[popenmann]

I recently upgraded a couple of 201's to 203V and 213V. One machine has been running its "V" drive without issues, so far.

Another identical machine intermittently trips the red LED on its "V" drive. The drive is not the least bit hot and it does not reset automatically no matter how long you wait, so I take it to mean that it tripped due to excessive current. The Gecko troubleshooting guide insists this would be due to a short in the motor or a short in the wiring.

Things I have tried so far:

-- swapped the new 203V with a new 213V. Both drives gave the intermittent red LED error.

-- swapped the Vexta motor (pk299-4.5, 8 wire, 6.3 amps, 880 ounce) for a nearly new chinese motor (1232 ounce, 4 wire, 5.6 amps). No improvement, the intermittent red LED errors continued.

-- replaced the cable between the drive and the motor with a new cable. No improvement.

-- ohmed the motor and verified the correct connections. It seems to be correct, and like I said, it had run OK with a 201 for over 10 years.

-- replaced the correct 420K ohm current set resistor with a 180K ohm. No improvement.

-- verified that the power supply capacitor (Camtronics 36V, 20,000uf) holds a charge.

-- added a 1000uf capacitor between the Gecko's power input terminals. That made a huge difference. With the capacitor, I've only had one red LED error in the past week, running the machine all day long.

-- emailed Gecko for advice yesterday. No response as of this time.

-- perhaps this is irrelevant, but I'll throw it out just in case. About a month ago, while still running the 201, it blew several 5 amp fuses in the supply line. Eventually it would blow the fuse as soon as I applied power, and I discovered that the 1000uf capacitor across the Gecko's power terminals was bad. Replaced the capacitor and no blown fuses since.

Questions:
-- why did adding a 1000uf capacitor make such a huge improvement?
-- is my 20,000uf power supply capacitor big enough ? (it powers two 6.3 amp motors)
-- there is a 5 amp fast acting fuse between the power supply and the Gecko. If the Gecko is sensing too much current, why isn't the 5 amp fuse blowing?
-- Is there something I'm overlooking?

Even one red LED error is too many, since it crashes the workpiece, so I need to either fix the problem or else get rid of the "V" drive.

[MarkC101]

Hi I Have a similar LED on one of my Gecko drives have you had any luck finding out what it?

[popenmann]

MarkC101, the Gecko troubleshooting guide suggests that the red LED error is either overheating or else excessive current due to a short in the motor or cable. If it is due to overheating then the error should clear itself when the drive cools down. If it is due to excessive current then it is necessary to power down to clear the error.

I was hoping Mariss would weigh in and tell me what I am overlooking, because I cannot figure out my issue.

Since my last post, I added a 25000uf capacitor in parallel with the power supply's existing 20000uf capacitor. Perhaps it helped a little, but I still had two red LED errors in the past week. Any error is unaceptable because it crashes the work and costs money. :'(

Today I swapped the two drives around on this "problem" machine. I removed the 213V from the X axis and put it on the Z axis, and removed the 201 from the Z and put it on the X. My thinking was that since both drives share the same power supply, if the problem was due to a glitch in the power supply then the error would continue no matter which axis the "V" drive is installed on. If I can run a week without a red LED error on the Z drive, then I'll assume the power supply is innocent and the problem must be something unique to the X axis.

[ger21]

-- there is a 5 amp fast acting fuse between the power supply and the Gecko. If the Gecko is sensing too much current, why isn't the 5 amp fuse blowing?

If you read the Gecko white paper on power supply sizing, it mentions that the drive will never draw more than 2/3 of the rated current (or what you have it set to). So if you have the current set to 6.3 amps, the drive shouldn't really ever draw more than 4 amps.

[popenmann]

If you read the Gecko white paper on power supply sizing, it mentions that the drive will never draw more than 2/3 of the rated current (or what you have it set to). So if you have the current set to 6.3 amps, the drive shouldn't really ever draw more than 4 amps.

Well, I'm not an electrical guru, so I had to re-read the Gecko paper.

A motor control will always draw less than 2/3 of the motor’s rated current when it is parallel (or half-winding) connected and 1/3 of the motor’s rated current when it is series (or full-winding) connected. That is to say, a 6 amp per phase motor will require a 4 amp power supply when wired in parallel and a 2 amp power supply when wired in series.

That's a bit ambigous. Is it trying to say that current will depend on wiring configuration, or is it trying to say that the factory current spec is never ever the real current draw?

The motor in question is a nominal 4.5 amp motor -- but it depends on how it is wired. The factory spec is 3.18 [Bipolar (Series)]
4.5 [Unipolar], 6.3 [Bipolar (Parallel)]. I've supposedly wired it bipolar parallel.

I say "supposedly" because it's been over 12 years since I CNC'd this machine. It's been running decently for 12 years so I assume I must have wired it right. Usually when a motor is wired wrong you'll know right away because it'll sound terrible and won't have much power. But ..... since I'm running out of things to check, I'll try to verify the motor connections in the next day or two.

