More VSD/VFD problems.

[Ironwood]

My lathe rebuild has been dormant for quite a while now, due to other commitments. But just recently some problems became evident when I started playing around with the VSD.

http://www.woodworkforums.com/attachments/f65/181724d1315956479t-saj-vsd-problems-img_0677.jpg (http://www.woodworkforums.com/attachments/f65/181724d1315956479-saj-vsd-problems-img_0677.jpg)
http://www.fennecmachinery.com.au/SAJ%208000-M%20manual.pdf

I had run it up a few times without issue just after I got it, but recently I ran the autotuning function, this has set the overload cutout at 4.7 amps ( the motor plate is stamped 4.7 amps ).
Now it has become obvious that the motor is drawing a lot of current, because it cuts out on overload when the load is increased. It would be impossible to take even a light cut with the lathe.

I have measured the current with a clampmeter, and also checked it on the digital readout on the VSD.
With the belts off, the motor is drawing 3.2amps at 50hz, and 1.5amps at 100hz.

With the belts on, at 10hz its drawing 1.9amps and steadily increases to 4.7amps at 100hz, where it cuts out on overload. It will cut out earlier if you turn the dial up too quickly.
I have backed off the bearing preload to make sure it wasnt too tight, everything seems to turn over OK.

I have reset the maximum current back to 100 percent (which is 7amps) the motor still draws the same current, but doesnt cut out.

The VSD is drawing 6amps from the 240v supply just when it cuts out on OL ( at 4.7amps at the motor).

I recently had a mate who is an Electrician call in for a look. He tested the motor, all the windings have the same low resistance.
He ran a series of tests to make sure the wires were hooked up in delta correctly.
We ran out of time and he had to go, so we didnt resolve the problem.
He is quite sure the motor is all OK, and he suspects its a setting on the VSD.

Does anyone know what could be causing this ?


Should I be expecting to get a constant 240v at the motor at all Hz settings.
Its a bit hard to get a good reading with a digital meter as its fluctuating a fair bit.

[RayG]

Hi Ironwood,

Not sure exactly what it is you are asking, the 4.7 amp motor nameplate rating would possibly be for 415V (star) operation, 240V (delta)operation the current would be higher.

In answer to the other question..
The voltage at the motor terminals will vary depending on frequency, and what control mode has been selected... Have you selected Vector Control? (Function Code F067=3)

Regards
Ray

PS.. Not too sure what auto-tuning would be changing, I'll have another look at the manual you linked to..

EDIT: What values have you currently got for F068 (vector voltage compensation) and F069 (slip compensation co-oefficient) ?

[Ironwood]

Hi Ray, when the autotuning does its thing, it automically sets it to Vector control.

The 4.7 A stamp is straight after the 240 delta stamping.

[Cliff Rogers]

Check your mains voltage.... if it is coming in low then you will drag more current for the same power.

Power = Voltage x Current

Power/Voltage = Current

[RayG]

Hi Ironwood,

Just so, I'm not misunderstanding the motor nameplate, what is the kW (or hp) rating of the motor?

Regards
Ray

[Ironwood]

Ray , it is 1.1 KW. The VSD is rated at 1.5 KW, I would have thought it would be ample for the the motor.
The motor plate is also stamped class F, if that means anything to you.

[Ironwood]

Check you mains voltage.... if it is coming in low then you will drag more current for the same power.

Power = Voltage x Current

Power/Voltage = Current

No worries Cliff, I havent checked that. Will test when I am back down at the shed.

I have a plague of Marchflies at the moment, so havent been staying down there too long at a time :(.

[RayG]

Ray , it is 1.1 KW. The VSD is rated at 1.5 KW, I would have thought it would be ample for the the motor.
The motor plate is also stamped class F, if that means anything to you.

Hi Ironwood,

Ok, that all makes sense, 4.7 amps would be about right for 1.1 KW.

I think it's screwed up the auto-tuning, I'd start with reducing the torque boost setting (F009) and you should see a reduction in the current.

Regards
Ray

PS Buy a can of Aeroguard.. :)

[azzrock]

mate is that 100hz bit right. this sounds way to muck.
if this is a normal 3 ph motor. 50 hz should be the high end maybe 60hz.
100hz would be twice the normal rating.
im no expert and im experiencing my own vfd problem but the way i understand it stick 50 hz

[Ironwood]

Hi Ironwood,

Ok, that all makes sense, 4.7 amps would be about right for 1.1 KW.

I think it's screwed up the auto-tuning, I'd start with reducing the torque boost setting (F009) and you should see a reduction in the current.

Regards
Ray

PS Buy a can of Aeroguard.. :)

Hi Ray, I havent checked what F009 is set at now. If it is still at 3 percent ( factory setting) would you suggest to lower it ?

I bought a new can of Aerogard this morning, broke the nozzle on the old can yesterday :-.


mate is that 100hz bit right. this sounds way to muck.
if this is a normal 3 ph motor. 50 hz should be the high end maybe 60hz.
100hz would be twice the normal rating.
im no expert and im experiencing my own vfd problem but the way i understand it stick 50 hz

From what I have read, it is common for people to set the max. Hz higher than 50Hz when fitting a VFD, to get a higher top speed.
The 4 pole motors have a top speed of 1440 rpm at 50 Hz, I have been told they are using the same bearings as a 2 pole which is 2880 rpm at 50 Hz. So from what I have been led to believe, they can handle the higher speed.

Someone please correct me if I am wrong here.

[Ironwood]

Check your mains voltage.... if it is coming in low then you will drag more current for the same power.

Power = Voltage x Current

Power/Voltage = Current

Just checked Cliff, 242 volts at the VSD terminals while the motor is running at a slow speed.

Had to check this while jogging on the spot, to keep the Marchies off my legs :C

[Bryan]

Ah, Queensland - humid one day, pestilent the next. :)

[Ironwood]

Ah, Queensland - humid one day, pestilent the next. :)


Wouldnt live anywhere else :U

[RayG]

Hi Ray, I havent checked what F009 is set at now. If it is still at 3 percent ( factory setting) would you suggest to lower it ?

No, if it's still at 3% leave it, but I think you'll find that the auto-tuning has set it to a higher % :)



I bought a new can of Aerogard this morning, broke the nozzle on the old can yesterday :-.

Jog Faster... :D



From what I have read, it is common for people to set the max. Hz higher than 50Hz when fitting a VFD, to get a higher top speed.
The 4 pole motors have a top speed of 1440 rpm at 50 Hz, I have been told they are using the same bearings as a 2 pole which is 2880 rpm at 50 Hz. So from what I have been led to believe, they can handle the higher speed.

Someone please correct me if I am wrong here.


Yes, that's all good, the only issue might be that the power might drop away above 50 Hz..

Just as an experiment, you could drop F009 back to 3% and switch back to V/F mode (F067=1) and see if the current goes back to what you were seeing originally.

But, switching back to V/F mode, that's not really using the drive to it's potential.

Regards
Ray

[Ironwood]

Thanks Ray, I will check on F009 tomorrow. SWMBO has ruled we are off to the Harbour for Fish & Chips .

[azzrock]

your probably right. had not thought of it like that. what about the machine the motor is running at twice the speed. probably ok for a short time as well.
do you loose much torque at over 50hz


Hi Ray, I havent checked what F009 is set at now. If it is still at 3 percent ( factory setting) would you suggest to lower it ?

I bought a new can of Aerogard this morning, broke the nozzle on the old can yesterday :-.



From what I have read, it is common for people to set the max. Hz higher than 50Hz when fitting a VFD, to get a higher top speed.
The 4 pole motors have a top speed of 1440 rpm at 50 Hz, I have been told they are using the same bearings as a 2 pole which is 2880 rpm at 50 Hz. So from what I have been led to believe, they can handle the higher speed.

Someone please correct me if I am wrong here.

[Cliff Rogers]

Just checked Cliff, 242 volts at the VSD terminals while the motor is running at a slow speed....
OK, cross that one off the list.

[tanii51]

i had a similar problem using an elcheapo chinese vfd if you set the motor amps at what the name plate( 1 .4 amps) said it would cut out with just a light cut .some where i read you should raise the motor current to a higher value which i did (5amps)and it fixed the problem .A very heavy cut only brings the current up to about 4.4 amps. it doesnt seem to have had any bad effects on the motor or vfd nothing gets overly warm
john
hmm i wonder if wired in delta config the amps should read 3 times the rated in star mode( 3x1.4=4.2)

[Ironwood]

your probably right. had not thought of it like that. what about the machine the motor is running at twice the speed. probably ok for a short time as well.
do you loose much torque at over 50hz

My lathe has a tapered roller bearing headstock, I am pretty sure it can run at high speeds for long periods of time.
I guess you will have to make a call on your own machine, taking its design and condition into mind.

I am not expecting to lose much torque at the Hz range I have set on the VFD.
My VFD has vector control so I am hoping for good torque through a wide Hz range.
From what I have read, I will lose torque at very low Hz, and also very high Hz.

[bonox]

Power = Voltage x Current

Power/Voltage = Current

actually there's a power factor correction in there as well, which for a motor running outside it's nameplate range could be quite low.

If the motor is working at a power factor of less than about 0.7, a 1.1kW motor will overload a 1.5kW supply.

[eskimo]

3.2amp no load seems too high

How did you measure the voltage at motor terminals?...to terminal-earth or across each phase?

did you measure all three phase current draws?

Have you put a megger on the motor to ensure it doesnt have any leakage to earth?

(I assume your using a 240 single phase to 240v - 3 phase vsd.)

[Ironwood]

Just as an experiment, you could drop F009 back to 3% and switch back to V/F mode (F067=1) and see if the current goes back to what you were seeing originally.

But, switching back to V/F mode, that's not really using the drive to it's potential.

Regards
Ray

Checked the F009, it was set on 5. Set it back to 3, and ran the motor, it was an improvement, but still cut out on OL. I changed it back to 2, still cut out on OL when running at high speed.

I changed back to V/F mode, that didnt seem to change the current at all, it still cut out on OL.

I checked F068 ( vector voltage compensation) it has been set at 5 by the autotuning.


F084 (power supply voltage) is factory set at 220 , I had never changed this before, but I set it to 240 today.
This didnt seem to improve things.

[Ironwood]

i had a similar problem using an elcheapo chinese vfd if you set the motor amps at what the name plate( 1 .4 amps) said it would cut out with just a light cut .some where i read you should raise the motor current to a higher value which i did (5amps)and it fixed the problem .A very heavy cut only brings the current up to about 4.4 amps. it doesnt seem to have had any bad effects on the motor or vfd nothing gets overly warm
john
hmm i wonder if wired in delta config the amps should read 3 times the rated in star mode( 3x1.4=4.2)

I might have to try this also, before I did the autotuning, the problem wasnt evident.

[Ironwood]

3.2amp no load seems too high

How did you measure the voltage at motor terminals?...to terminal-earth or across each phase?

My Lecky mate was doing the testing while I operated the VSD, so I am not sure, but will check with him.


did you measure all three phase current draws?
I remember him mentioning that all 3 phases were high, so I think he must have.


Have you put a megger on the motor to ensure it doesnt have any leakage to earth?

(I assume your using a 240 single phase to 240v - 3 phase vsd.)
A different Lecky mate tested the motor with his megger before I fitted it to the lathe. He said it was all good.

The VSD is single phase to 220/240 3 phase. It was factory set at 220V supply, I changed it to 240V today.

[RayG]

Hi Ironwood,

Not sure how easy it's going to be to try and figure out what the auto-tuning function has changed.

Just checking...what values are entered for the number of poles F52, and of course.. the ratio of inverter rated current to motor rated current F78.

Also while we are digging around, if you have time while dodging march flies..:)

F1: acceleration time
F2: deceleration time
F10: rated frequency of motor (factory setting: 50Hz)
F15 upper limit frequency

F11 rated voltage % of motor

F67: Operation Mode
F68: vector voltage compensation
F69: Slip compensation



If all else fails... the next step... :rolleyes:

It's a drastic step, but it might be quicker to just reset the drive to factory defaults and re-commission it with the settings you originally entered.


Regards
Ray

[azzrock]

My lathe has a tapered roller bearing headstock, I am pretty sure it can run at high speeds for long periods of time.
I guess you will have to make a call on your own machine, taking its design and condition into mind.

