What's new
What's new

VFD OVER VOLTAGE AT HIGHER RPMs

jtcooper2008

Plastic
Joined
Jul 28, 2020
Hello All,

I recently bought a Lenze 8200 2.2KW 230V VFD used. I am pairing it with a 400Hz 2.2K 220V 24000 RPM spindle.

I finally got the VFD configured to put out the right frequencies, current, ramping/decel speeds so on. So powered it on and all was well I can control the speed however any time I go above 200ish Hz or 12000 ish rpm the VFD shoots out a overvoltage warning and clicks of the spindle. I found the parameter to read out the DC bus voltage and it seemed high. At 100hz it was around 355V and at 200 it hits 390V tripping the overload.

I did a little digging but almost all the things I read talked about DC voltage overload during deceleration due to the spindle becoming a generator. I currently dont have any external braking resistor hooked up, I will soon, but I dont think that has anything to do with my issue. I tried running the VFD without my spindle and across all frequencies it read 340V.

I am hoping someone with more experience can tell me whats going on. A few notes below.

Thanks,
Cooper

VFD input power: 240VAC (in spec)
VFD drive current max: 9.5A
VFD motor output voltage when the over voltage occurs: 120ishVAC
Motor voltage: 220V
Motor body grounded to VFD
 
Maybe provide us with the motor parameters you entered into the the VFD, model number of the VFD and motor plate picture/characteristics.
C0087 Motor rated speed the maximum permissible is 16,000 so unclear how you plan to get to 24,000 (parameter limit based on 2012 manual).
C0088 Motor rated current would be 9.5A
C0089 Motor rated frequency would be 400 Hz (based on 24,000 RPM)
C0090 Motor rated voltage would be 220V (at 400 Hz)
C0091 Assume the default
C0092 would be set when you run C0148 which identifies the motor type, I would run this after setting C0014 to 4 Vector control. You must run C0148 to identify the motor before running it up to speed.
Still a bit unclear as to how you plan to get to maximum motor speed, reading the AC voltage with a standard voltmeter is going to give you misleading AC volts.
 
You probably want to turn the carrier frequency up to around 6-10kHz if not done already. Having the carrier too low will give you few pulses per cycle and that could cause timing issues.

You might also want to oversize the drive, as high carrier frequencies cause it to dissipate more heat.
 
Can you snap a photo of the spindle nameplate and post?

Generally a spindle is rated at a specific voltage and frequency that defines its power rating (this operating point is when field weakening begins) . . . then their is typically a max speed and associated frequency and current rating.
 
It is possible it is a built-in "feature". There are some limits on VFD performance because very high RPM is associated with 'doubtful" activities like centrifuges for making nuclear fuel. I did not think 200 Hz is high enough, but that may depend on the maker of the unit.

Also possible that there is a "pump-up" effect due to the number of pulses per second (carrier). That is a "feature" of switched circuits.... the motor is an inductor, and if it is not drawing as much current at that speed (pretty likely), you can get a "pump up" from the spikes as the devices turn off. A higher carrier MAY help, or it may just create more heat.

The resistor actually should help with many VFDS, because it is usually triggered by overvoltage and not necessarily by "mode".

You also may be able to find the parameter that sets the overvoltage trip. The 390V is a little low, and kicking it up a notch may help. I'd not go over 420V, and I WOULD combine that with the resistor.
 
Thanks for all the insight.I am going to try and respond to you guys in order.

To mksj:

C0087 16000 RPM
C0088 9.5A
C0089 400hz
C0090 230V
C0091 .85
So all of my testing to this point has been in the default V/Hz control C0014 = 2. I tried C0014 = 4 and setting C0148 to 1 but the second it starts running it give a OC3 fault. Possibly related when C0014 = 4 I can get the motor to spin at all and it just seems stalled. Any ideas?

SomeoneSomewhere:

I am not 100% sure what you mean by carrier frequency. Assuming this is the same the inverter switching frequency is set to 8Khz.

Motion Gure:

I got the spindle used on EBAY for 25 dollars shipped. I am a sucker for a bargain. I only has the 220V, 2.2kW 24000 and 400hz written on it. I suspect its this spindle based on looks. https://www.amazon.com/Bearing-Spindle-Engraving-Milling-Rpm24000/dp/B011971H90

JST:

So my resistor arrived and I got in installed and now I indeed can run at 400hz. Its clear whatever caused over voltage issue is still occurring and that resistor is getting hot. I can see the DC voltage build up drop and repeat. So this "works" but I would like to understand the issue more deeply. I do not see any way to set the DC voltage limit and after a little digging it looks like it hard coded. Please take a look and the manual and tell me if im wrong. https://download.lenze.com/TD/E82EV__8200 vector 0.25-90kW__v3-0__EN.pdf
 
The limit may be hard coded. The only settable thing I found seems to be for the resistor cut-in voltage. C0988.

You can try setting that as high as you can get away with, but the issue is probably not going to go away from that.

I am not quite seeing how this problem is occurring. There may be some factor here that has not been discussed. The drive seems to be (or some models are) usable as a "system drive" with a common DC bus, and that may be related.
 
Thermite:

Fair enough but it was also the height of the covid scare and I just happen to be the only bidder. My understanding about the usually goes bad in these are the bearings and my plan is to replace them with proper angular contact bearings. But the runnou appears to be fine with some horizontal cutting force I applied. But I agree that these spindles are low quality and at some point I will like upgrade for a better used spindle, like $35. Maybe an old used milling head.

JST:

Well thanks for taking the time to look. I'll play around a bit more and see if I can get things running a little smoother without so much heat.

Thanks,
Cooper
 
Thermite:

Fair enough but it was also the height of the covid scare and I just happen to be the only bidder. My understanding about the usually goes bad in these are the bearings and my plan is to replace them with proper angular contact bearings. But the runnou appears to be fine with some horizontal cutting force I applied. But I agree that these spindles are low quality and at some point I will like upgrade for a better used spindle, like $35. Maybe an old used milling head.

JST:

Well thanks for taking the time to look. I'll play around a bit more and see if I can get things running a little smoother without so much heat.

Thanks,
Cooper

Ummh. .well. I'm trying to NOT mess with bearings as require a proper "clean room" and not-only on my two "Precise" spindles. Closer to a thousand bucks, cumulative, being the BEST I could find, used. Not the cheapest.

Present Swiss owner, Fischer Spindle, get around $1,500 and up for the proper rebuild and balance, even at a much lower RPM.

Good luck at thirty five dollars worth of used and abused Chinesium.

But you might be money ahead to buy a lottery ticket?

Or even just a porno magazine, flavour of yer choice, and a packet of Kleenex?

:D
 








 
Back
Top