Keling VFD and 2.2 Water cooled speed not tracking properly

[dfmiller]

I have posted a couple other spots on the web but no bites so I will post here also.
Sorry for the cross post.
I have a G540 hooked up to a Keling (HY) VFD.
The speed is not linear.
The Input voltage measured at the VFD is shown on the graph as Vout and it is linear.
The speed Top speed and lowest speed are good.
Current setting for the first few paramters.
PD000 0
PD001 1
PD002 0
PD003 400
PD004 400
PD005 400
PD006 2.5
PD007 0.500
PD008 220
PD009 13.0
PD010 6.5
PD012 133
PD013 0
PD014 5.0
PD015 5.0
PD016 5.0
PD017 5.0
PD018 40.0
PD019 40.0
PD020 80.0
PD021 80.0
PD022 0
PD023 1

PD141 220
PD142 11.0
PD143 2
PD144 1440


Thanks
Dave

[mike_Kilroy]

ok i'l bite. how bout this: u r assuming 0v shud be 8krpm, how bout assume 0v is 0rpm instead? yes, u have min spd set to 8krpm; assume any command less than 8krpm will be ignored and u will go instead min spd or 8krpm.

looks like this assumption matches your imperical data. I will post this then add MY assumption line for command to see....

[mike_Kilroy]

setpoint 0.....2.4k..... 6k..... 12k....... 16.8k........ 24k
Vout .....0.......1........ 2.5 .....5......... 7.5.......... 10
actual ..8k.....8k....... 8k..... 11.6k..... 14.5k...... 24k

seems to work. looks to me like this is the reason you are confused?

[dfmiller]

Mike anything is possible.
But I think setting the minimum to 6K and 8K and the lower speed following the setpoint means that 0V maps to the Point set in PD011.
I will have a go at your numbers.
Thanks for your thought and time.
Its the first time messed with a VFD so I am sure its my confusion.
Thanks
Dave

[mike_Kilroy]

Originally Posted by dfmiller ....But I think setting the minimum to 6K and 8K and the lower speed following the setpoint means that 0V maps to the Point set in PD011..... Dave

good luck. I know nothing about that brand of vfd; we work with hitachi.

just thought I would throw something out there to get the ball rolling!

I am not sure what you mean by your sentence above. seemed from your numbers you got NO speed change until your Vout command hit the linear point on a 0 to 24krpm = 0 to 10v command line...... so no change from the min 8krpm until the command got upto (8/24)*10v=3.3v just like your imperical data shows, no?

u got 8.7krpm with - now I cant see back to see but like 3.8v command? doing the math, 8.7/24 * 10v= 3.6v command. isnt that where you started to get speed increase? seems like this math matches your results pretty good for a low cost vfd.

[dfmiller]

Mike,
You might be on to something here.
My basic assumptions were you could set a mapping of the analog input where 0V DC input mapped to whatever RPM was set in PD011 which is minimum frequency.
Then as you increase your input voltage the speed will increase.
I most likely am expecting the VFD to operate wrong.
I need to find another manual to see how things are explained there. do you know where I can find a Hitachi manual? There are a few holes in the manual I have.

I can set the min frequency back to small number and see how it works.

Since it sounds like you know can you answer m other questions.
Why on a Water cooled spindle do they say minimum RPM is 8K? I understand on a Air cooled it might be because at lower RPM the fan does not work. The vendor has not come up with any reason. There are a few other mistakes in his documentation so I really don't believe it.

I have chatted with a couple of other people and they cant explain any reason.
Thanks
Dave

[dfmiller]

Mike,
I am happy to report I have found and fixed the issues.
If I set PD073 to 133 it works as expected. 133hz is 8000 RPM
PD073 is titled Lower Analog Frequency. It seems to you have to set both PD011 and PD073 to make it work.
Thanks for your help.
Dave

[mike_Kilroy]

glad u got it! ya, hitachi has a couple parameters also to set actual min speed and then another to set min speed point on speed pot so you wud not get that dead bottom 1/4 of pot too.