.

ya tapered bearing head stock. that's great so does one of mine.
i just get concerned about the rest of the bearings in the machine. there is more than one shaft to worry about. are all the bearings in the head stock and feed box ect roller bearings? what sort of machine is it and why didn't they make it run twice as fast as they did.? i run my machine faster than the factory designed it but not for long and not more than 15 percent.. just interested because im setting one up as well.
aaron
.

[Ironwood]

Hi Ironwood,

Not sure how easy it's going to be to try and figure out what the auto-tuning function has changed.

Just checking...what values are entered for the number of poles F52, and of course.. the ratio of inverter rated current to motor rated current F78.

Also while we are digging around, if you have time while dodging march flies..:)

F1: acceleration time
F2: deceleration time
F10: rated frequency of motor (factory setting: 50Hz)
F15 upper limit frequency

F11 rated voltage % of motor

F67: Operation Mode
F68: vector voltage compensation
F69: Slip compensation



If all else fails... the next step... :rolleyes:

It's a drastic step, but it might be quicker to just reset the drive to factory defaults and re-commission it with the settings you originally entered.


Regards
Ray

Hi Ray, I will try to answer all your questions I can, without going back down to the shed.
F52 - I havent changed this, so assume its still on factory setting of 4 (its a 4 pole motor by the way)
F78 - I have set this to 55, my calculations are 4.7 is 55 percent of 7 (am I on the right track here?)

F1 - I have set to 3
F2 - I have set to 2
F10 - left at 50
F11 - 100
F67 - autotuning has set this to 3 ( I have tried resetting back to 1, but the high current draw continues )
F68 - autotuning has set this to 5
F69 - I havent checked this one, will look tomorrow.

Regarding the resetting the factory defaults, I have decided I will go down that path when I get home from work tomorrow. This problem wasnt evident before I did the autotuning.
I dont know what the current was before I did the autotuning, as I only started to check once the lathe was cutting out on OL.

I have reset F51 back to 10 seconds, I think autotuning set it to 30. Before it cuts out after 10 seconds above 4.7 amps, the current does go up above 6 amps if the pot. is turned up quickly.

[RayG]

F78 - I have set this to 55, my calculations are 4.7 is 55 percent of 7 (am I on the right track here?)


I would have gone for 70% rounded up from (4.7/7)*100 = 67

Regards
Ray

[Ironwood]

I would have gone for 70% rounded up from (4.7/7)*100 = 67

Regards
Ray

No worries, so that could be causing, or contributing to the problem.

Should have gone looking for that calculator instead of figuring it out in my head :-

[RayG]

Hi Ironwood,

Well it could possibly be the problem, using 55% you would be effectively setting the rated motor current to 3.85 amps. instead of 4.7 amps

So you will get instantaneous trip at 5.8 amps instead of 7.4 amps, that might do it.

That's assuming I'm reading page 8 of the manual correctly. :rolleyes:


The whole purpose of this protection, is just to protect the motor, from overcurrent, i would leave F51 at 30 seconds.

The other thing I meant to ask, and that is, when it trips what is the exact error number?

Regards
Ray

[jhovel]

Not sure if this is helpful: my view and understanding is that the powersupply can't increase the voltage. Therefore, the motor will draw whatever current it needs to run - up to its capacity - no matter what the nametag says.
Electric motors can run above their rated capacity for a while but get hot in the process. So I have set my VFDs at THEIR capacity and keep an eye on the motor temperatures. If it goes higher than it should, there is a problem with the motor, not the VFD. It would run just as hot if you had a 3-phase supply without a VFD.
One of my motors got very hot very quickly for no obvious reason an while back and it turned out to be a damaged grease seal rubbing on the shaft. Like you, I was worried it was related to the VFD... turned out it had nothing to do with it....

By the way, all my three phase motors will run at significantly higher frequency and speed than designed for - most will run at 125Hz perfectly. I found that all have a frequency at which they slow down again, probably due to magnetic flux slip which produces a braking action. In all motors tested that was around 200Hz - the bigger motors lower than the smaller ones. I've run my big old milling machine 2HP motor for hours at 100Hz without any thermal or other issues.

