Testing The VFD, Break Resistor and Wiring to AXBBE

[Phil Mayor]

Hi everyone,

So I've had the electrician round and had my Electrics upgraded, so I now have a Single Phase 32a Soccket, I'm doing bench testing and got the VFD and Spindle turning on/off (through the VFD Control Panel) and I've been able to program some of the Parameters of the VFD, but there are lots and I'm not 100% clear what some do.

Firstly I got a seperate Breaking Resistor (1kw, 60ohm) the VFD Manual says it can be wired up 2 ways - either connect the resistor to DC+ and R-, or to R+ and R-) I've done both these methods but when I stop the spindle it just slowly comes to a stop as it does without the resistor connected... I've changed the Parameters in the VFD that I found related to breaking but there's no change in stopping time, I would need this eventually as I want to utilise the ATC function and have it stop quickly (within 6sec so it can then do the tool change)

The break parameters I changed are -

Page 41
1_06 Starting DC Breaking time
1_07 Stopo Mode - Changed to 2
1_08 Stop DC Breaking starting speed - changed to 3000rpm (although I don't entirely understand this)
1_10 Stop DC Breaking time - changed to 6sec

Page 46
1_30 - Break Utilisation rate - changed to 5, but not sure if this should be higher or lower..??
1_32 - Break Resistance Tolerance - set to 60ohm as my Breaking Resistor Specs
1_33 - Break Power Resistance - set to 1000w (1kw) as my Breaking Resistor Specs

link to manual

https://www.manualslib.com/products/Dema-Electric-D6-Series-4142539.html


I would also love to connect this up to AXBBE so I can turn it on/off and set speed through the UCCNC Software I have seen a lot of wiring diagrams on how to do it but my issue is my VFD has differently labelled terminals so I'm not confident enough to try this without help/input form here, hopefully.

The control Terminals can be found on Page 17 link above

To change Spindle Speed through UCCNC I believe I would need to

connect

AXBBE AO1 to VFD GND (I suspect this is any ground terminal, I can see 2??)
AXBBE 5V0 to VFD AI1

To turn Spindle on/off through UCCNC I believe I would need to

connect

AXBBE 24V+ to Relay +
AXBBE Isolated output 2 to Relay -

but then I'm not sure which terminals on the VFD I go to from the Relay

I've also not seen anywhere in the VFD the parameter to say I want to control this through other software...??

I would be so grateful for any help or input on any of these issues,
Sorry for the long post

Cheers,


Phil

[Muzzer]

Wonderful Chinglish!

There are 2 different braking mechanisms here.

The "DC braking" type drives a DC current in the motor windings. This is rather like driving the motor with a fixed (rather than rotating) field and it causes a drag torque on the rotor. It's not particularly good for the motor, since it results in all of the energy being dumped in the rotor or the motor. There is usually a set point for the braking current and a speed at which it starts to be applied. It can also be used to stop the motor spinning under an external torque (not a problem here). Generally for motors, the torque generated is proportional to the current. That's true for current injection too. You can increase the current to as much as 150% of the rated phase current but that's probably not ideal. There is a delay tikme before the current injection is started and the duration of the current injection seems to be a fixed duration which may continue after the motor has come to rest.

The "braking resistor" scheme simply limits the maximum voltage on the internal circuit. When you decelerate the motor rapidly, the energy is dumped back into the VFD's internal high voltage storage capacitors. If the inertial energy is sufficient and you decelerate quickly enough (so that the energy is not consumed in the VFD by internal losses), the internal voltage could rise to the point where the VFD is damaged, although the VFD will protect itself against overvoltage damage by triggering an "overvoltage fault" and disabling the output (which results in the motor simply spinning down at its own right). Without a braking resistor, you have no choice but to limit the deceleration and if you have that set too aggressively you will see that overvoltage fault. When you fit a braking resistor, the VFD can dump any excess energy into it. This allows you to decelerate at a faster rate than you could using the FD on its own.

The "braking power resistance" is the peak power rating of the braking resistor. If you have a "proper" braking resistor, it will have a specified peak power rating (in Watts) - yours appears to be 60R (01_32) and 1000W (01_33). The "braking unit used" (01_31) is the voltage threshold at which the braking resistor will start to be used - 720V seems a bit high for a 240V input VFD - for a single phase VFD I would expect that to be closer to 450Vdc. If the internal voltage never rises to this level, the braking resistor won't be doing anything. If you shorten the decel time, you should find that eventually the braking resistor will start to have a noticeable effect. Equally, if you have braking resistor turned off, you will find that shortening the decel time will result in an overvoltage fault.

