VFD problems ?

Hello All,
I have just aquired a new to me Enco 13" lathe. The lathe itself runs very well. But my VFD is giving me fits. About every third or fourth
time I turn the lathe on, I get a OC-C fault on my 3hp TECO 100FM VFD. The lathe has a 3hp 3phase motor. The OC-C fault is supposed to indicate "Overcurrent during constant speed". The causes indicated in the manual are 1. Load changes excessively, or 2. Input voltage fluctuates excessively. The actions are 1. Check load condition 2. install a reactor between power supply and inverter.
The fault will occur on start up with just the 3 jaw chuck as a load. It has never occured, once the lathe has reached running speed. I have increased and decreased the start up time, with no effect on the problem. The load should be pretty constant. I am not sure what a "reactor" is.
Do any of you electronics wizards have an idea of what the problem might be?
TIA
Jake in Escondido
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One thing to check might be the wiring between the VFD and the three phase motor. Is is pretty long, and all bundled together as in, say, some SJ cord?
I have the same nuisance trip problem (maybe one time out of five or ten starts) with the VFD I put on my drill press. I had used some small wiring between the motor and the unit and it's a bit longer than it has to be, so I can pull the drill press away from the wall - and the VFD is mounted to the wall, above the drill to keep swarf out of it.
The only thing I can think is that the 'general protection fault' is because the unit thinks a ground fault is happening in the motor, because of the excess capacitance in the wiring. I think maybe George Glines had a similar issue in a machine of his at one time.
I've been meaning to get some larger SO cord and replace the wiring, with a shorter run. Just need a roundtuit though.
Jim
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Jake,
I'm not experienced with VFD's so I'll take a crack at your problem. (Don't you love it when a neophyte is the first to respond) Anyway, I question why you selected that particular VFD for your lathe. Did the manufacturer recommend a 3hp VFD for your 3hp lathe? Are you sure you shouldn't have a VFD of higher power than the lathe motor? The symptoms and actions you gave seem consistent with a marginally powered VFD - But, again, I have no experience with VFD's. Come in, Don Nichols!
Bob Swinney

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On Mon, 12 Jul 2004 09:18:05 -0500, "Robert Swinney"

Big question is...does this occur high gear or low gear, or in all gears? As Bob said..it sounds like a marginal current starting problem.
Im not familiar with your particular VFD, but check programming and see if there is a min/max current setting and a min/max Voltage setting. Its possible that its going into a brown out condition and is shutting off as its seeing not only too much current, but too little voltage as well. If changing accel time doesnt do anything..check the above.
Gunner, who always puts 2 spare HP (or more) on the inverter when specing one, particularly on gear heads.

That rifle hanging on the wall of the working-class flat or labourer's cottage is the symbol of democracy. It is our job to see that it stays there.         - George Orwell
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Robert Swinney wrote:

The TECO's are supposed to be full rated even with single phase input. I use Allen Bradley 1305's and always derate, since I usually buy used stuff. I've never had an overcurrent fault.

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    I tend to use slightly over-powered VFDs as well -- just because my shop may be hotter than the spec allows for. :-)
    However -- if you are switching between the *output* of the VFD and the lathe, you are very likely to get this sort of thing, because the normal behavior of the VFD is to soft-start the motor -- start with low frequency and voltage and ramp them up to full speed. This takes a lot less current than switching the motor on after the VFD is already up to speed.
    It *also* risks damaging the VFD's output transistors with the high-voltage switching spikes when you turn the motor *off*.
    But if you are letting the VFD start and stop the motor (which is as it should be) and are still getting these, I would suggest that you dig into the manual for the VFD and find out how to increase the start time (the time it takes to ramp up to full speed), because it may be that the inertial load of your lathe and chuck is enough to draw too much current -- without a slower ramp-up time on the speed.
    Note -- you *can* use the switch on the lathe to command the VFD to start and stop the motor, by rewiring things. Wire the motor directly to the VFD's output (so you are *never* tempted to switch the output of the VFD), and run wires from a SPDT set of contacts in the (now free) switch on the lathe to the contacts on the VFD to allow you to stop and start it from the lathe's switch. (If you have a Mitusbishi VFD, I could look up the names of the terminals and the switch configuration for this wiring -- but I don't have data on your VFD.)
    It can be wired for either SPDT contacts to run/stop/reverse the VFD, or individual push buttons (N.O. contacts) to start "forward", start "reverse", and N.C. contacts for the "stop" button.
    But if you *really* want to plug the lathe in and use the switches on it without rewiring, you would be better off with a rotary converter, not a VFD.
    I hope that this helps.
    Good Luck,         DoN.
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Jake in Escondido wrote:

Do you use the VFD to start the lathe - ie. lathe power switch always on, and use VFD start/stop function? If not, this is your problem.
Does the selected speed of lathe change how often you get the error? It should, as the starting torque changes based on gear ratio.. Try it - max speed, and lowest speed of lathe.. The inertia of the chuck is your enemy.. Lowest speed should be easiest on the VFD..
Kristian Ukkonen.
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Sounds like you need bigger wire from the fuse box to your VFD.
I have 3 Teco VFDs and they work well and have never given me a problem. I suggest you check the parameters in you VFD. Particulary max motor current. There are also some parameters pertaining to overdriving the motor at startup. I think it allows significant overdrive during start.
I assume you bought this VFD new. If so, call the seller and ask for technical assistance. I bought my VFDs from dealers electric and harold has been helpful.
If machine inertia is your problem, changing the start time would improve it. Since it didn't change, I suspect your problem is inadequate power supply.
chuck
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snipped-for-privacy@fontaine-etal.com says...

Are you running the VFD on single phase input? Have you measured the line voltage at the inverter's terminals?
Some VFDs can be set to display the voltage of the internal DC bus. If this unit can display bus voltage it may indicate, or help rule out, a problem with the supply voltage. Running the VFD on single phase or low line voltage could cause the "Input voltage fluctuates excessively." condition.
You might also look for "current boost" or similarly named parameter that will allow for short increases in motor current without tripping the drive.
Ned Simmons
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Teco has pretty tech support for these systems, have you tried talking to them- 800-451-8798.
I have two 2HP Tecos on my 2HP mill and 2HP lathe and they've worked fine, including starting the lathe with a heavy 8" tru-adjust chuck on it. They're both running on single phase input with no problems.
As you have probably seen however, there are a zillion pararmeters that can be set on these controllers. If you bought the unit used I would put them all back to the default values as a starting point.
Good luck-
Paul T.
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Jake in Escondido wrote:

Did you actually observe the motor starting slower when you increased the start time? What is your start time set to? What is the overcurrent trip point set to? What is the rated motor current?
Do you have the lathe motor connected directly to the VFD output, with no motor starter, contactor, reversing relays or anything between them? If you left the regular motor controls on the lathe, that is definitely your problem. The VFD supplies voltage proportional to current, so the contactor wouldn't pull in until the VFD was already near 60 Hz. Having relays between the VFD and the motor is a good way to blow up the VFD.
Jon
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Thanks for the terrific responses. It looks like I am going to be busy this Saturday. Now to answer some of the questions.
The Teco unit is new and I picked it up from Dealer's Electric.I have another Teco unit powering my Mill (no problems). I have run the VFD into the lathe, contro box, not directly to the motor. I was hoping to make use of the existing switches and lamps. I have conneted everything with about 10 total feet with #10 solid copper wire from the junction box.
The fault happens both at high and low speed. I have been starting the lathe from the switch below the saddle once the pannel gauge has moved to 60 hz. I do notice a good bit of chatter from the relays as it approaches 30 hz. Until I get things running right I haven't set the VFD above 60 hz. The chuck is a 8" Bison 3-jaw and it isn't lite.
I have run the start time from 4-12 seconds with no effect.
I couldn't find anything in the manual relating to "overcurrent" could "Overtorque Control" be what I am looking for?
Thanks again for all the help.
Jake in Escondido
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    *That* is the problem. You *can* continue to use the switches -- with a bit of re-wiring, to use the switches to command the VFD directly, and the motor wired directly into the VFD.

    Unfortunately, those relays preclude the simple test. Plug the VFD in, set to stop. Turn on the motor switch, and then command the VFD to start. This won't work because of those relays chattering during the ramp-up -- and may actually do more damage.
    Yank the wires from the switches to the motor, connect them *directly* to the VFD, and see what happens just commanding the VFD to start and stop the motor.
    Once you are assured that this works, yank out the rest of the wiring, and run the wires from the carriage switch to the VFD's command terminals. (I think that you'll find the actual switch (or perhaps a pair of switches) in the left-hand pedestal, and run by a keyed rod passing through the carriage and the fwd/stop/rev lever.) You can then also pass the signal through the master switch on the front panel of the lathe, or (as I would be tempted to do) use that master switch and the relays to switch the power on the *input* side of the VFD, so you are assured that the VFD is off the power grid when you are not using the lathe. (This reduces the chance of a lightning strike accidentally damaging the VFD in just such a way as to leave it running the spindle full speed forward or reverse while you are elsewhere.