Meanwhile, today I've had the machine cycling constantly with the "V" on the Z axis and a 201 on the X axis. I did not put the 1000uf capacitor on the V drive this time, but the power supply has the added 25000uf cap for 45000uf total -- that should be plenty! So far both axes are humming along without incident. Only issue is that the X motor with the 201 runs very warm to the touch. Not hot enought to burn you, but it gets your attention. The Z motor never ran that warm when it had the same 201 drive, and of course it runs even cooler with the 203. One of the reasons I wanted to upgrade the X to the 203V was so the X motor would run cooler. But perhaps the heat could be a symptom of some other problem?

Hence I will verify the motor wiring. Other than that remote possibilty, I am stumped.

[popenmann]

Update: I tore apart the motor connections today to verify that they were correct. It was correct as per the Vexta color schematic, plus I ohmed everything and it seemed normal that way, too.

Each of the 4 "loops" in the 8 wire motor ohmed 1.0 ohm. A to B was 0.6 ohm, and C to D was 0.6 ohm. That's slightly different than the factory spec which is:

0.33 [Bipolar (Parallel)]
1.32 [Bipolar (Series)]
0.66 [Unipolar]

Nonetheless the measured resistances were consistant with each other.

While I had things torn apart I swapped the X axis's 201 current limit resistor from 6.3 amps to 5.5 amps, thinking it might help the motor run cooler, bearing in mind that my main complaint with the 201 was that it made the motor run noticeably hotter than a 203/213.

So far the 213V has been running about 48 hours on the Z drive without an error. And the 201 runs OK on the X drive.

What I have ruled out so far:
-- it doesn't seem to be the power supply because both axis share the same power suppy, and the "V" runs fine on the Z axis.
-- it's not the cable to the motor because I replaced it with a new cable
-- the motor wiring is verified to be correct
-- no short detected on the motor coils with an ohmmeter
-- it's not a defective "V" drive because I've tried 2 different "V" drives on the "problem" axis, plus the same "V" drives are running fine on other axes.

Unexplained mysteries:
-- the "V" also gave intermittent red LED errors with a nearly new chinese motor that I borrowed from another machine
-- adding capacitance greatly reduced -- but did not completely eliminate -- the red LED error on the "problem" axis.
-- if the red LED error is due to a short circuit in the motor, why doesn't the supply's 5 amp fast acting fuse blow while running the 201?
-- if there is a serious short circuit, why has the 201 survived all these years?

I'd like to hear what Mr. Gecko has to say, otherwise I am stumped.

Since I don't have a solution, my plan is to continue running a 201 on the "problem" motor.

[eman5oh]

The V series drives are cpld based and the 201's are analog drives, I suspect that since adding a cap to the drive reduced the trips, you may have a power supply problem. See you said you are using a 36 volt cap, what is your supply voltage? I suspect you may have a supply that is marginal and dips below the required voltage for the V drive and it faults. The V drive would be more sensitive to supply fluctuations. I would give them a call and see what they say.

[LeeWay]

I have had odd issues similar to this. I have even sent the drive back for repair and it was said to be okay. They have repaired several drives for me for various reasons. Sometimes it came down to noise apparently. Another time it was the BOB. Two sets of the drive pins on the BOB went bad. It happens. Replaced with identical C10 BOB back then and it went away.

[popenmann]

Another time it was the BOB. Two sets of the drive pins on the BOB went bad. It happens. Replaced with identical C10 BOB back then and it went away.

That's interesting, thanks for the tip. I might try moving the X axis signals to different pins to see if that makes a difference.

BTW I'm using a straight-thru BOB, no isolation or signal conditioning of any kind.

[popenmann]

I suspect that since adding a cap to the drive reduced the trips, you may have a power supply problem.

Except both axes share the same power supply, but only one axis trips the "V" drive. Hmmm .....

you said you are using a 36 volt cap, what is your supply voltage?

I meant to say the power supply is a 36V Camtronics. I believe the Camtronics cap is rated for 50V, and the 25000uf cap that I added is rated for 75V. The Gecko drive supposedly only requires 18 volts.

I suspect you may have a supply that is marginal and dips below the required voltage for the V drive and it faults.

I can't remember the power rating of the Camtronics supply (it's no longer listed on their website) but I'm sure I sized it correctly at the time of purchase. In any event, since the Z axis shares the same power supply, if the problem were the power supply then the "V" should be tripping on the Z axis, right?

But adding the capacitor definitely reduced the errors. Perhaps the capacitor was absorbing a current surge during motor decceleration? I dunno, I'm not the electrical guru, so I'd really like to hear from Mr. Gecko.

I would give them a call and see what they say.

I don't have a phone, but I sent an email to Gecko on December 11th. I have not received a response. They're probably busy with holiday stuff, so I'll wait until after the holidays and then bug them again if I still haven't received a response.