A decel time of 6 seconds is pretty slow unless you have a large inertial load. I'd suggest you try shortening it down to something closer to 1 second or so. You should then find that the braking resistor actually does something. It may start to warm up slightly after a few stops from high speed - that way you can tell it's being used, if you don't have any test equipment to tell you otherwise.

Some VFDs will allow you to use both DC current injection ("DC braking" here) AND a braking resistor but they work in different ways anyhow. However, for this product, 01_07 seems to require you to choose one or the other. If you have a braking resistor you might as well make use of it.

Hope that helps a bit.

[Muzzer]

For the control wiring, you also want to look at page 13.

- Pins AI1 - AI3 (page 17) are the analog inputs for your 0-10V speed signal - unless you can generate a +/-10V signal you should use AI3. There's also a 10V supply on "10V" if you need to provide that to your controller or want to use an external potentiometer.
- The "multiple functional digital inputs" G24 and X1 - X8 are used for the "enable", "direction" or "FWD" / "REV" signals from your controller. You have to tell the VFD what functions you are wanting for those. The various schemes are shown on page 55 and 56 (their page numbers).
- Some VFDs have an 24Vdc power supply inside the VFD but some don't, in which case you'd have to provide your own 24Vdc power supply. This product says it "offers the user" 24V at 150mA on pin "P24" / "XC", which keeps life simple. This is a safe low voltage output ie not connected to mains, as are the digital inputs and the 10V analog input.

[Phil Mayor]

Hi Muzzer,

Yeah, the Chinglish is whats confusing me, im obviously no expert in electrics anyway but coupled with the Chinglish it just makes it even harder to understand...

This is all brilliant, thank you for the detaild info, I will print this off and go through it as there's a lot to take in but thank you so much!

One point on the Control Woring, you mentioned using AI3 for the +/-10v but I don't think I have that terminal, I think that's part of the PG expansion terminal that is bought separately, if that's the case would I be able to use AI1 or AI2 terminals or not...?

Cheers again

Phil

[Muzzer]

I can't easily look right now but most VFDs have a 0-10V input, not +/-10V, so I'm a little surprised. It may be you can use either of those but equally, you probably can't generate that +/-10V output on your controller anyway. I was simply going on the table on one of the pages.

If I get a chance later, I will see what I can make out.

[Phil Mayor]

Hi Muzzer, theres no rush but thanks that would be great if you could....

With regards to the Break Resistor I've been doing a bit more reading and testing with the info you provided on the VFD Parameters and had some noticable results, however, still not close to where I would expect to be with break time and i'm getting close to the top end of all the parameteres, I think the main parameter causing me issues is the 01_08 'DC Break Starting Speed' I've got this set to 3000rpm which Is the most I can set it too, and sure enough when I stop the Spindle it slows down but it takes around 17s to get to 4000rpm then as it hits 3000rpm it stops dead - total time around 19s from 20,000rpm to 0rpm - I would of expected around half that time to be honest.... I could increase both the breaking current parameter a bit more, they're both at 100% at the min and it says I could go up to 150% I thunk

Cheers,

Phil

[Muzzer]

On this VFD you can't have both DC braking and braking resistor, as they are different mechanisms and you can only enable one or the other.

That "braking starting speed" threshold is only for DC injection, whereas decel will reduce the set speed regardless of whether DC braking is enabled. Have you also tried reducing the decel time? I suggest you firstly select the braking resistor option, then start to reduce the decel time. It should then work from any speed and you should be able to get the stop time down to a second or so. If you have the braking resistor connected and take the decel time down to the point where it overvoltage trips, you can then increase it a bit and you are likely as good as you will get. On page 110, the overvoltage fault during decel is displayed as "E.ouD".

The threshold voltage (720V) for braking resistor operation doesn't sound right for a single phase / 240V input VFD. The manual says "The biggest output voltage is the same with the input voltage" - and the maximum input voltage for these VFDs is quoted as "240V". That means the internal voltage would be ~340Vdc. I would expect the braking threshold to be closer to 400Vdc rather than 720Vdc. I expect it's already set to a ~400Vdc but if you get an overvoltage fault without any obvious braking, I'd check that parameter and reduce it if necessary.

What kind of machine is this? I am wondering what spindle inertia you will be seeing.