8k min has NOTHING to do with water vs air cooling. it is no different than a regular ac motor say rated 1800rpm. you can do upto about 2x base speed max and you can do down to around 1/6 with some torque and below that it gets hot - but also has no HP left.... same with a HI speed motor.

but in reality you dont get much use as a spindle below about 1/2 base speed: remember, 1/2 base speed = 1/2 hp rating there.... so not many people machine below 1/2 to 1/3 the base speed..... with that picture in mind.....

what is your base speed? doubt if you set it on your vfd - so u just set it by default at 24k rpm! bet i'm right? u have 230v and 24krpm as base speed - most of you guys do that. simple to do. cheap drives really can't set any better than that. so consider: 24k base, down to 1/3 is about all the usefull speed you can use - hence 8k!

but there is more to it that even this! some folks reading this will say time out - I machine below 1/3 speed on my 1800rpm spindle..... true but now we get back to your wrong vfd setting calling 24k base speed! your spindle is likely a 2 pole induction motor. that means base speed IS 3600rpm! so if the mfgr called it base speed as normal, you could only go to about 7200 rpm max before the motor cant put out torque anymore...... so how to get to 24kprm on that 3600rpm motor??

artificially set the real base speed VOLTAGE low; so your real 3600rpm base speed real rated voltage is way lower than normal - that way the voltage can continue to increase above real base speed and you can keep going up in speed. gets a bit complex, but the net result is when you turn down the speed on your high speed spindle motor, you are cutting the voltage way lower than it needs to run along a constant v/hz curve so the torque goes down as speed goes down, unlike the regular motor that has constant torque from base speed to 0. so by the time you get down to 8k you no longer even have the torque rating at 24krpm so it is basically 1/4hp rating due to speed going down TIMES probably 1/4 torque rating so only 1/16th HP rating left! not worth even trying to run slow.

experiment to prove it to yourself if you want: set min speed back to 0, run it 100rpm and if it were on proper v/hz curve it would still have nameplate rated torque - it wont - u'll be able to stop it very easy - near zero torque available I'll guess.

we do high speed high performance large hp spindle systems and use fancy vfds where we actually set base speed properly and yet still allow the voltage to keep increasing above base speed to max available and thus can make this 24k spindle provide constant torque down to probably around 4500rpm (where YOU are probably getting 1/10th rated torque). but you would not want to pay the $ 3000 for this drive for your motor and you probably would not use it at these lower speeds anyway.

sorry for rambling but I enjoy this topic

[dfmiller]

Mike,
Thanks for the detailed explanation. I followed most of it. I need to do some more reading on induction motors;-) I am a MET that's been doing electronics since I graduated in the 80's. I am finding learning is harder than it used to be. I know have to read things more than once.
In my application the spindle is over-sized. I could not understand why the speed was limited but now I get it. So a so called Vector drive would improve the low end torque some? Not that I need it for now.
Sounds like you have a fun job. And you enjoy it. That great.

I appreciate your time. Its nice to chat with someone that has a full understanding of the topic. I love to understand what I am messing with. That's the kind of person I am. Bit by bit I learn.
Thanks
Dave

[mike_Kilroy]

you sound like me

Actually a REAL vector drive DOES get around the issue of output voltage since it controls current only and whatever voltage is required happens; so one COULD tell it like your spindle the REAL base speed (prob 55rpm or so) where it gets to 230v and then you get much more torque. Another thread had a similar discussion and the guy could not get real motor data from the chinese spindle mfgr - I dont think THEY knew how it really worked!

[dfmiller]

I imagine that someone actually knows but the many layers of sales agents makes it impossible to talk to the people in the know.
That happens here in NA also. I have been on both ends of that, so many companies want to prevent the end customer from talking to the people who designed and understand the product. I think that was why I am no longer working for the large US company I was working for. They did not like my small team of people that produced. The bought us up and effectively shelved the technology. It seems a waste to me.

They did not think it was appropriate that the chief architect ( Used to have the lofty title of CTO) was out making sales calls.

So glad I am out of that now. It did not suit me.

Thanks
Dave