vfd spindle start/stop problem

[endgrainguy]

I'm trying to set up a high frequency spindle, 220 V, 8 amp, 400 HZ, 24,000 RPM using single phase 220 power through this VFD:Hitachi SJ200-015NFU. I'm getting lots of trips, mostly on deceleration. I can get it to not trip only with very sensitive setting of deceleration time, and even then it's not reliable -- it will trip maybe 1/3 of the time. Ideal time to set decelration ranges from 2.5 seconds at 272 HZ, to 4 seconds at 385 HZ. The slower I start from the more reliable the stop without tripping. If I set the deceleration time too long it will trip when it reaches about 40 HZ -- in other words pretty slow. It will then give me error message 02 "overcurrent during deceleration", probable cause ranging from "inverter waas short circuited" to "Load too heavy". If I set it for too short a time, it will trip early in its deceleration, and it will generate code E07, "Over voltage protection", probable cause -- "DC bus voltage exceeds a threshhold due to regenerative energy from motor. " It also trips sometimes on start up, giving me the E02 or E03 (overcurrent on acceleration) error message. Its much more likely to trip on start up if it didn't trip on finish the preceding cycle.
Motor seems to spin fine, and is quiet in operation. I"m not cooling it as well as I"d like, getting 3-4 GPM of water through the spindle, and so only making brief tests of a few seconds.
Any suggestions for what's happening here and how to fix? The manual is more than a little over my head, though I can follow how to implement parameter changes. I just can't figure out which are most likely to help. The tech help at Hitachi was pretty much worthless, just blaming my motor with no suggestions on fixing the problem.

[HuFlungDung]

Does the manual make any references to a braking resistor? Might be that is what you'll need to rapidly dump the energy from that motor. Hopefully they'd tell you what terminals to hook it to. I've heard that Haas uses something like a stove element for a braking resistor. I have no ideas on what size or how to hook it up.

[Al_The_Man]

It could also be aggravated from the fact that you are using the single phase supply which now is usually 240v as standard, if the VFD is made to operate of 220v, this extra now added to the +DC could decrease the margin limit that is caused by the BEMF/braking.
Does the unit have self tuning?
As Hu said, most have an option to fit a braking resistor.
Al.

[endgrainguy]

Thanks for those suggestions. I seem to have it solved by programming in a slow deceleration to midspeed, and a sharp ramp to stop from there. How fast can most of you guys start your spindle? Mine needs a good 15 seconds up to full speed to avoid tripping, though maybe this will be better when I get better cooling for the spindle (higher water flow, maybe a cooling radiator). This has been a bear of a job for me, and thanks to this forum for helping me out. I"ll probably have issues soon around relay, and finally adding a safety charge pump to my system.

[HuFlungDung]

Perhaps you should have selected the next largest horsepower size in your VFD so that you could pour the amps to that motor to get it going. Alternatively, there may be some room to tweak the parameters in the VFD so that you could permit a larger full amp draw.

I ran into somewhat of a similar problem when I put a VFD on my cold saw, and I wasn't encumbered by not having a 3 phase input either. A VFD that matched the motor horsepower was simply too often on the verge of tripping, which it did. So I bit the bullet and bought the next larger size. Normally the full amp draw on a motor is allowed to be 150 or 200% of nameplate amperage, for a few seconds. But if you input the exact nameplate amperage into the VFD parameters, that will be the limit no matter how hard the motor is sucking on the wires

[TOTALLYRC]

Originally Posted by endgrainguy Thanks for those suggestions. I seem to have it solved by programming in a slow deceleration to midspeed, and a sharp ramp to stop from there. How fast can most of you guys start your spindle? Mine needs a good 15 seconds up to full speed to avoid tripping, though maybe this will be better when I get better cooling for the spindle (higher water flow, maybe a cooling radiator). This has been a bear of a job for me, and thanks to this forum for helping me out. I"ll probably have issues soon around relay, and finally adding a safety charge pump to my system.

I use a similar VFD on my bridgeport mill with the 3hp motor and a 3hp vfd.
I can start the motor in under 1 second and stop it in 1 second, without using external braking resistors. It took quite awhile to get the mach3 settings aligned with the vfd settings. If you put a ramp/delay time into Mach3 and then try to stop the vfd faster that this, it will fault.

Your 24k rpm spindle will probably coast down in about 10 seconds by itself. My 3hp motor and spindle will coast to a stop in about 5. Keep tuning and tweaking.

