Why is this drive not sutiable for this motor/application. 3

[bamia]

Hello,

I do not know the history of this job that I am now tasked with and the basic information I have is that "someone" installed the drive wired it up and then said it was not the right one.

This is a mixing application that is operating with the motor and gearbox in the pictures DOL with one problem, it is to fast; in certain situation and products. They may start fast and after the product is cooked/ready they slow it down. The products vary very liquid to much thicker and I hear they plan to mix some sort of tomato paste.

230VAC three phase power supply.
5.6 A Motor FLA
Drive output 7 Amps

Let's say the slowest the motor will run is at 30 Hz. ( I have to check motor specs for cooling requirements)
What would be other issues that I may be missing that would make this drive unsuitable?
I am still reading about its Vector Torque mode to find out what it does.

Thanks

 

[FacEngrPE]

There are other things to check besides the drive.

https://proquipinc.com/industrial-mixing-basics-mixing-impeller-power/

The power associated with an impeller is related to four primary factors:
[ul]
[li]Impeller geometry[/li]
[li]Impeller diameter[/li]
[li]Impeller rotational speed[/li]
[li]Fluid properties of the material being mixed[/li]
[/ul]

The mixer might need a different impeller.

 

[bamia]

Thanks FacEngrPE.

Doesn't the fact a motor and gear box have already be selected for the mixer and are working well mean that the torque produce by the motor and its current capacity is properly sized. Then the sizing of the drive is concerned with the motor current and torque requirement at the input of the gearbox?

 

[iop95]

Drive seem to be ok, have 7A output current.
Maybe acc time was set too low and drive go in overcurrent.

 

[Gr8blu]

bamia: Based on nameplate data motor is suitable for either 2 HP at slip speed (1750 rpm for 60 Hz supply, 1450 rpm for 50 Hz supply). Also capable of inverter operation for CONSTANT TORQUE RANGE of 4:1 ... which means at 30 Hz (on nominal 60 Hz) it will safely handle 1.0 HP load. Or 1.2 HP (on nominal 50 Hz). Motor current requirement is likely to go up slightly from the listed 5.6 A at 230 V but should not exceed the 7 A drive capability.

Check drive output waveform and harmonic content - and common mode voltage limit. Result may exceed motor insulation capability in terms of thermal (harmonics) or voltage (common mode offset).

Check drive switching frequency and grounding of both motor and drive. Impedance of ground path (if using cable) will climb noticeably with frequency to the point it may appear as an effective open circuit - which means damaged bearings and windings eventually.

What is the distribution voltage at the drive input? Should be 240/3 Vac. If lower may impact maximum amplitude of output voltage accordingly, where you're looking for 230/3 Vac.

Converting energy to motion for more than half a century

 

[FacEngrPE]

Doesn't the fact a motor and gear box have already be selected for the mixer and are working well mean that the torque produce by the motor and its current capacity is properly sized.

Your set of recipes range from vary very liquid to much thicker, so viscosity changes, thus shaft torque requirements change. Some of these may be thixotropic materials.
Just like any other VFD application, the motor and drive must be sized for the maximum shaft torque. If the shaft torque (drive output current) is too high, the impeller can be trimmed, the impeller pitch flattened, or the gearbox ratio changed to slow down the impeller. Lowering the drive speed will not help a shaft torque problem.

Recommendation fill your tank with thee product that is most viscous, (or perhaps a material with a slightly higher viscosity (thicker). If the current is equal to or less than nameplate at full speed, your components are correctly sized for this material.
If your current is above nameplate, you risk tripping on i[sup]2[/sup]t, the VFD version of motor overloads.
The best course of action is either of:
[ul]
[li]Establish a product viscosity limit for the process line[/li]
[li]Reduce shaft torque by trimming the impeller, flattening the impeller pitch, or adjusting gearbox ratio to slow down the impeller.[/li]
[/ul]

 

[bamia]

Thanks you FacEngrPE and Gr8blu.
The drive has been disconnected and the motor is wire DOL for the time being. The information I got was second hand and it will be a week or so before I get to connect it.
But, I had a look today and it has been wired, bot supply and feed to the motor, using 4/10 "cabtire"!

 

[jraef]

Huh... for some reason my replies are not going through if I make them from a phone.

..."someone" installed the drive wired it up and then said it was not the right one.

Was there a PROBLEM with it, or did they just SAY that?

That drive is not a great one and I'm not a fan (for mostly "historic" reasons) but capability wise, it should be fine. It is a notoriously "cheap" drive and sometimes people mistakenly believe that if it is cheap, it is rated for "variable torque" application (fans and pumps), because there are a LOT of cheap HVAC rated drives for that huge but price-sensitive market. But the reality is, most 2HP drives are not built as variable torque or constant torque rated, there is no economic reason to do so below about 10HP. So they are all constant torque rated. If they are just "saying" this, that might just be their assumption.

If the drive didn't actually function correctly, it might be related to an inexperienced person setting it up. Modern "Sensorless Vector Control" (SVC) drives like this one REQUIRE that the user perform an "auto-tune" procedure on any new motor it is connected to. Without that, the drive is going to use default settings that are almost always incorrect, resulting in the motor having poor or even erratic performance. When SVC first came out, most drives offered it as an OPTION, shipping the drive in what's called "V/Hz mode" (or sometimes "scalar" mode). V/Hz mode doesn't require an autotune, but it also doesn't perform as well, especially at low speeds. But eventually that flipped and SVC is now almost always the factory default setting, meaning you MUST perform that autotune. That's the first thing I would suggest checking and even if they said they did it, do it again, following the instructions VERY carefully. That's the #1 cause of people thinking a VFD is "not the right one".



" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[bamia]

Thank you jraef.

They just said that and by "they" I refer to management not technical people. I have not powered it up or done anything with it thus far. Whomever attempted this task ended up telling them that they probably need a "bigger one, like the one on the other machine" which is an 18 Amp output, 5KW and is properly sized for its motor.

I will follow your suggestion when I get to it next week.

 

[jraef]

Using a larger drive does not increase the motor power capability. You have a 7A rated drive on a motor that has an FLC of 5.9A.

Ignore the SFA by the way. The motor mfr will tell you that when used on a BFD, all motors are 1.0 SF.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden