Thread: Multiturn Variable Resistor for a VFD Remote

Originally Posted by Oldneweng

Stuart

All the shield needs is a current flow. This can be changed of course, but I chose this one because it is the supply connection. It should have a current flowing whenever shielding is needed.

Dean

Totally unclear as to what you mean, but I'm going to guess that you are using the shield as an extra conductor ( for the +10V? ) I have to say that's a very bad idea... first you won't have any shielding, you might as well run unshielded cable.

The voltage control input is susceptable to electrical noise ( more or less ) depending on the length of the cable and the environment it runs through, keep control cables away from power cables. Noise on the control voltage input will cause erratic VFD operation.

Finally, there should NEVER be current flowing in a shield... most shields are only connected to ground at the supply end and left open cct at the other end, to eliminate current flowing in the shield.

Ray

Dean,
can you remind us again of what your motor specs are?
Thanks

Originally Posted by RayG

Totally unclear as to what you mean, but I'm going to guess that you are using the shield as an extra conductor ( for the +10V? ) I have to say that's a very bad idea... first you won't have any shielding, you might as well run unshielded cable.

The voltage control input is susceptable to electrical noise ( more or less ) depending on the length of the cable and the environment it runs through, keep control cables away from power cables. Noise on the control voltage input will cause erratic VFD operation.

Finally, there should NEVER be current flowing in a shield... most shields are only connected to ground at the supply end and left open cct at the other end, to eliminate current flowing in the shield.

Ray

Maybe I have this wrong too. My main experience regarding shield wires is in the audio field. All shields carry the negative or return signal. I assumed the shield wires are acting as a Faraday Cage. I was wrong about the shield wire connection. It is connected to the ACM(GND) terminal.


Bob

The motor is a 7.5 Hp Delta / YY.

I have to admit that I now have a problem with the wiring. I am trying to track down a circuit diagram of some sort in my computer and on the forum. I am getting "H00.00" on the display. I wrote down all of the connections I needed to change, but a couple of others disconnected in the process. The old retighten after a while issue I think. I decided to replace all the wiring to the control switches with some new shielded I bought for this purpose. I soldered everything up or fitted boot lace terminals, to everything in sight. It now is much neater. The problem tho, is that there were some connections I did not record. I need to work out what I have done.

Dean

Originally Posted by Stustoys

.............................
If you think paying $400 more is going to get you a better manual..... I'd say you're going to be disappointed. Certainly there are a few less typos, but I find the Teco manual just as hard to nut out as that Haung. (in fairness I dont think these manuals were ever meant to be "A Noobies Guide To VSDs", like a lot of machine manuals they assume a certainly level of knowledge and leave you to it)
............................

Firstly, you do not need to "pay $400 more". Most of my VFD's were bought NOS at MUCH less than half new price.

Second, I can assure you that VFD's like Yaskawa, Omron, Siemens, Telemecanique, Hitachi, Lenze etc etc come with very exhaustive user manuals, with well written examples and explanations for each and ever software setting. They all also come with shortform quick guides (the shortform "quick start guide" for my Yaskawa V7 is alone 34 pages, the user guide another 260 pages....). Additionally you can download installation manuals and often also several application notes. Nowdays many VFD's do come with a DVD containing all relevant manuals as .pfd files.

Before buying a VFD, I highly recommend to download user guide, quick start guide and the installation manual from the makers website. If these manuals are not available as a free download or do not contain exhaustive information, I will not buy that VFD no matter how cheap! Because I do not want to spend hours and maybe days trying to reconstruct how its intended to work or how to access certain functions.

Another reason to download at least the user manual, is to decide if one likes the way the particular VFD is programmed. Some are very easy to mavigate the menues and change parameters, some are not and best avoided.

Originally Posted by Oldneweng

Maybe I have this wrong too. My main experience regarding shield wires is in the audio field. All shields carry the negative or return signal. I assumed the shield wires are acting as a Faraday Cage. I was wrong about the shield wire connection. It is connected to the ACM(GND) terminal.