[Phil Mayor]

Hi again Muzzer,

The Threshold Voltage is the only Parameter I've not changed, this is set at 720v I was unsure what it did, so didn't want to mess with it... I can bring it down to closer to 400v and see if that helps...

I have seen something (Page 47) that states the most power allowed for is 5 times the 'Breaking Power Resistance' (01_33) which in my case would be 5kw but I was a bit worried to increase this setting by that much, but I could do it in small increments, maybe...??

I've changed the 01_14 - 'Decel time 1' to 4 seconds (this is as low as I can get it without Overvolt) and 01_16 - 'Decel time 2' to 0.5 of a second.

at the moment I'm still not seing any noticable reduction in stop times, I can see/hear the resistor kicking in, as soon as I hit stop but till it reaches 3000rpm it doesnt kick in fully...

I've also contacted the supplier, but they usually take a few days to reply...

It's a CNC Spindle Router, so there isn't a lot of inertia compared to something like a lathe.

Phil

[Muzzer]

You should be able to bring that to a stop fairly quickly.

Are you sure you have disabled DC braking and instead enabled the braking resistor? I wouldn't expect the braking resistor to hold off until you get down to 3000rpm. It doesn't care what the speed is, only that the internal DC voltage is trying to exceed that threshold value and needs to be kept in check. That voltage surge is due to trying to decelerate the spindle rapidly and regenerating the energy back into the inverter. Which is why the decel time and threshold voltage are the only parameters that really matter here. If the braking resistor mode isn't enabled, the only thing limiting the voltage is the losses in the drive. On the other hand, 5kW should fairly rapidly burn off the RPMs.

If it's a proper braking resistor, the 5X factor should be fine as long as the "1kW" figure is a continuous rating. Ultimately the limit is the melting point of the resistance element inside the resistor. They are made of wire or foil so they have a decent thermal mass. Other, more common resistors use carbon film which can't withstand much energy before burning out.

[Phil Mayor]

Yeah, I turned the DC Breaking off by selecting the 'Stop Mode' (01_07) and Changed from 2 to 0, the only difference I can see here is when it gets to 3000rpm it stops as before but rather than stop dead it rotates freely around 5 times and just comes to a stop, whereas when the DC Breaking is selected it just stops and seems to lock in place for a second or so...

I'm not sure if it's a proper breaking Resistor, I've never owned one before so I have nothing to compare it with, it had good reviews and was around £50.00 which was mid-range....

I've attached 2 videos one with DC Breaking and one without...



https://youtube.com/shorts/_icOR_oH6J0?feature=share


https://youtube.com/shorts/789Yqw6VrgQ?feature=share



Quick update

The Chinglish has confused me again here it's contradicting itself, I've just found a diagram that says the Break Resistor should be connected to DC+ and Db as far as I can see I don't have a Db terminal..??

32210

Also, found the ohms rating for this VFD (11kW) should be 50ohms I have a 60ohms Resistor... is this a possible issue that could be affecting the breaking time...???

32211

[Phil Mayor]

The supplier has just got back to me and suggested increasing the Break Resistor to a 1500w 75ohm type, but from my understanding a 75ohm would take even longerr to stop than my 1000w 60ohm one..?

[voyager1972]

I am following this post with interest as i am also in the middle of an upgrade to an atc spindle which i have mounted and have running from the potentiometer , i plan on using the manual tool change butoon until i get my head around the auto tool change setup ,i also have a braking mechanism which was part of the original setup with the old spindle .i love having a go at these things myself but i am finding it difficult to get information online ,so hopefully i can get some good advice on the forum , i am running uccnc with the uc300eth-5lpt and ucbb.

[Phil Mayor]

Hey Voyager,

I'm like you and also love having a go myself, I hope you can get some advice/info that will help your build, although I doubt it will be from me :apthy: Muzzer has been a great help so far and he has helped me get to the stage I'm at and understand how I got there, but unfortunately I still can't get past the final hurdle - I must have read the manual 4 or 5 times but I can't see any other Parameter that relates to Breaking, so I just don't know why it's not working as it should... I have thought maybe it's the VFD itself but it is breaking, just not enough, which then leads me to think it's a parameter that just needs tweaking....

