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  1. #31
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    These devices use a solid state relay and when they say that is the max current they mean it!

    These devices will self destruct if over loaded. I wouldn't run them on any motor which may have a higher starting current. In fact they even show a circuit for the use of a contactor when connected to a motor.

    With a contactor they look like a real cheap option for a remote control.

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  3. #32
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    Quote Originally Posted by BobL View Post

    Thanks for the info on this. Is it being used on the control side or the power supply side of the VFD?

    Some have a fine print line in the description that says the 30A is "peak current" and if you look closely at the power rating they are rated at 3000W (or 12.5A @240V) and even then I wonder what the safety margin is.

    If it is being used on the power supply side, on a 3HP VFD with a soft start it should be Ok at 50Hz but I wonder what the current would be at 60Hz.

    At first glance these 50A rated ones would seem safer for non-VFD users if they wanted to switch a 2 - 3HP DC remotely.
    However reading on it also says - maximum continuous power rating is 3000W????

    On the subject of 50 - 60Hz, what would be useful is a device that could sense sawdust in a system and automatically increase the VFD frequency when needed. A standard dust detector/sensor would be too sensitive but some sort of optical sensor might work.
    I used the same remote on the power side of the 2HP DC for a year or so without any problems but, for the 3HP DC, we connected it on the control side to remove any issues with 'one on, one off' ....... and because I didn't have any piggy back plugs?
    The highest in-rush current we observed was only 5.3A although that was on 50Hz and so I have been able to plug the 3HP DC into a 10A GPO.
    In terms of the benefits the VFD has provided TO ME they seem now to rank in importance/value as;
    1 Allowing the use of a 3phase device on a single phase circuit
    2 Soft start, permitting connection to a 10A circuit
    3 Cheaper than a replacement single phase motor
    4 Operating features (especially speed change)

    Re the operational use of speed change, I hadn't considered any automated protocols but I was thinking of running the DC on 60Hz at the end of each day and cycle through all of the gates/lines for a minute or so on each?
    As suggested by NCA, I might also use some of the increased capacity to permit keeping a far gate slightly open to act as a sweeper during normal operation but I will have to check this because (at least) one of my 100 mm gated pipes howls like a pipe organ when open

    fletty
    a rock is an obsolete tool ......... until you don’t have a hammer!

  4. #33
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    Fair enough to use that switch on a the VFD control side if you already have it.

    Quote Originally Posted by fletty View Post
    Re the operational use of speed change, I hadn't considered any automated protocols but I was thinking of running the DC on 60Hz at the end of each day and cycle through all of the gates/lines for a minute or so on each?
    Venting at any time is a good idea but (especially if noise is an issue) there's usually little significant benefit in using increased speed for timed ventilation. 60Hz operation is only 20% more air flow and that can be achieved with the same effectiveness by just running the DC at the much quieter speed of 50Hz for just 20% longer in time than usual i.e. 1 minute and 12 seconds at 50Hz will pull the same air as 1 minute at 50 Hz.

    The most useful time to have extra flow is while the dust is being made, and second most useful time is immediately after the dust has been made.

    At these times every little bit of fine dust that escapes collection pervades the shed and exposes the operator. Most of that dust will probably have settled out by the time you come to vent the shed at the end of the say, and venting the shed won't pick up fine dust from surfaces anyway.

    The finest hazardous dust has a half residence time of about 25 minutes, that means half of this dust will fall out of suspension in 25 minutes. Hence the idea of sweeper operating during dust making sounds like a better approach although its better still if the sweeper was at the point of the dust making activity, and runs for some time just after the dust making operation.

  5. #34
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    The last two installations I have been involved with have been controlled by a garage door opener which cost less than ten dollars, both installed by NCA utilising Powtran VFD's controlling Clearvues.
    CHRIS

  6. #35
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    Just so nobody loses any sleep, the remote control unit is switching a miniature relay. the contacts of the relay are connected to a digital input of the VFD which is programmed for 2 wire control. Push remote button, relay operates, contacts close, VFD starts. Push button again, relay releases, contacts open, VFD goes into soft stop.
    For anyone else hooking up a VFD to a fan motor, I don't know if this is just Powtran or if it is a problem with other VFDs, the mechanics of a fan means that the VFD will get false feedback when the motor slows down prior to stopping. It will generate an error of overvoltage on the VFD. It's not a problem and just requires a second push of the stop button to clear the error. A second push of a remote button, however, will not work. The fix is to extend the deceleration time.
    The default decel time on the Powtran is 10 secs. If you push it out to 25 secs no error will be generated.
    Those were the droids I was looking for.
    https://autoblastgates.com.au

  7. #36
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    Quote Originally Posted by NCArcher View Post
    For anyone else hooking up a VFD to a fan motor, I don't know if this is just Powtran or if it is a problem with other VFDs, the mechanics of a fan means that the VFD will get false feedback when the motor slows down prior to stopping. It will generate an error of overvoltage on the VFD. It's not a problem and just requires a second push of the stop button to clear the error. A second push of a remote button, however, will not work. The fix is to extend the deceleration time. The default decel time on the Powtran is 10 secs. If you push it out to 25 secs no error will be generated.
    Good point about bringing up the deceleration/acceleration times.