Joe

[RayG]

Not sure if this is helpful: my view and understanding is that the powersupply can't increase the voltage. Therefore, the motor will draw whatever current it needs to run - up to its capacity - no matter what the nametag says.
Joe

Hi Joe,
Not quite.... with VFD's the current is controlled by how hard you drive the IGBT's, and this effectively changes the voltage. (no it can't increase the voltage, beyond what the DC bus will allow for) :)

In a simple V/F drive, the voltage varies with frequency, up to 50hz, and then flattens out at whatever the maximum is, so beyond 50Hz on a V/F drive torque starts dropping.
To help with starting at low Hz, VF drives increase the voltage at low Hz, called torque boost by most manufacturers..

On a vector drive (like the one Ironwood has) the VFD does calculations about what proportion of the current is doing various things, part of the current produces the magnetic field, (the magnetizing current) and 90 degrees out of phase with this, is the torque producing current. The magnetizing current drops away when you get above 50hz, a bit like the V/F drives do.

There are different types of vector drive.. this one, is a sensorless vector vfd, probably with a V/F core..

Sorry, getting carried away, I'll stop now.... :D

Regards
Ray

[Ironwood]

I have had something come up unexpectedly, I cant see I'll get time to look at the lathe until the weekend.
Hopefully Saturday afternoon I'll do the reset to factory settings, and see what happens then.

[Ironwood]

Well I got some spare time sooner than I thought.
Had a spare hour or so today, so I did the reset to factory settings as per the manual.
After it did its thing I went through each parameter and checked to see it was the same as the factory setting in the manual, there were a few that didnt change back, so I did them manually.

I ran it up, the high current was still a problem, just wasnt cutting out. With all the belts on, and driving the spindle, it was getting up to 7 amps when turned up to 100 Hz.

I have a 1hp motor that I replaced with a single phase motor, out of a Durden Jointer, it is 2 pole so I changed the setting on the vfd to reflect this, I hooked it up in delta and hooked up the vfd to it.
It was drawing less than 2 amps with no load, I just put the sole of my boot on the pulley to provide a bit of load. When enough pressure was applied to start slowing down the motor, the amps started to rise, the current was getting up to 5 or 6 amps quite easily.

I dont know where to go with this next. Is it possible that the VFD is faulty ?

[RayG]

I ran it up, the high current was still a problem, just wasnt cutting out. With all the belts on, and driving the spindle, it was getting up to 7 amps when turned up to 100 Hz.

dont know where to go with this next. Is it possible that the VFD is faulty ?

Hi Ironwood,
That sounds ok, I think it's only supposed to trip if it's overcurrent by 150% for 30 (or whatever F51 value is) seconds.

I thought the problem was it was tripping on overcurrent, now, the problem is it's not tripping? Or have I misunderstood something?

The motor should handle moderate overcurrent without problems. You could check the motor specs to see what the locked rotor current is, but I'm pretty sure it will be more than 7amps...

Regards
Ray

[eskimo]

Hi Ironwood,
That sounds ok, I think it's only supposed to trip if it's overcurrent by 150% for 30 (or whatever F51 value is) seconds.

I thought the problem was it was tripping on overcurrent, now, the problem is it's not tripping? Or have I misunderstood something?

The motor should handle moderate overcurrent without problems. You could check the motor specs to see what the locked rotor current is, but I'm pretty sure it will be more than 7amps...

Regards
Ray

LRA should be around 6-7 times FLA

LRA = Locked rotor amps
FLA = Full load amps

[Ironwood]

Well I have had a breakthrough today.:2tsup:
I hooked the 1.5hp motor back up to the Vfd, but I used a different piece of cable, I had thought a couple of times to try a different cable, but always dismissed it.
The old cable is the original one when the motor was driving a pump. Maybe has some broken strands or something internally :?.

Now I am getting about 2.8 to 3 amps at all Hz settings, it gets up to 5 amps briefly when accelerating up to speed ( 3 second acceleration time ).

Still maybe a bit high, but I am happy to at last have some light at the end of the tunnel.
Next step will be to do the autotuning over again, and see what happens this time when the Vector control is turned back on.