Bob

Hi Guys,
In general a shield round one or more cables is always connected to ground. In audio, RF and other signal service the shield is only connected to ground at one end. The reason for this is that it prevents feedback loops between two or more disparate pieces of equipment. It is perfectly acceptable to use the shield to carry ground return currents where the remote equipment is powered by a conductor inside or outside the shield. Any interference or radiated stray signals will be kept on the outside of a shielded cable. However this will not prevent crosstalk between conductors inside the shield. It may be that Bob's pot would be perfectly OK using a shielded pair but it would be prudent to use shielded three core, this would at least remove any danger of having a voltage difference between two pieces of equipment or even worse taking a dangerous voltage level outside the VSD. There are other issues as well not discussed here but may affect the use of an external control.

I guess you'll know before I do lol. The Teco does, as do my "other" vsds, but I'm not sure what the Haung does.

No it doesn't. Changing this parameter to the minimum value only made it update faster.

How you going to supply a 7.5kW 240V VSD?
Is this the motor that is still wired for 415V? You removed the pole switching if I remember correctly?(I'm pretty sure we have been down this road before)

Yes we have been here before, and the concensus was, if I remember correctly that I need a bigger VFD. I don't need to supply a VFD to 7.5kw. I just want to get better than I have now which is a maximum of about 12A before it decides to stop. It was supposed to be rated at 23A. I will be happy if I can run it at 100Hz, which gives the normal maximum spindle speed.

Yes I removed the pole switching. The motor is currently wired for Delta. I get full speed from it in this configuration. 50Hz equals 1000rpm, just like it is meant to.

What I know about shielding can be covered in about two sentences and even then half of it is likely to be wrong. But if the shield is in the circuit... don't you just have an aerial? I thought only one end of the shielding should be grounded?(not talking about twisted pair here. not that I have paid much attention to it as I've not had any issues as yet)

I asked the electrician about this at work today. He said that there are people who use both methods and even some VFD manufacturers say to use the shield to run the return (GND). They only earth the shield at one end themselves.

Note that it is the ACM (GND) that the shield is carrying, not the 10v as I said previously.

Hi Guys,
In general a shield round one or more cables is always connected to ground. In audio, RF and other signal service the shield is only connected to ground at one end. The reason for this is that it prevents feedback loops between two or more disparate pieces of equipment. It is perfectly acceptable to use the shield to carry ground return currents where the remote equipment is powered by a conductor inside or outside the shield. Any interference or radiated stray signals will be kept on the outside of a shielded cable. However this will not prevent crosstalk between conductors inside the shield. It may be that Bob's pot would be perfectly OK using a shielded pair but it would be prudent to use shielded three core, this would at least remove any danger of having a voltage difference between two pieces of equipment or even worse taking a dangerous voltage level outside the VSD. There are other issues as well not discussed here but may affect the use of an external control.

Best Regards:
BaronJ.

It seems I am already running ground return currents as you mentioned.

When you mention dangerous voltage levels are you refering to the risk of a fault sending high voltage thru the external control wiring?

Anyway the latest update is I suspect a problem with the VFD. Tonight I reconfigured it to run from the digital controls of the VFD. It ran perfectly. I have rewired all the controls with better colour coding and tidied it up. Configured back to external controls again and it appeared to be working, but nothing happened. The LED readout was showing all the right information, I could hear clicks inside when I pressed FOR or REV, but the motor would not turn. I checked all pot connections and the pot resistance. All as expected. I am not sure what to do next.

Dean

Originally Posted by Oldneweng

.
.
.
Yes we have been here before, and the concensus was, if I remember correctly that I need a bigger VFD. I don't need to supply a VFD to 7.5kw. I just want to get better than I have now which is a maximum of about 12A before it decides to stop. It was supposed to be rated at 23A. I will be happy if I can run it at 100Hz, which gives the normal maximum spindle speed.

Yes I removed the pole switching. The motor is currently wired for Delta. I get full speed from it in this configuration. 50Hz equals 1000rpm, just like it is meant to.

12A??? that sounds like like a 4HP not 4kW VFD.
I've heard of these getting mixed up
A 4kW HY will get you to about 18A before it drops out,

There's a significant difference between the 4HP and 4kW Hys
The 4HP is the same physical size as the 3 and 2HP unit whereas the 4kW is bigger i.e. the one on the left,



BTW If you want the full performance from the motor using a HY, not only does it have to be ∆ it has to be 240∆, if its a 415∆ it will still only give about half power.

Have you tried running the motor completely unloaded?

Originally Posted by Oldneweng

..................................snip................

Anyway the latest update is I suspect a problem with the VFD. Tonight I reconfigured it to run from the digital controls of the VFD. It ran perfectly. I have rewired all the controls with better colour coding and tidied it up. Configured back to external controls again and it appeared to be working, but nothing happened. The LED readout was showing all the right information, I could hear clicks inside when I pressed FOR or REV, but the motor would not turn. I checked all pot connections and the pot resistance. All as expected. I am not sure what to do next.

Dean
[/INDENT]

Dean, just an idea. What sort of switches are you using for your external controls? You see, sometimes people decide to use the original forward-stop-reverse control gear, because its already there and in the right place. If contacts of these switches are in good condition that will likely work for a while. But if these have worn, burned or blackened oxydized Silver contacts from many years or decades of switching and breaking 420V to the motor, there may be a substantial contact resistance. The VFD control inputs work with only 10 or 12V DC, and very small currents in the order of milli-Amps. Such little currents are not sufficient to keep clean the contacts of high power 420V switches and contactors. This is why you should use switches that are designed for low DC voltages and low currents, usually with Gold plated contacts that do not oxydise and therefore will not require to carry high currents to self-clean.

Also, there may be several switches in series if you wired up things like safety switches for a chuck guard etc etc, adding more contact resistances together.

That's just an idea to look out for, your problem may be completely different altogether.

Bob it is a 4kW VFD. It is the bigger case size. No I haven't tried running the motor unloaded. It only gets up to 12A or so as I said and that is why I want a bigger one. If I can get it to do the full 2000rpm I will be pretty happy. I am not likely to put much load on it at this speed.

CBA the switches are 240 volt push buttons, but they were brand new when I put this together. The VFD is switching. The For and Rev led's change as they are meant to. Just no motor drive. The only external cause I can think of is the pot. Maybe the VFD is switching the motor on but there was not enough voltage from the pot to have the motor turn. I have checked the resistance of the pot including the leads, removed from the VFD. I think I will try the original pot back in it and see. At this stage the stop and brake switches are the only ones connected together and despite what people have said in the past they are N.O. so not in series. The fact that this is not ideal has been discussed as well. I am also going to go thru the VFD threads that I was using for my information way back then.

Dean

Originally Posted by cba_melbourne

Firstly, you do not need to "pay $400 more". Most of my VFD's were bought NOS at MUCH less than half new price.

And I'd argue you arent comparing apples.

Originally Posted by Oldneweng

No it doesn't. Changing this parameter to the minimum value only made it update faster.

Sorry didnt mean to imply that PD071 would change the display when the VSD is off. It just changes the rate the display follows the pot at when the VSD has output. Though I think there is a way to make the VSD display set freq when output it off........though it involes button pressing and not a default setting like you're after,. If I get time for a play tomorrow I'll have a look.

Originally Posted by Oldneweng

Yes we have been here before, and the concensus was, if I remember correctly that I need a bigger VFD. I don't need to supply a VFD to 7.5kw. I just want to get better than I have now which is a maximum of about 12A before it decides to stop. It was supposed to be rated at 23A. I will be happy if I can run it at 100Hz, which gives the normal maximum spindle speed.

Yes I removed the pole switching. The motor is currently wired for Delta. I get full speed from it in this configuration. 50Hz equals 1000rpm, just like it is meant to.

Ok I think I started this ball rolling. The original idea was to use a 240V VSD on your motor wired for 415V as you had a limited supply of 240V anyway. I think you're asking to much to try and run on half V at double Hz. Even if you get it to run you'll likely have little power. I guess there is about 0 chance you can put the pole switching back?

Originally Posted by Oldneweng

Anyway the latest update is I suspect a problem with the VFD. Tonight I reconfigured it to run from the digital controls of the VFD. It ran perfectly. I have rewired all the controls with better colour coding and tidied it up. Configured back to external controls again and it appeared to be working, but nothing happened. The LED readout was showing all the right information, I could hear clicks inside when I pressed FOR or REV, but the motor would not turn. I checked all pot connections and the pot resistance. All as expected. I am not sure what to do next.

We'd need picture and a list of your PD to have any hope of helping. Likely you'll see the problem tomorrow yourself. First thing I'd do is change it back to how it was last working. then change one thing at a time.

Originally Posted by cba_melbourne

Dean, just an idea. What sort of switches are you using for your external controls? You see, sometimes people decide to use the original forward-stop-reverse control gear, because its already there and in the right place. If contacts of these switches are in good condition that will likely work for a while. But if these have worn, burned or blackened oxydized Silver contacts from many years or decades of switching and breaking 420V to the motor, there may be a substantial contact resistance. The VFD control inputs work with only 10 or 12V DC, and very small currents in the order of milli-Amps. Such little currents are not sufficient to keep clean the contacts of high power 420V switches and contactors. This is why you should use switches that are designed for low DC voltages and low currents, usually with Gold plated contacts that do not oxydise and therefore will not require to carry high currents to self-clean.

Also, there may be several switches in series if you wired up things like safety switches for a chuck guard etc etc, adding more contact resistances together.

In theory yes but I've yet to have this problem. Most of my machines run the factory switch gear(except the shaper that uses second hand 240VAC contactors), still something to be aware of for sure. Might save someone some head scratching one day.

Stuart

Originally Posted by Oldneweng

Bob it is a 4kW VFD. It is the bigger case size. No I haven't tried running the motor unloaded. It only gets up to 12A or so as I said and that is why I want a bigger one. If I can get it to do the full 2000rpm I will be pretty happy. I am not likely to put much load on it at this speed.

Whats the error code?

Stuart

Originally Posted by Stustoys

Whats the error code?

Stuart

No error code is displayed. It just starts winding down. If you turn the pot back it will pick up again. I thought there was a fault at the time but someone on the forum said it was how they operate at overload. Hmm. Why have they got overload error codes then?

With the current situation I have scrolled thru the display and it shows no error codes either.

Dean

Originally Posted by Oldneweng

No error code is displayed. It just starts winding down. If you turn the pot back it will pick up again. I thought there was a fault at the time but someone on the forum said it was how they operate at overload. Hmm. Why have they got overload error codes then?

I'd say you've reached the limit of that motor(what do you have the motor current set to?). Not sure where you got that from...... as best I know the Haungs just shut down on overload(cant remember the code. after a certain amount of 150%), I'll be happy if I'm wrong though.

Originally Posted by Oldneweng

With the current situation I have scrolled thru the display and it shows no error codes either.

Yeah I doubt its a VSD issue, you've stuffed up the wiring or a parameter somewhere I think.

Stuart

Dean,

This can save you lots of time searching for your problem:

- remove all control input wires from the VFD
- select the factory defaults for all programmable parameters
- temporarily connect your basic single turn potentiometer to the speed controls
- use two peces of wire with stripped ends to manually connect the "drive enable" input and the "forward" or "reverse" input to the +12V of the drive. No worry, its only 12V, just do not accidentally touch the line voltage terminals....

If the drive correctly runs, your problem is with the control wiring. Follow carefully each wire. Use a beeper or an ohmmeter to make sure each switch does what it is suposed to do.

If the drive does not correctly run, you need to study its manual, its most probably a setup problem. You need to assign the proper function to each terminal before it does what you want.