If you are still having problems, let me know, and I will go write down the pertinate settings from mine and send them to you.

I wanted to get their setup software, which is free from their website, but the cable is like $150 to talk to the drive. The software allows you to set the drive parameters all in one shot, and then download it to the drive.

Mike

[endgrainguy]

I'm running the 24,000 RPM 2.2 KW , 400 HZ, 8 amp 220V spindle from Chinese Ebay vendor, with a Hitachi SJ200-015NFU VFD with single phase 220 input. I solved the deceleration trip problem I was having by programing a relatively slow ramp (6 seconds) down to 1500 HZ, and then quick stop (1.5 seconds) from there. Many cycles now with no decel trips. However, I can't figure out how to get it to not trip sometimes on acceleration. Usually if it it trips , (maybe 1/3 of starts) it will be in the first second or two. The obvious move of giving it a longer acceleration time makes it worse. There seems to be some sort of build up in the motor such that avoiding trips is a balancing act of not too fast, not too slow.
Maybe a helpful identifier of what's going on is that before I figured out the two ramp deceleration solution I simply experimented with different deceleration times, and from any given frequency there seemed to be an ideal time that worked most of the time (easier to get it to stop without trips from slower speeds). In these experiments I observed that its likelihood of tripping on the acceleration ramp was many times greater if it didn't trip on previous deceleration. In other words, if it tripped on decel, and then I hit reset, it never tripped on the following acceleration. So I"m wondering if anyone has some brilliant ideas on how to get it to not trip on acceleration. I'd consider going up to the 3 HP drive if that would likely solve this problem.
This is all a bigger deal for me than it would be for many since I use my machine largely for production woodworking joinery work (with spindle held horizontally) -many 20-45 second little repeat cuts, and I often use the bit itself to index the part, so leaving it running from cut to cut isn't an option. If I go up to the 3 HP drive, do I risk damaging my spindle by allowing more current in? The current drive, like the spindle is rated at 8 amps. The next drive up is rated at 11 amps. Also, if I switch to the bigger drive do I need to increase the VFD cable (currently 18 guage)? In fact, could this cable (about 10 feet long) be part of my problem?
By the way, I did some test cuts and the spindle cuts beautifully, incredibly vibration free, a huuge step up from Bosch 12 amp router, and blissfully quiet!

[HuFlungDung]

How did you initially size the VFD? If the motor is 2.2KW as you stated above, you definitely need a 3hp VFD, and perhaps more if it is derated because of single phase input.

[endgrainguy]

I wrote both Drives Warehouse, and Wolf Automation, and gave them all the motor parameters. They both recommended the drive I got, based on the 8 amps. I specifically asked the guy at Wolf about the 2.2 KW issue, and he assured me it was the amperage that mattered. But maybe they were both wrong? I"m certainly willing to swap to the bigger drive if it will help, especially if Wolf will do an exchange. The Hitachi manual actually recommends 10 guage wire for terminal wires for the 3 HP 2.2 KW drive. Doesn't that seem excessive? It takes in up to 24 amps at 220 . So the one I have allows 17.5 amps. Wow, that's at 220 --compare that to a 3.5 HP router -15 amps at 110 V!

[Greolt]

I run the same VFD and same spindle. The SJ200-015NFU works great. 240v single phase.

You do not need Mach to ramp the speed, the VFD takes care of that. Mach just has to pause and wait while the VFD does it.

I interface Mach with one of Peter Homman's Digispeeds. Works a treat.

Auto tuning on the Hitachi would not work for me. It kept tripping.

From memory I use a linear ramp.

Won't be home for a week so can't give more detail till then. Memory not that sharp.

Greg

[TOTALLYRC]

For safety, and to prevent broken tooling, you can use the drive at speed output into mach3 and then have mach wait until the signal comes in before moving. Might take a little vb knowledge, but it shouldn.t be too tough to implement.


That particular drive doesn't have to be derated when using 1phase input power. I would verify that you are using the correct terminals for 1ph input, as I found that confusing. According to the directions, you can't just use any 2 of the 3 input terminals.

Mike

[HuFlungDung]

An 18 guage wire supply to the VFD seems a tad on the light side. I think even a cheap extension cord is 16 gauge. I'd probably go with 10 or 12 gauge wire just to be assured that the conductors are never going to contribute to any problems.

Going to the larger VFD is never going to hurt. You can always derate a VFD that is too large (to protect the motor), but you cannot do anything if the thing is too small.