    Over voltage errors (and possible eventual damage to the VFD) can result from decelerating loads with a high angular momentum (rotational inertia). The 1HP bench grinders I have running on VFDs are a good example. These generate an over voltage with even >30 s deceleration. However, the safest way to stop grinders is not to use any deceleration otherwise the grinding wheels may come loose. This is easiest set by a choice of deceleration or no deceleration (also known as a coasting stop) parameter.

    On my 150 mm belt sander with the 300mm sanding disc, a bit like a fan, I have to use a 25s deceleration time otherwise it generates an over voltage error.

    Some very cheap VFDs may not even have a coasting stop and a limited deceleration range. The $75 VFD that runs my 1/4HP squirrel cage ventilation fan has no coasting stop and a max deceleration time of 10s. Luckily this is a light weight fan (even though it pumps out 1200 CFM unrestricted flow) and 10 s is more than enough to cope without an over voltage error.

    The same issue of rapid deceleration applies to some extent to lathes, especially if large chucks and/or workpieces are used and if rapid deceleration is required. Some kind of chuck lock can be used to improve safety. On my 1HP Woodfast I have the deceleration set to 3 seconds which is fine for the mostly spindle work I do. With larger pieces one tends to run at slower speeds anyway so it is sort of self limiting. On the MW lathe which uses bigger chucks I also use 3 seconds and it seems to be OK. I do have a chuck lock for it which I can use if I need to.

    Acceleration times also need consideration - if a VFD or operator tries to accelerate a load too quickly it will also throw up an error. With the grinders and belt sander I have to set a slow than default manual speed change (via the external or built in pot) or the VFD will generate ad error.

    The other thing to consider is whether on not to employ the reverse direction.
    In a situation like a fan or a band saw it makes no sense and on the VFDs connected to these machines, reverse is removed as an operator option, like wise on grinders where a reverse is positively dangerous.

    On a DP I have found it quite useful. For example if a large bit jams on a DP, slow speed reverse can extricate the jammed bit. At slow speed, even under a vector drive VFD, the motor will have limited power so it will stall the motor well before it breaks a bit, about the only time the lower power at slow speeds is of any benefit. If you use sanding bobbins on a DP then a reverse might be useful. Also for those game enough to tap threads using a VFD powered DP the reverse is very handy. I have done this on thin Al and plastic and it it works quite well. I have used reverse on my belt sander because the rollers at each end of the bet are different sizes and sometimes one suits better than the other - the nuisance then comes regarding the need to reposition dust collection.

    Anyway I hope this provides folks with some ideas and gotchas to be aware of.

  8. #37
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    The error that occurs in the Powtran only came to light when the new P19 series went into service, whether they changed the timing or the software I don't know but it is a simple fix so really is not an issue. It also seems to be only confined to CV Maxes in my experience but I haven't seen a lot of installations with the new series and my own never gave the error controlling a CV1800 so I suspect the heavier impeller must have something to do with that.
    CHRIS

  9. #38
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    If you'd like to do some measurements Fletty, I'd be more that happy to ship my Hot wire anemometer down to you. It just needs a Smart phone or an iPad to run a program and act as it's display.

  10. #39
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    I have just received a reply from Powtran re the current displayed when the VFD is running.....

    If you didn't change any special parameter, the 1st monitor (the up bigger one) displays the running frequency (Hz), the 2nd monitor (the below smaller one) displays the combined running current (the actual output current)

    I can ask further questions if needed.


    CHRIS

  11. #40
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    Quote Originally Posted by Chris Parks View Post
    I have just received a reply from Powtran re the current displayed when the VFD is running.....
    If you didn't change any special parameter, the 1st monitor (the up bigger one) displays the running frequency (Hz), the 2nd monitor (the below smaller one) displays the combined running current (the actual output current)
    I can ask further questions if needed.
    Thanks Chris.

    I will need to measure the output V for VFD it's usually the same at 50 Hz and above but it may not be.

    @ 60Hz the Powtran shows 3.2A, but the input mains panel meter reads 1.2A and a Fluke Clamp meter on the input reads 1.65 A?
    @ 50Hz it show 4.4 A , panel shows 1.4 and the Fluke shows 1.9A
    @40 Hz it shows 4.4 A, panel shows 1.2 and Fluke shows 1.6A
    These are amongst the biggest differences I have seen between input and output currents.

    In the case of the panel meter I know it's not a true rms current sensor so I can understand if any non-50Hz or strange V waveforms will affect the reading and have seen this often on other VFDs.
    Even when the meter is on the input side there are significant V reflections back down the line that screw up the readings
    The Fluke meter is however a quality true RMS meter and is rated for a 40 to 400Hz frequency range, however it may not be able to handle weird wave froms.

    I will set up my breakout box on the output side of the VFD and measure the currents with the Fluke on the output side.

  12. #41
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    I measure the currents thru each phase fron the PowTran to a 3HP motor using the fluke clamp meter and while the readings are much closer than the currents seen on the input side they are still not the same.

    Freq (Hz); VFD display (A) ; Clamp meter reading for each phase (A);
    40 ; 4.37 ; 4.64, 4.68, 4.63
    50 ; 4.37 ; 4.69, 4.69, 4.63
    60 ; 3.28 ; 3.46 , 3.48, 3.50
    70 ; 2.72 ; 2.98 , 2.89, 2.98

    So it looks like the VFD display current might be for a single phase, if so multiply by 1.73 to get total current.

    Chris did you say a 3kW? motor on the Powtran displays ~9A when running the ClearVue at 50Hz?

  13. #42
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    Bob, are we talking input or output current, I think that should be stated to avoid confusion. I don't think I have ever taken readings at 50hz but if I did my memory is a blank. CMS state some figures for their Max on the website Corrimal Community Men's Shed Cyclone Dust Collection System - Automatic Cyclone DC System and we put a clamp meter on my 1800 when they were first looked at buying one and came up with a peak starting current of 16 amps INPUT for about one second then it settled down to about 7 INPUT (from a very shaky memory). I have been mucking around today with mine running it at different speeds and I can take some notes later. I wanted to see how 65hz worked and it appears by the seat of the pants flow meter to substantially increase the flow or at least enough to make it worthwhile to run it at 65hz. The noise level of the air flow is increased substantially over 60hz which makes me feel better!

    Edited for clarity, added INPUT
    CHRIS

  14. #43
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    Quote Originally Posted by Chris Parks View Post
    Bob, are we talking input or output current, I think that should be stated to avoid confusion.
    Sorry I should have been more explicit.
    Given its a single phase input and I've measured the currents for each phase that has to be output current i.e. current supplied by VFD to motor.

    I don't think I have ever taken readings at 50hz but if I did my memory is a blank. CMS state some figures for their Max on the website Corrimal Community Men's Shed Cyclone Dust Collection System - Automatic Cyclone DC System and we put a clamp meter on my 1800 when they were first looked at buying one and came up with a peak starting current of 16 amps for about one second then it settled down to about 7 (from a very shaky memory). I have been mucking around today with mine running it at different speeds and I can take some notes later. I wanted to see how 65hz worked and it appears by the seat of the pants flow meter to substantially increase the flow or at least enough to make it worthwhile to run it at 65hz. The noise level of the air flow is increased substantially over 60hz which makes me feel better!
    Thanks, thats good to hear about the 65Hz

  15. #44
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    I sent another email to Powtran and asked for a clarification on the displayed current as it is obviously not the total current being supplied to the motor or I didn't think it was and received this in reply....

    >It's not the 3 phase added figure, all the 3 phase are same figures (very small difference).
    One very important thing for VFD is that the voltage between phase to phase (U-W, U-V, V-W) must be in a balance (same figure or a very close figure).
    If the phase to phase voltage is not balanced, the VFD has problem<


    So in translation I take that to mean it is the output current for each phase to the motor. I have been dealing with the same person for many years so it is not some stranger replying to my questions and while his written english is very good sometimes it needs a bit of interpretation.
    CHRIS

  16. #45
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    Thanks Chris.
    Yes I am aware of the need for small differences between the phases. Some of the differences are meter interferences from the other active leads/fields and some are contact resistance differences. That reminds me that these contracts should be clean and form.

    I posted something on the effect of non-sinusoidal waveforms back in 2014 in this post VFD current waveforms and values
    And in this thread I compared the Fluke meter with the HY (True RMS current measurements) current display and another clamp meter
    The HY seems to show currents between 10 and 20% lower than the Fluke, while the Powtran is between 6 and 10% lower than the Fluke.

    I did a bit of reading and the the differences I'm seeing on the output side are almost certainly the differences in the current sensor characteristics and the algorithms used to determine the RMS current from a non-sinusoidal waveforms.
    Like all clamp meters the fluke clamp uses a coil to sense the meter - this has its own characteristic behaviour to waveforms so this has to be taken into account.

    In the case of the Powtran which is a quality product I reckon they would have used an algorithm(s) specific to their VFD output, while in the case of the HY we wont really know.

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