PM1440GT Is in the shop!

That document has Mark Jacobs all over it. I sure didn't go down the rabbit hole of shielded motor cables, foil wrap all that jazz. In fact never did with 60HP AC vari-drives. Just not necessary. Extremely long runs end up with a capacitor installed near the motor to nullify spikes in the windings. Your motor full load amps should be around 9.6 amps, so even 14 gauge is sufficient. Regular ole 600 volt insulation class wires will work fine. I ran 14/4 SOOW cable from receptacle to VFD box, then 14/3 SOOW from VFD to motor. The PM-1340GT is only 2HP with around 6.7 or so FLA, so was overkill but readily available.

There was a document or at least a few posts where Mark explained the need for the limit switch installed on the footbrake. It basically disables the programmed regenerative stop using the drive and lets the VFD not "help" the stop but lets the foot brake do it's normal mechanical thing.
 
You do not need shielded wire for the power to the VFD, but it is recommended for the motor cable if it is over several feet. Motor cable shield and the ground wire are grounded at both ends for shielded motor cable, control cables only at the VFD end. Do not tie power cables together with control level (signal) cables, they should be a few inches apart but are fine to cross. I typically bring in the power cables on one side of the VFD enclosure and the control wires on the other. Professional installers will route the different voltage wires in groups somewhat isolated from each other within an enclosure, which is what I do, but for simple installs not a big issue. Just keep the wiring neat, and use the proper terminations, terminals should be properly tightened, and recheched with the power off once or twice afterwards as wires may shift.

I have had issues with electrical noise interference with unshielded motor cable, but also needed a ling input electrical filter. It is optional. You are correct, you need to issue a free run command to the VFD when using the manual foot brake, this requires a dual pole foot switch. I use a separate relay in some of my designs.

You should use ferrules on the control wire connections at the VFD end, use shrink tube or electrical tape on the shield grounds to prevent shorting see pictures below.
ERL-1440C control system.jpg
1440GT Yaskawa VFD Control System.jpg
 
B2 there is a document on Precision Matthews website that has the correct threading and feeding chart. The constant between feed and leadscrew is 4.2405. Looks like you want to cut some non-standard threads using the feed lever? Install an ELS and you can program any ratio you want.

My PM-1340GT had a sticker with incorrect feed rates. I noticed newer ones seemed to have correct sticker. Not sure when change occurred.
 
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With all AC drives, without an isolation transformer (best) or input filter the noise they generate is reflected back on the input lines all the way to the main transformer. The more drives installed the worse it gets. I haven't noticed any problems with a couple small drives.
 
mksj said:
You do not need shielded wire for the power to the VFD, but it is recommended for the motor cable if it is over several feet. Motor cable shield and the ground wire are grounded at both ends for shielded motor cable, control cables only at the VFD end.
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Mark,

I have a CNC mill that uses a 2hp 8000rpm GlockCNC BLDC motor for the spindle. Eveything in the electronics cabinet is well shielded, as well as the limit/home switch cables and E-stop cables.

When I run the BLDC motor over about 5000rpm I get an occasional Estop trigger error. No problems ever, below 5000rpm, but above 5000rpm, the ocurrance rate of the error increases proportional to the increase in RPM.

I'm not sure how familiar you are with BLDC motors and their associated controllers, but it seems pretty similar to a VFD and 3 phase motor, except @ about 500 volts. The power cables between the BLDC controller and motor came hard-wired, with no plugs, and are un-sheilded. Do you think this could be the source of the E-Stop errors? I have ferrites on the motor cables, but no shielding.

Do you think it would help if I added some shielding to the motor cables?
 
Hi @LVLAaron

I am not for sure who wrote the document your you posted. I did not read it closely enough to see if if it is correct or not, but could help you if you need for me to read some specific part. However, the drawings look like those of Mark Jacob's. Plus the phrase "This is only for new machines as used contactors will most likely not work because of increased contact resistance from previous contact arching " sounds like one of his phrases So maybe it is one of his versions. I also noted that the document implies that this is not a preferred approach. Note that it also has a disclaimer that it is 'Untested" and the author takes no responsibility for it. So I would not trust it without understanding it and I would test it along the way.

Recall my solid state VFD conversion: Solid State VFD
Part 1 shows and describes how the original control wiring works.

Also, the electronic brake and the mechanical break are different and the mechanical break should go to a special VFD input, plus coding to cause the motor to stop and to free spin. That is, when you hit the mechanical break you do not want the electronic brake to also be being applied. This would be conflict. So if you look at the schematic Figure 3, Part 2 you will see that for my design when the mechanical brake switch opens it does two things. 1) It shuts off the motor via the latch and 1) it starves the VFD control input 5 EXT of current (takes it low). With the coding that I provided for the VFD at the end of Part 2 you will find the code for Input 5 and EXT. This causes the VFD signals to the motor to cause the motor to free wheel (no electronic braking). It also cuts the current to the Forward and Reverse VFD inputs via the transistors shutting off and it causes the latch circuit to unlatch.

Dave L.
 
BLDC motors are very similar to vector type motors, so you need feedback with a BLDC to control the motor speed. Newer VFD's can drive BLDC motors, so I assume there are the same issues with switching noise. Noise from the electrical switching can be a big issue as well as grounding, but it is often it takes some trial and error. There are also different ways to terminate the encoder shield and noise filters, but I have only used the ones that have been preconfigured and used shielded cable. VFD's I have done hundreds and try to follow the manufactures recommendations, so use shielded for most of the cables. W/O shielding/noise filters I have had cases where other wireless equipment has experienced interference problems. There are different approaches, but my general approach is to try to minimize issues with electrical false signaling and also build several levels of redundancy.

Many people have used the contactors to switch the VFD inputs, it does work if they are new, but contactors are designed for higher voltages/currents. Some very early installs I tried to use used contactors and they were not reliable for low level signals for various reasons, I have also seen this with people that insist on using older switch gear that was used for higher voltages. Still, there are probably 100's of installs with using what I call the basic VFD install with new contactors and I am not aware of anybody reporting problems. It is up to each individual to decide what approach they want to take, but should always strive to make a safe control system and do adequate testing.

As I mentioned previously, if you have a mechanical brake, you need to issue a free run command to the VFD as well as break the run command latch so the lathe cannot restart when you release the mechanical brake. So this requires a dual pole foot switch instead of the stock single pole. One side is for the stock wiring which is NC and brakes the control power (latch), the other side is NO and connects P24 VFD input to the programed free run command input. There are a number of different approaches and this also depends on the VFD model. The switches are readily available, make sure when you install that it is positioned correctly and activates as soon as the brake is partially engaged.
 
Spent the day going through this doc (again, missing attribution, apologies, I saved these docs 9 months ago) and the VFD quick start guide. I'm pretty sure I understand how it's all supposed to work now. Going to sleep on it and focus on getting the box mounted to the lathe. I might end up putting it on a hinge so I can still get to the drive end of the lathe stand without removing the box.
 

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@LVLAaron Are you talking about the foot brake switch?

If so whether you need a NO or NC depends upon your control circuit design and how you use it. You will note in my solid state circuit figure 3 (Part 2), that I use a NC type switch. It is shown at the top of the circuits, right in the center, just below the +24V notation. Hence, I simply used the switch that came with the lathe. No new purchase nor installation change. If I recall the EXT, VFD function input C005 can be configured to receive either logic level, "normally open or normally closed". This is done at input "C015, Input [5] active state 01:normally closed [... ". See Part 2 code sheet at the end of the document in yellow high-lite, pfd (page 48 I think). By the way the 7 VFD logic inputs are defined by the C001...C007 while the active logic levels are defined via C011... to C017. ( It appears that my logic input assignments are different from the document you just posted.... most of them are somewhat arbitrary as to function... you just use the pull down selection tab in the VFD programing.)

The by the way, in the factory circuit, Part 1, Figure 2 you will see that the foot brake switch was wired in series originally with the E-stop and cover inter-lock switches etc. Hence, they had to be NC to operate in series and this is both good and important. The factory did this correctly. There is a big safety concern about using normally open (NO) configurations. Suppose the wire connection fails/comes loose or breaks or even the switch fails (open), then you never know it has failed until you have a need for the function and you need to close the switch BUT the signal cannot get there because of closed cannot happen due to this failure. For this reason you want to hook things like the foot brake and the E-stop up with normally closed switches not normally open switches! Safety First!

Using the EXT input also has another advantage (at least I think it is an advantage). It puts the VFD/Motor into free run (free spin) and after you have an event, you must apply a reset command (my VFD input 7) to the VFD to get to continue to operate. I view the application of the foot brake to be an emergency event. You don't need to use it otherwise as you already have electronic braking. After you have this VFD conversion you will find that the e-brake is so effective that you never use the foot brake unless you have a serious problem.

The I took Mark's suggestion and set the e-brake time to 1 second. The secondary e-brake time (my VFD input #6 and is called Channel 2 (CH2) in the VFD vocabulary) is programed to 3 seconds and that is what I use almost all of the time. I have a front panel switches for these choices. I figure 3 seconds e-braking time causes less wear on the machine, motor, and motor belts than the 1 second braking. I only use the 1 second braking when I am using the proximity stop or if I want the motor to stop more quickly when I am feeding manually. I find that stopping in 1 second is usually over kill. Even in free run the spindle stops pretty quickly even with the three jaw chuck and a work part in it. There appears to be lots of friction in the motor, belts, and all of the gears. The mechanical foot brake IS very effective. It seems to stop the spindle even faster than the 1 second ebrake, but I have never tried to measure it. I will also probably eventually wear.

Dave L.
 
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