[RayG]

Hi Ironwood,

That's interesting, sounds like you are on the right track. Do you have any pictures of the two different cables?

Regards
Ray

[Ironwood]

Hi Ironwood,

That's interesting, sounds like you are on the right track. Do you have any pictures of the two different cables?

Regards
Ray

I dont have any pics on hand, but I can take a couple tomorrow if you like.
There is not much to see really, the old cable is just a purpose made one, four wires fed through a piece of thick flexible conduit.
I will pull them out and inspect them now that I am not going to be using it.

The new cable is very temporary, it is a new piece of 3-core, with a single wire running beside it to make up the extra needed.
I will buy a new piece of 4 core cable tomorrow when I go in to town.

[RayG]

Hi Ironwood,

One other question, what sort of cable length are we talking about.

The reason I ask, is that the leakage capacitance would have to be pretty high to cause the sort of current increase you've been seeing.. which would usually mean long cables, and there are other issues that can occur with long cable runs on VFD's, pulse ringing and and sometimes overvoltage spikes which can damage motor insulation.

The shorter the better, under normal circumstances.

With the old cable I wonder if insulation breakdown at high voltage might be the problem with the old cables? A megger test might be interesting.

In any event, some 3 core plus earth orange circ is what you need to get :)

Regards
Ray

[Ironwood]

Ray, the old cable is just under 1.5 meters long, the new one is about 1 meter long.

The manual mentions 15 meters being too long.

To run from where I want to mount the VFD to the motor, I will need about 1.2 meters of cable.
Now that I know that its going to work, I can start to mount things in position and run some permanent wiring to switches etc.

[eskimo]

A megger test might be interesting.



you took the words out of mouth Ray

sounds like insulation breakdown between wires????

and who would have picked that ...ME...I mean I should have thought of it..I had this exact problem about 2 months ago..

The client said the pump was crook..(a 10hp motor mind you) its tripping the breaker...can you take it out and get it repaired...no problemos said I..rip it out (without checking) take it to motor rewinders who rang the next day and said...there's nothing wrong with except for the a noisy bearing...OK replace it...err them..????

...what is going on here...checked out the control circuit ..all ok ...contactor checked out ok..megger tested wiring to isolator..ok...what now mmm????, megger test wiring from isolator to motor...what!!!???? its 20 megohms?

[Ironwood]

I pulled the wires out of the old conduit last night when I got home.
I was expecting to see the insulation cracked or worn. It all looked good except for a couple of spots where they were rubbing together and formed small grooves in the insulation, but it doesnt go all the way through, I have bent the wires tightly on those spots to see if I could see the copper anywhere, but it all looks good.
Maybe the problem is too small to see by my poor eyes.

[eskimo]

wonder if you may have had dust/dirt etc on the terminal plate of the motor which was causing some leakage?

[Ironwood]

wonder if you may have had dust/dirt etc on the terminal plate of the motor which was causing some leakage?

Well I wouldnt rule it out, but it looks pretty clean to me.

I hope to get into town today so I can get a short length of cable so I can start to make things a bit more permanent.
Everything is hooked up temporary at the moment, while I try and get to work satisfactorily.
Once I get the permanent wiring done, I will run the autotuning again.
Should be a better result this time hopefully.

[Ironwood]

I got a short length of cable from in town the other day, got it all hooked up, ran OK.

I ran the autotuning again today, The current gets slightly higher than before I ran it, but only at high Hz settings. Once the lathe has run for a bit and warmed up, the amps range from 3 amps through most of the range, to 4.5 amps at 95 -100 Hz. While its cold, running at 95 - 100 Hz it can get up to 7 amps. If it becomes a problem I will set it to 95 Hz maximum.

With the belt on the middle pulleys I get a spindle speed range of about 30 rpm to 1200 rpm, I envisage being able to do most, if not all of my work on this ratio. I will see if it has enough torque through the full speed range once I get a bit more progressed. Maybe will have to change down to slower ratios for the big stuff.

I put some stainless bar ( its what was the first thing I found, so it got used ) in the chuck and took a few fairly light cuts, the current wasnt increasing at all while doing this. Things are looking good :2tsup: