Special VFD from Mitsubishi

[mikey553]

I just bought a FR-D720S-042-NA Mitsubishi VFD from Ebay. It was sold as new and it looks and feels like new. However there are a couple of "Sample" labels attached to it and a "Special 4136" label at the front. It was manufactured in February 2017.

When powered, it does not look and perform like a regular VFD. Many parameters are missing, there are some extra ones, the default values are different from the manual. The base frequency parameter P3 does not exist and I cannot set the maximum frequency P1 above 206 Hz. The 1/3 HP motor, connected to the drive, runs, but the highest frequency on the display is 70 and the Hz LED is not lit. In reality the VFD max frequency going to the motor is about 40 Hz, I checked the motor RPM with a tachometer. There is nothing wrong with the motor, I checked it with another VFD. So I can run very low motor RPM with this VFD, but I cannot run fast.

How can it be? Is it the result of a special firmware? Why would somebody make a special VFD like that? I also noticed the same seller sold similar VFDs before and has one more for sale right now. They all carry a "Special" label, but each one has a different number. The seller claims to have no knowledge about this and offered me a full refund. I called the Mitsubishi technical support, but they do not know anything about it.

 

[jim rozen]

Some VFDs have a lockout parameter that prevents setting some parameters. Check in the manual, if no manual check in the higher regions of parameter space. In the Hitachis this is third level up.

 

[mikey553]

Some VFDs have a lockout parameter that prevents setting some parameters. Check in the manual, if no manual check in the higher regions of parameter space. In the Hitachis this is third level up.

I have checked the drive for lockouts, but it is not the case. I have a couple of Hitachi drives and I like their manuals much more that Mitsubishi. In this VFD it looks like somebody modified the parameter table and values to make it "special" and not much usable to me. Mitsubishi tech said only Japan has this capability.

 

[rons]

The labels might mean a profile of parameters that somebody saved.
Maybe. But a full reset of the drive parameters is the final word.

 

[mikey553]

The labels might mean a profile of parameters that somebody saved.
Maybe. But a full reset of the drive parameters is the final word.

I have done ALLC (all parameter clear), which resets the drive to as factory condition. It did nothing. I am still missing about 60 parameters and there are many new ones, which I don't know what they are. The parameter defaults after reset are different from the manual. That is why I think the firmware is special on this drive.

 

[mksj]

Manufactures sell VFDs setup to a companies specs, as such they have limited programming options and are not resetable to factory default specifications. This is not uncommon to see these selling as NOS, but they end up not being configurable.

 

[JST]

Yep. A bunch of the "forbidden brand" were sold for a while that had special spindle drive programming.

Just as in your case, there were missing parameters, and others that could not be reset.

At one point my employer ordered several large VFDs with special programming, for a particular client project. They were not like the standard ones at all.

There is probably nothing you can do to change the programming, so if you can get a refund, go get it.

 

[rons]

There is a thing called firmware upgrade. I would think a modern drive would do that easily today.

 

[mikey553]

There is a thing called firmware upgrade. I would think a modern drive would do that easily today.

And how would you do that?

 

[JST]

You have to beg the manufacturer for it. It might not be cheap, and almost certainly won't be free.

Hence the refund being a good plan.

 

[mikey553]

I have received a full refund and they let me keep the drive. However I have not given up on this drive yet. I cannot upgrade the firmware or replace the control board without a substantial charge from the manufacturer. So that is out of the question. But I have one application, where the slow frequency and no extra features are sufficient. All I need is a remote start switch.

I have never done a remote operation before, so I just followed the manual. It is a simple ON/OFF switch, which I wired between STF and SD control terminals. The control logic is in the sink mode like it came from the factory. Switching to EXT mode and turning the switch to ON produced very low speed of the test motor, about 35 times lower than operating from the control panel. I have tried it several times back and force between PU and EXT modes and it is consistent. Nothing else is connected to the control terminals.

Why is that happening? Which parameters do I need to check? I am new to Mitsubishi VFDs and other VFDs as well so please be patient with me. I would appreciate any help I can get from you.

 

[JST]

Remote usually also needs a remote potentiometer for speed control. Most will work with a pot between 2k and 5k resistance, wired from reference voltage to local common, with slider going to the speed input.

There are parameters to select remote vs local, and how the remote operates. The speed ref may be analog, via a current or voltage, high end of pot can be low speed or high speed, etc, etc.

If you have a manual, check that. It may be a bit dense and hard to read, but you need to get a handle on how to set it up. The manual may apply, but it is also possible that the unit as modified does not include all the options and parameters. It should be able to do the speed range however. If you have a manual for that version, you are golden, but........

 

[Jraef]

And how would you do that?

It usually means removing an EPROM chip and burning a new EPROM, which if you don't have an EPROM burner and the proper firmware to put back on it, is not something you can do. In some cases with small equipment like this, the EPROM may be surface mounted to the board, which would take a whole other level of skill to remove it and replace it.

 

[rons]

A average PC motherboard from 20 years ago could be re-flashed.
If a VFD has a communication port and flash memory then upgrades are no problem, physically.

 

[mikey553]

New generation of Mitsubishi VFDs has an online upgrade capability, But this drive, which is only 5 years old, does not have it. Mitsubishi tech said that replacing a control board may be the answer.

 

[JST]

It usually means removing an EPROM chip and burning a new EPROM, which if you don't have an EPROM burner and the proper firmware to put back on it, is not something you can do. In some cases with small equipment like this, the EPROM may be surface mounted to the board, which would take a whole other level of skill to remove it and replace it.

Eproms are very 20th century.... these days it is virtually all flashable memory on-board the processor.

The issue is if the board does not provide access to the programming lines. That's often the case, because the program in some if not all modern processors can use them for I/O. So the processor may be programmed in a fixture and then soldered-in.

Some bright folks program with a test program, and bootloader, so that the off-shore assembly house does not have code access. Then there is a way to get at some form of programming lines, because it is done over here after testing.