gear Detents IMAG2858.jpg
    14a IMAG2858 Lathe Front Gear Detents IMAG2858.jpg
    3 MB · Views: 274
  • 15a IMAG2992 Front Panel Milled no Prox hole IMAG2992.jpg
    15a IMAG2992 Front Panel Milled no Prox hole IMAG2992.jpg
    4.3 MB · Views: 346
  • PM1440GT VFD Solid State ConvRear panel ppt notations L711_1343.pdf
    373 KB · Views: 195
What an ambitious project! I am in the process of writing up my d.c brush motor conversion on my lathe but you just set a very high bar. Well done!
 
@B2
You sir - deserve our thanks, and admiration. This stuff so generously shared is a resource for folk to learn from, and it it useful beyond the set of PM1440 owners.
 
Thanks Guys, I appreciate your feedback and your "Likes".
Dave
 
Well done! Love the point-to-point wiring on the breadboards! True hacker stuff there!

Reminds me to dust off that RPM display and VFD still in a cardboard box awaiting my attention. I like to age my parts for about a year for some reason. One thing that I considered was to have two braking levels. One would be your normal everyday "stop" brake and a stronger "OMG" brake. I have not completely planned that out yet.
 
Last edited:
Hi @Reddinr

Thanks. Yes, some electronics do need a burn in to assure that they are going to last. So far I have not had a problem so the burn-in is happening real time. I built more than one of these circuit boards before I settled in on this approach. The real issue was how to fasten the board in and the electrical connectors. I tried other connectors and many of them were intermittent. The board carrier and the screw down, push on connectors seem to work well. Now that it is all working well and values are set one could make a neat custom circuit board. I either use tinned wire ends or ferule crimps to go into the elevator style screw connectors. After putting them in to a reasonable torque I wait a day or so and then tighten them again. The wires or ferules or the screws seem to compress and relax a bit. So the second time around they are very secure. You also will see the LEDs on the board. Not neccessary, but nice to know what is happening. One could also design for a much smaller voltage than 24V.

The Hitatchi VFD has two programmable e-braking rates. I put these in and programed one to 3 seconds (called CH2) and one to 1 second. This is switched at the left side on the front panel. The E-stop invokes which ever the switch is set to. However, on the PM1440GT there is a foot break that really stops the spindle fast. Faster than 1 second. When that is hit you want to the e-brake to NOT happen as that would be a conflict between the two rates, electronic vs manual. So the VFD is programed let the spindle free wheel (coast) when the foot brake switch is tripped. I also consider the foot brake to be an "OMG" situation and so it is set up to cause the VFD to go to an interrupted mode, where you have to Reset (USP) it completely before you can run the motor again (safety). There is a Reset (USP) button on the front panel that is recessed actuated... to make it hard to get to.

Dave
 
Holy cow Dave, That's quite a write up! Thanks for sharing, I'll have to check it out more when I'm at the house. To much info for my phone.
 
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