[voyager1972]

the braking mechanism was setup on my old vfd , i will hook it up and go through the settings and see what i can find on the braking side , i am stuck with the manual tool change button , i want to connect it with two solenoids in line ,one connected to the button the other connected so that it is disabled when the spindle is running , i just dont know how to go about it ,i would like it to be safe ,i dont want a tool ejected during a cut , i upgraded my machine 2 years ago from a chinese controller to uccnc ,it took me a while but i got there in the end , i am not into the electrical side of things but i really enjoyed the whole process. then i purchased an atc spindle and vfd and that is where im at now.

[Phil Mayor]

Looks like a nice Spindle that mate, yeah any help would be appreciated thanks!! I know what you mean, I have attached a diagram that has come with my Spindle, it sounds like exactly what your describing, weather you've already got this or it helps I don't know...obviously it's a different Spindle but the same principals, I could send the whole document if you think it helps..??

32216

Also just remembered I watched a YouTube a few weeks back and Clogh42 has a video (ATC Part 10, interlock and E-stop wiring) similar to what you want and he explains it well, worth a watch it's only 30mins

[Muzzer]

The supplier has just got back to me and suggested increasing the Break Resistor to a 1500w 75ohm type, but from my understanding a 75ohm would take even longerr to stop than my 1000w 60ohm one..?

Haha yes, that wouldn't help. Did you lower the threshold voltage (parameter 01_31) to 600V (not critical but probably helps)? Brake utilisation rate (01_30) probably needs to be 100% for max effect. You might also need to set stop mode (01_07) to zero ie "decelerate stop" - it sounds as if you may have it set to 2 ie "DC braking".

One of the issues with Chinesium products is often the machine translated manuals causing issues like this. Ask me how I know!

[Phil Mayor]

Hi Muzzer,

Ok, so I've double-checked those settings and they are as above, I've also done more testing today... I'm beginning to wonder if the Braking Resistor terminals are even connected on the PCB Board - I tested the following

1) No Break Resistor attached to VFD, DC Brake off (01_07 - 0)
2) No Brake Resistor attached to VFD, DC Brake on (01_07 - 2)
3) Brake Resistor attached to VFD, DC off (01_07 - 0)
4) Brake Resistor attached to VFD, DC on (01_07 - 2)

1st test had a fault and the Spindle just free-wheeled to a stop after approx 2min 30seconds
2nd test stopped on 21 seconds +/- .5
3rd test stopped on 21 seconds +/- .5
4th test stopped on 21 seconds +/- .5

The internal built-in brake is slowing it down but isn't powerful enough to stop it quickly and for whatever reason the external Brake Resistor is having no effect I have checked the Break Resistor for resistance with my Multimeter and it's saying 60ohms so I can only assume it's ok... I would like to know is there a way to check the actual VFD with my Multimeter to see if the DC Brake wiring is even connected... I don't know where I would need to put the multimeter prongs to test or what setting to have it on, if you or anyone else knows that would be great.

Cheers,


Phil

[Muzzer]

If you trust yourself, you could put your voltmeter across the braking resistor and see if any voltage appears across it during decel.

As you say, some VFDs ship without the braking resistor circuit fitted.

What decel time is programmed?

[Phil Mayor]

I set the Decel time to 3.5s

Yeah I'll have a go... so, just to be clear,

Do I set Voltmeter to DC... I know it goes in as AC but then it gets converted at some point to DC, then back again to AC, is that right..?
and just put the Red on the DC+ or R+ Terminal that the Brake Resistor is attached to and the Black to the R- Terminal that the Brake Resistor is attached too?
and take the reading as I hit stop

[marky68]

Following you guys on here and this thread too, https://www.mycncuk.com/threads/13405-chinese-atc-spindle . :link:

I've just started my conversion, mines a similiar spec to voyager1972. 6Kw HQD Atc spindle, ETH300 with UBB board & Uccnc controller...

Pity we're not all located close to each other..

[voyager1972]

marky68 my biggest fear was that i would make a bollocks of it ,once i got started my confidence came back and everything went ok , the only thing i need to sort now is the touchprobe as those spindle have ceramic bearings , im not sure how to get around it yet

[marky68]

marky68 my biggest fear was that i would make a bollocks of it ,once i got started my confidence came back and everything went ok , the only thing i need to sort now is the touchprobe as those spindle have ceramic bearings , im not sure how to get around it yet

I know the feeling, I'm treading slowly with it.. a lot of research done so far. It seems a bit of a black art probably as every machine is different.

