14-11-2013, 09:18 AM
Hi,
Many thanks Refugee and Lawrence for your suggestions and information.
When I posted this thread I knew it was highly likely that no simple solution was available because of comments from members on other forums suffering the same problem.
If so many of us are having the same difficulty then why the heck can't Huanyang or their suppliers of these VFD's sort it out once and for all by simply replying to email requests for help which I've now asked for twice?
Over the last few days I've kept attacking this problem which I'm finding extremely frustrating to resolve; last night it once again kept me awake in bed and I've got up early this morning full of determination not to be beaten. I don't expect being led by the hand or for anyone to sort the problem out for me because this would exclude my input; I'm keen to learn and am very happy to be pointed in the right direction from all you knowledgeable members but I'm also happy to do a lot of research on my own because I want to understand the problem and the solution.
So far I've actually learnt quite a bit thanks to all your help. Refugee and Lawrence have opted for the voltage shunt method if I can use this term. By measurement using the DMM I determined the voltage range between stop and full speed which gave the base to work from and the value of the shunt resistor could then be calculated as 8K2.
For complete novices trying to follow this the 10VDC feed from the VFD to the speed control pot is too high so this needs reducing and the simply way is to use the fixed resistor (a second pot if accurate control is required). I'm still very much a novice to this kind of work but I can follow the resistor method easily enough and it does actually answer my question of how to get the pot to give full speed on full sweep; A simple highly workable solution to a deeply seated problem which to date still hasn't been fully resolved; the resistor method being a compromise.
I'm stubborn though and having gone to a great deal of time and trouble in restoring and upgrading this Graduate turning it into a superb lathe to own am I now going to be beaten by something so simple as a 10K Linear pot? Certainly not without trying everything at my disposal first and I still have other things to play around with; rather than get upset over this I'll now consider this problem to be just another project and spend time trying to sort it out so now rather than thinking ahead of painting the garage ceiling; installing lots of lighting; restoring the bandsaw and even doing a bit of woodturning I'm going to concentrate on this pot problem because I'm sure there must be a very simple solution?
Any manufacturer with the high levels of skill and expertise required to design and manufacture these VFD's would not state a 10K linear pot should be used if the pot did not work?
I've now reached the point due to your help where I could fully use the lathe without problem but knowing I had incorporated a compromise at this late stage would always trouble me especially if I simply accepted defeat. I'm obliged Refugee and Lawrence because you have given me a working solution and I now consider this to be "Plan B" if I'm unsuccessful in getting the VFD to work as intended by Huanyang?
In an earlier post I stated I could not understand the circuit diagram and symbols depicting the pot connections as shown in the supplied VFD manual. The oval dotted lines went straight over my head and as such I didn't know what these meant so excluded them working on the principle that ignorance is bliss? Nick kindly explained these dotted lines were the symbol of "Screening". I've heard of screening many times but never understood nor needed to understand it? I also stated that I spent ages just staring at the drawing thinking the drawing was trying to tell me something that I was completely missing?
All this now brings me back to you Nick; you stated clearly enough that screening of control leads is important? So far I've played around at length with assorted pot connections and adjusting parameters all not resolving the fundamental problem; last night it finally occurred to me to get involved with screening the cables even if this isn't the cause of the problem it will eliminate them?
The VFD is hooked up to the power supply by a standard 2.5mm twin and earth cable. The VFD to motor 3 phase is via a heavily screened cable but the screening at the moment is "floating" Lets take this cable first; connecting the screening at the pedestal is rather difficult because the cable enters the pedestal through a standard plastic gland; I believe only one end of the screen needs connecting? Would this be permissible to connect to the VFD metal enclosure which is earthed?
The un-screened signal cables are heavy duty 7 core trailer cable with only six cores being used these being three for the toggle switch and three for the pot. This cable leaves the VFD and travels through a brick load bearing wall all cables sharing a common hole being tightly squeezed together. The signal cable then connects to a large six way terminal block as used in electric motors which I had to hand; soldered eyelets terminate this cable to the block using nuts. From the block more soldered ring terminals are secured with nuts then taken to the toggle switch and pot controls these all being included within a metal enclosure. Also inside the enclosure are the stop/start relay and the relay PSU plugged into a standard 13A socket.
Thinking along Nick's lines all this lot must create one huge amount of "cross talk" and as the manual also shows screening have I completely missed the cause of the problem so easily by trying to take the simple route first?
Would this cross talk actually cause the pot to perform wrongly and if so what is the explanation; is it the cables piggy backing interference into the VFD control circuits? Please treat me like a raw novice because I simply do not understand screening and its implications.
In order to fully screen what do I need to do and what cable do I need to buy etc; I don't mind spending money to get this right. I'd like to add plug and socket connectors to both the toggle switch and pot cables if possible to make disconnection from the lathe easy should I need to move the lathe? What kind of plug/socket would be best for this application.
Sorry it's taken so long Nick to get around to this; I do take all suggestions and information offered most seriously but I'm unable to do everything at once and being human I try the easy options first or at least the options that I can understand; it might not even be the screening causing the problem but sorting out the screening once and for all will give the answer so I'm up for it and as I say I'm stubborn in the extreme.
Kind regards, Col.
Many thanks Refugee and Lawrence for your suggestions and information.
When I posted this thread I knew it was highly likely that no simple solution was available because of comments from members on other forums suffering the same problem.
If so many of us are having the same difficulty then why the heck can't Huanyang or their suppliers of these VFD's sort it out once and for all by simply replying to email requests for help which I've now asked for twice?
Over the last few days I've kept attacking this problem which I'm finding extremely frustrating to resolve; last night it once again kept me awake in bed and I've got up early this morning full of determination not to be beaten. I don't expect being led by the hand or for anyone to sort the problem out for me because this would exclude my input; I'm keen to learn and am very happy to be pointed in the right direction from all you knowledgeable members but I'm also happy to do a lot of research on my own because I want to understand the problem and the solution.
So far I've actually learnt quite a bit thanks to all your help. Refugee and Lawrence have opted for the voltage shunt method if I can use this term. By measurement using the DMM I determined the voltage range between stop and full speed which gave the base to work from and the value of the shunt resistor could then be calculated as 8K2.
For complete novices trying to follow this the 10VDC feed from the VFD to the speed control pot is too high so this needs reducing and the simply way is to use the fixed resistor (a second pot if accurate control is required). I'm still very much a novice to this kind of work but I can follow the resistor method easily enough and it does actually answer my question of how to get the pot to give full speed on full sweep; A simple highly workable solution to a deeply seated problem which to date still hasn't been fully resolved; the resistor method being a compromise.
I'm stubborn though and having gone to a great deal of time and trouble in restoring and upgrading this Graduate turning it into a superb lathe to own am I now going to be beaten by something so simple as a 10K Linear pot? Certainly not without trying everything at my disposal first and I still have other things to play around with; rather than get upset over this I'll now consider this problem to be just another project and spend time trying to sort it out so now rather than thinking ahead of painting the garage ceiling; installing lots of lighting; restoring the bandsaw and even doing a bit of woodturning I'm going to concentrate on this pot problem because I'm sure there must be a very simple solution?
Any manufacturer with the high levels of skill and expertise required to design and manufacture these VFD's would not state a 10K linear pot should be used if the pot did not work?
I've now reached the point due to your help where I could fully use the lathe without problem but knowing I had incorporated a compromise at this late stage would always trouble me especially if I simply accepted defeat. I'm obliged Refugee and Lawrence because you have given me a working solution and I now consider this to be "Plan B" if I'm unsuccessful in getting the VFD to work as intended by Huanyang?
In an earlier post I stated I could not understand the circuit diagram and symbols depicting the pot connections as shown in the supplied VFD manual. The oval dotted lines went straight over my head and as such I didn't know what these meant so excluded them working on the principle that ignorance is bliss? Nick kindly explained these dotted lines were the symbol of "Screening". I've heard of screening many times but never understood nor needed to understand it? I also stated that I spent ages just staring at the drawing thinking the drawing was trying to tell me something that I was completely missing?
All this now brings me back to you Nick; you stated clearly enough that screening of control leads is important? So far I've played around at length with assorted pot connections and adjusting parameters all not resolving the fundamental problem; last night it finally occurred to me to get involved with screening the cables even if this isn't the cause of the problem it will eliminate them?
The VFD is hooked up to the power supply by a standard 2.5mm twin and earth cable. The VFD to motor 3 phase is via a heavily screened cable but the screening at the moment is "floating" Lets take this cable first; connecting the screening at the pedestal is rather difficult because the cable enters the pedestal through a standard plastic gland; I believe only one end of the screen needs connecting? Would this be permissible to connect to the VFD metal enclosure which is earthed?
The un-screened signal cables are heavy duty 7 core trailer cable with only six cores being used these being three for the toggle switch and three for the pot. This cable leaves the VFD and travels through a brick load bearing wall all cables sharing a common hole being tightly squeezed together. The signal cable then connects to a large six way terminal block as used in electric motors which I had to hand; soldered eyelets terminate this cable to the block using nuts. From the block more soldered ring terminals are secured with nuts then taken to the toggle switch and pot controls these all being included within a metal enclosure. Also inside the enclosure are the stop/start relay and the relay PSU plugged into a standard 13A socket.
Thinking along Nick's lines all this lot must create one huge amount of "cross talk" and as the manual also shows screening have I completely missed the cause of the problem so easily by trying to take the simple route first?
Would this cross talk actually cause the pot to perform wrongly and if so what is the explanation; is it the cables piggy backing interference into the VFD control circuits? Please treat me like a raw novice because I simply do not understand screening and its implications.
In order to fully screen what do I need to do and what cable do I need to buy etc; I don't mind spending money to get this right. I'd like to add plug and socket connectors to both the toggle switch and pot cables if possible to make disconnection from the lathe easy should I need to move the lathe? What kind of plug/socket would be best for this application.
Sorry it's taken so long Nick to get around to this; I do take all suggestions and information offered most seriously but I'm unable to do everything at once and being human I try the easy options first or at least the options that I can understand; it might not even be the screening causing the problem but sorting out the screening once and for all will give the answer so I'm up for it and as I say I'm stubborn in the extreme.
Kind regards, Col.
Happiness is a wreck of a cabinet to restore.
