VFD Remote Control

I found a message recommending a "Type J" or RV4N potentiometer with a link to Jamerco for a remote speed control. The link came up with a 250K ohm pot. The manual for a VFD I have lists 1K ohm pot. Is there a general "ohm-age" for VFD's, or are they all different? I have another VFD without a manual so I am not sure what resistance is required to vary the frequency.

Does anyone make a remote pendant that can control on-off, forward, reverse, and variable speed? I've looked around a bit without finding much. I can put one together, but wondered if a better one is ma nufactured for use with VFD's

Every manufacturer has their own design as far as the pot ohms go. Some are 1K, some are 10k, a few are 250k. No way to know in advance without the data from the manufacturer. Many VFD manuals, even old ones, are available on the web.

For that reason, nobody makes a 'standard" pendant for controlling them. Even the buttons may be wired differently from brand to brand, so it's difficult to make a universal device. but there are pendant control stations out there which are configurable in the field, and some of them have a pot operator, to which you have to insert your own pot of the right value.

I've always thought some of these were cool, but might be expensive. I've never used them because I always build my own.

http://www.euchner-usa.com/pendant.asp

Not withstanding Jreaf's cogent advice, a Type J/RV4N pot is the best, and the one which should be selected.

How, and with what, one houses it is another matter entirely.

Bob Johnson said:

The manual for a VFD I have lists 1K ohm pot. Is there a general "ohm-age" for VFD's, or are they all different? I have another VFD without a manual so I am not sure what resistance is required to vary the frequency.

Does anyone make a remote pendant that can control on-off, forward, reverse, and variable speed? I've looked around a bit without finding much.

Click to expand...

I have found in general that the resistance has a fairly wide tolerance, the pot just sets up a variable voltage divider and due to the input via the slider usually being high impedance any value between 1k and 5k will most likely work, with 2.5k being a good middle-of-the-road value.
For making up a remote box, DigiKey has virtually all the components you need, Look at BUD for metal or plastic switch enclosures. Although the signals you are dealing with are low voltage, It is still good practice to take a ground to the remote unit.
M.

The speed pot necessarily goes to the analog side of the drive.

In every example I can think of, the bottom of the pot goes to the so-called "analog common" of the drive, which could also be called the "analog ground".

The top of the pot usually goes to a fixed voltage, often 10 volts, but it could be 5 or 12 volts.

The wiper of the pot goes to the (analog) "voltage command" input, also a part of the analog side of the drive.

As the pot is always acting as a potential divider, the minimum position, corresponding to zero volts into the "voltage command" input commands the drive to revolve at the minimum rpm set for the drive.

For the same reason, the maximum position, corresponding to 10 (or 5 or 12) volts into the "voltage command" input commands the drive to revolve at the maximum rpm set for the drive.

Any position in between obviously commands the drive to revolve at an intermediate rpm.

The value of the pot, therefore, is not THAT critical.

The value of the pot, therefore, is not THAT critical.

Click to expand...

Installed a bunch of them. Never even bother to check, as long as it's over 1k, and not cheap junk. (Hard to find less than 1k.)
It's a voltage divider circuit, normally from a current limited output. (You can't break it, really)
That being said there could be something I'm missing, but can agree with confidence, it's not that critical.
I'm pretty sure the inputs are looking at voltage and not current. Some one slap me around here if I'm wrong, since I should know better.

I would think about the cable you feed it with, it's length, and if it shares a raceway with line voltage. Those situations can be loads of fun.

Doug S.

Doug S. said:

I'm pretty sure the inputs are looking at voltage and not current. Some one slap me around here if I'm wrong, since I should know better.

Click to expand...

The main thing that would affect the value is that if the input impedance of the VFD was sufficiently low as to affect the resistance ratio of the divider, as most I suspect are relatively high compared to the divider, it will have very little effect.
The inputs often go into an op amp IC or similar, which unless this has a load impedance resistor, will not affect the divider.
The other thing to make sure of, is the pot is Linear type, not Logarithmic, otherwise you will have strange control effects, the log type is exponential in nature.
M.