    So it is not ramp-up time that is the problem -- and since you don't have the motor load present when the VFD is starting, it could not be the problem. :-) That start time setting only affects how slowly the VFD ramps up its voltage and current form when *it* is commanded to start. You're bypassing that entirely.

    Your "overcurrent" is when you are switching a halted motor onto the VFD when it is already producing a standard 60 Hz. So when you stop "beating your wife", you should not need to worry about the settings. It would probably be called a "current limit" or something similar. Each vendor has his own terminology -- I think to make it more difficult for a customer to move to another brand once they know one brand. :-)
    Good Luck,         DoN.
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On Mon, 12 Jul 2004 21:42:35 -0700, Jake in Escondido

Jack, if you are feeding the lathe with the output from the VFD and using the lathe switches to control the motor.... rather than using the VFD remote control terminals and directly controlling the motor..thats your problem as so many people have pointed out. This btw is considered a Bad Thing with many VFDs, and in truth may well kill your VFD. That relay chatter is the first sign that things are Not Right. And each time it chatters, you are sending a transient spike of some size, straight into the VFD.
Its simple enough to wire your lathes control switches to activate the remote input terminals of the VFD.
Im in So. Cal all week long, so if you want to discuss how to do it, simply give me a call at 805-732-5308. Btw..I do machine tool repair for a living, so I do have some small ideer of how its supposed to be done..having done a shit load of them <G>
Gunner
Gunner
That rifle hanging on the wall of the working-class flat or labourer's cottage is the symbol of democracy. It is our job to see that it stays there.         - George Orwell
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Jake in Escondido wrote:

Absolutely WRONG! You are lucky the VFD has not exploded in flames! Read the manual! They all warn, in "glowing language" about having any relays, switches, protectors, etc. between the motor and the VFD.
You will have to disconnect the motor from all that stuff and wire it directly to the VFD.
Jon
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Well rats, there go all of those nifty bells, whistles and safety features that made the lathe so attractive when I bought it.
Anyone interested in trading a almost new Teco 3 hp VFD for a good working rotary phase controller? 8^)
I guess I will be rewiring the lathe this weekend.
It is interesting that when I called Teco tech support today and told them my tale of woe. Then never even cautioned me about the relays other that to say I ought to find out why they were chattering. But what they told me to do didn't work either. 8^(
Thanks again to all that responded.
Jake in Escondido
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etal.com says...

I wouldn't give up so easily. If you think of the VFD as a reversing motor starter, you may be able to replace the function of the existing starter (likely a couple of those relays comprise a reversing motor starter) with the VFD, and leave the rest of the controls as-is.
With a bit of head scratching I did this on my lathe, which has a moderately complicated control, without losing any functionality. Since you already have the VFD it would be a shame to give up too easily on all it's benefits.
Ned Simmons
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wrote:

Yup. Should be quite easy to do. Start out by drawing a diagram of your control switches and what they do and how they do it and match it up to the TECO diagram.
Use your Power On button to close the contact that feeds power To the VFD (think of it as turning on the lathe AND the VFD.
Although rather than using the existing forward/reverse relay pairs..Id go straight to the run switches. and bypass the relays.
Your run forwards, run backwards lever on your compound is USUALLY a form C switch. One way contact A and common are engaged, B is open. Other way B and common are engaged and A is open. Most VFDs work exactly that way also. Ill bet you a buck it will take longer to figure out which switch does what, than to actually hook it up by 2x.
Gunner
"The entire population of Great Britain has been declared insane by their government. It is believed that should any one of them come in possession of a firearm, he will immediately start to foam at the mouth and begin kiling children at the nearest school. The proof of their insanity is that they actually believe this." -- someone in misc.survivalism
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"Ill bet you a buck it will take longer to figure out which switch does what, than to actually hook it up by 2x."
Gunner, that is a pretty safe bet 8^)
I guess I will have to get out that paper and pencil. God, I hate screwing around with electricity. I would prefer to deal with about any other form of metal other than copper wire.
Thanks
Jake in Escondido
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On Wed, 14 Jul 2004 20:10:25 -0700, Jake in Escondido

Jake....if you get really really stuck..and cant go any farther..Ill take a run down there some evening during the week and give you a hand. Might cost you a Jack in the Box burger and $20 or so for gas though..shrug. I work a lot in Orange Country and its about what...90 miles each way from Ontario?
Gunner
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