[marky68]

I set the Decel time to 3.5s

Yeah I'll have a go... so, just to be clear,

Do I set Voltmeter to DC... I know it goes in as AC but then it gets converted at some point to DC, then back again to AC, is that right..?
and just put the Red on the DC+ or R+ Terminal that the Brake Resistor is attached to and the Black to the R- Terminal that the Brake Resistor is attached too?
and take the reading as I hit stop



Not sure if this helps as it's a different VFD and spindle to yours but i did find out that if you don't get the parameters just right then there is no braking through the brake resistor.


32221

[Phil Mayor]

Hi Marky,

it might help, it certainly gives a better explanation of what the parameters do, I'll have a look when I'm home later, cheers for this

[Phil Mayor]

Had another message from the Supplier saying I should try a 1500w 75 ohms Brake Resistor to be sure mine isn't broken!

So I've quickly tested the Volts across the Breaking Terminals (R+ and R-) and had absolutely no Volts showing after pressing stop on the VFD. (see vid)

Is this enough to say to the Supplier that there isn't an external Brake Circuit on this VFD or are there more tests I can do to confirm 100%


https://youtube.com/shorts/Vk_4jPkJnHg

[Muzzer]

Well certainly there's no brake resistor action going on there. You can check the resistor is still intact with your DVM. Obvs no need to actually replace it to check that - but with no voltage, it's rather academic to begin with.

The other option is as marky68 says - some parameter somewhere that isn't right, preventing it from working. A VFD without a braking resistor is pretty useless TBH.

Have you definitely selected braking resistor rather than DC braking?

[Muzzer]

I have to admit I took the easy way out and coughed up for a Yaskawa GA5 (latest generation) last time round. These are £390 plus £80 for the dedicated EMC filter ie basically £470 all in. https://inverterdrive.com/group/AC-Inverter-Drives-230V/Yaskawa-CIPR-GA50CB018ABAA/. That might seem a bit extravagant but at least with these you know they will work and should be reliable. They are proper industrial parts with 150% overload (60 seconds) and will run at full power all day long (as if!!). The setup software is pretty slick too of course.

Most mfrs offer up to around 4kW maximum in 230V single phase, so above that the choice is rather limited. What power are you looking for here?

[Phil Mayor]

Hi Muzzer,

I thought I'd give the VFD another test as I was in quite a rush yesterday. Instead of having the prongs balancing on the (R+ and R-) terminals I placed them inside and screwed down on them to make sure of a good connection, and sure enough I did get a reading, it was around 7VDC at idle, 16vDC during acceleration and top speed, then went up to 22vDC during Braking - I tried this around 3 times with the same results...I then tried it between (DC+ and R-) with pretty much the same results.

I remember reading (Page 21) that (DC+ and DC-) terminals could be used also (not sure if this is my bad Understanding or the Chinglish) for an external brake (although I'm not convinced) so I decided to test those terminals and they're reading around 330vDC during acceleration and 370vDC on the brake - but I'm not sure I want to connect the Brake Resistor to these....?

I actually thought this VFD would be good as it had so many more parameters than my last small VFD and it was around £300, tbh it might be me, I kinda hope it is, and the penny drops and I realise there's something I've missed, but I feel like I've, checked, double checked and triple checked everythung...

[Muzzer]

Haha no, don't connect the resistor across DC+ and DC-. That is rectified mains voltage.

You misread / misremembered the words "Braking resistor is connected between R+ and R- or DC+ and R-"

The "R-" terminal is the braking resistor switch that goes low when the VFD wants to initiate braking. Otherwise it draws no current and should read 330V or so.

What is your decel time set to? If it is set nice and short, the decel should cause the voltage to rise until the braking threshold is met, at which point, voltage should appear across the resistor.

[Phil Mayor]

Hi Muzzer, my instinct was correct then, I haven't connected the Resistor to the DC+ and DC- so that's a good thing.

You say the R- should read 330v, so are those readings for the R+ and R- bad then the max it went to during Braking was 22vDC

I've had the Decel set on quite a few different settings during the test but I think it's 5 seconds at the moment, the quicker the better, so I could bring that down to 3 seconds maybe... I think I kept getting faults the last time I changed it too low, but 3 seconds might be ok...

[Phil Mayor]

I think I'm going to try to return this VFD, I do think it's quite a good bit of kit, it's just the Chinglish that makes this a much harder job, I've spent the last 2 weeks trying to figure this out and it feels like I take one step forward and 2 steps back.after all the testing I've done, I'm confident there is some fault somewhere.

Thanks for all the help so far, it's a shame I couldn't get it sorted but I do appreciate it

Phil