Correct potentiometer for VFD

Don J

Don J

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My SouthBend Lathe came with a Huanyang HY01D523B VFD. My previous experience is with Teco's, but I got the manual and figured out how to wire up the remote potentiometer for speed control. So I hooked up the 10K pot, moved the jumper and got it working.

Except that the entire range of control for the frequency is covered by about 15% of the motion of the pot. I turned the pot to the point where I get the max frequency of the VFD and when I check the resistance of the pot, it's at 1.5K.

Would replacing the 10K pot with a 1.5K be the correct solution? Or am I missing something?
 
Disconnect the potentiometer and test to ensure you have the 10k ohm potentiometer.
Verify your wiring and try again.
 
Either it's wired incorrectly or you have a log taper pot (you want linear taper)
Not familiar with that VFD, the pot should connect to a internal + dc voltage (like 5 volts), a ground, and the wiper (center pin) should go to the control input-
3 wires total
If you monitor the wiper voltage with respect to ground it should go smoothly from zero to +5 volts across the full range of the pot
-Mark
 
How do you have PD070 set? The manual shows several options for reading the analog input, one is 10V, one is 5V, and there are a couple of current parameters which are used in industrial controls so not relevant. The wiring diagram and terminal input list is a bit inconsistent.

I'd try switching PD070 between 0 and 1 first. And as @markba633csi , make sure you have a linear taper pot which you can check with your ohmmeter.
 
Without even knowing the detail of the potentiometer control of the Huanyang HY01D523B VFD, I can share some of what I know about most all of these I have encountered. Most have an internal control way of altering the voltage, sometimes by pot, sometimes all digital, but for those which have a rotation pot, the external control ends up in effect simply wired in parallel. There is the reference voltage across the pot. It might be +5V. Some are 10V, some are between +5V and -5V.

The actual value of the reference voltage does not affect the proportional division of the pot wiper voltage. It can be anything the manufacturer designs in. The track of the pot is linear. It is not like the logarithmic variation as used for audio electronics volume control. The proportion of the the speed setting is a signal input speed demand to the VFD control.

The internal circuit might have have some ballast resistors either side of the control pot, to set the highest and lowest voltages the design might require, as well as safety limit the current in case of pot short or miss-connection. My first thought corresponds with yours, that is, to try a lower impedance (ie resistance) control pot. Say 5K, or 1.5K. Go carefully! On many systems, the external control has to be lower impedance that the internal control, so that it runs perhaps 5x or 10x the through current, to have enough authority to override the internal control.

The connections have to be correct!
The most common reason wired up controls deliver only partial control range is because one has wired the pot with the wiper swapped for one of the ends. This can be very bad, because at one end or the other, one could be short-circuiting the reference voltage. Good designs limit the current to the control.

Connecting these things up does not require much electronics knowledge, but one can make mistakes. There is no substitute for researching what is the correct control resistance. Very important is to get the connections right!

Your max speed arrives early
That you get the max speed when the control is only 15% of the rotation span, I think, is not totally fixed by changing the value of the pot to 1.5K, although the correct recipe is as you suggest. Strictly, you have to account for the 85% of the resistance that was still in there (as further to go), when you hit the maximum. Adding some ballast resistance to the higher voltage side of the pot allows more of the physical rotation span to represent the speed demand range.

This symptom still sounds like it could be wiper swap for one end miss-connection, but I am assuming you would get that right. :)
 
Pot is a linear taper and checks out as a 10K. Wired according to the manual.

I haven't checked PD070. I'll do that this afternoon.
 
A simple VFD pot debugging procedure​
If you are comfortable making measurements with the VFD powered up, I would suggest:

1) Measure from analog signal ground to positive voltage reference (+5/+10v). This voltage should not change significantly (more than 0.1 volts) as you turn the pot. Note that signal ground is a pot connection terminal, not the power ground terminal associated with the power to/from the VFD.
2) Measure the voltage from signal ground to the analog voltage input on the VFD (often called the AVI terminal) as you turn the pot. The voltage should vary from 0 to whatever you measured in #1, (to within less than a tenth of a volt).

The VFD has to be powered up, but you usually shouldn't need to have the motor running to make these measurements.

If these check out, then your pot is behaving correctly (regardless of pot value). If not, then your pot is not working right, whether wiring, linear/log taper, etc.

If these do check out, then in addition to the P070 voltage reference, there are several parameters in the VFD that effect speed range mapping, including offsets, etc. These are usually defaulted to values that should give you full speed range over the full pot turns, but if they are set oddly that can cause weird behavior.

The electrical theory here is that the pot is acting as a voltage divider. In a theoretical ideal circuit, the pot value does not matter as long as it is more than zero. In reality, too small of a pot (less total resistance) will draw more current than the voltage reference is capable of providing. Usually these things can provide in the ballpark of 10mA. Maybe as little as 5mA. As long as measurement #1 matches the VFD spec, then you are not drawing enough current to cause speed problems, ( although you could be drawing more than is good for the VFD's voltage reference circuit). If the pot value is too large, than the problem may be that the input impedance in the AVI terminal is comparatively too small. This means that input voltage can't reach full value, which would show up as not being able to get full range in measurement #2. In general pots between 2k-10k are reasonable values.
 
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PD070 was set to 1.

I set it to 0 and get similar behavior. Getting a little more sweep out of the pot. But not a bunch more.

I'm now suspicious of the other settings. I think that I'm going to reset the VFD to factory defaults and retry.
 
Signal ground to VR+ is 10.05v
Signal ground to VI runs from 0 to 10.05v. At a half turn on the pot the voltage is 5.0v. When I watch the display while turning the pot, it hits max frequency when the voltage is at 2.3v.

I'm going to see if I can figure out what other parameter is incorrectly set before doing a reset on the VFD.
 
More data. I switched back to the pot built into the VFD and that one only uses about 50% of its range (it hits max frequency after about half a turn).

I ran through the configuration and most of the settings were at the default. The ones that weren't looked correct except for PD072. In one part of the manual I have it shows that as "Lower Analog Frequency". Another part of the manual shows that as "Higher Analog Frequency". Both with a valid range of 0-400 and a default of 50. Mine is set to 400. I don't know what this setting does, but I think that I'll set it to 50 and see what happens.
 
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