Powerflex 525 has a frequency of 2-2.50Hz when being told to stop

[Tbone1465]

Hey all,

I am currently working on a depalletizer for a customer and we are doing a hoist upgrade. This is a SLC500 processor and the drives are being control through device net, besides the new powerflex 525 just installed yesterday. The Powerflex is being 2-wire controlled.

What is happening is when I run the hoist up, empty, it stops exactly when and how I want it to, I watched the faceplate and can see the frequency going to zero. Now when I run the hoist down I'm watching the frequency move between 2.0 and 2.5 Hz and the hoist drifts downward during this time until we get an F007 fault on the drive "Motor Overload".

My parameters are as followed:
P033 - 7.6
P034 - 7.6
P036 - 1768
P037 - 4.03
P041 - 2.0
P042 - 1.0
P043 - 0
P044 - 100
P045 - 0
P046 - 2
P047 - 7
P048 - 2
P049 - 7
P062 - 48
P063 - 49
P064 - 0
P065 - 7
P066 - 7
P067 - 13
P068 - 11
P411 - 12
P412 - 45
P442 - 2.0
P443 - 0.5

I will add that I am using a brake resistor and I have it set up in the parameters for dynamic braking.

Does anyone have any ideas what this might be or what is causing this, I have been working on this all day and cannot figure out why.

 

[Ken Roach]

PowerFlex 525's are compact and inexpensive but they are not a great choice for a hoist. They don't have torque proving or high-performance torque control and it's not standard to equip them with encoder feedback.

Do you have a physical shaft or rail brake on the motor or hoist ? Can you use Stop Mode 8 or 9 to control it ?

I realize you said you set up the dynamic braking resistor correctly, but please check Parameter A550, Bus Regulator Enable. By default it is on to prevent nuisance trips on deceleration, and it should be turned off when you're using a braking resistor.

Can you verify that the braking resistor is engaging ?

 

[Tbone1465]

PowerFlex 525's are compact and inexpensive but they are not a great choice for a hoist. They don't have torque proving or high-performance torque control and it's not standard to equip them with encoder feedback.

Do you have a physical shaft or rail brake on the motor or hoist ? Can you use Stop Mode 8 or 9 to control it ?

I realize you said you set up the dynamic braking resistor correctly, but please check Parameter A550, Bus Regulator Enable. By default it is on to prevent nuisance trips on deceleration, and it should be turned off when you're using a braking resistor.

Can you verify that the braking resistor is engaging ?

We have a physical shaft. How do I verify the brake resistor is engaging?

 

[kekrahulik]

Are you using an encoder and setting the drive up in flux vector control?

If you are trying to control a hoist with 525 in sensorless vector control, I expect you will have troubles at zero speed.

 

[Tbone1465]

Are you using an encoder and setting the drive up in flux vector control?

If you are trying to control a hoist with 525 in sensorless vector control, I expect you will have troubles at zero speed.

We are not using an encoder. But it's strange because the Powerflex40 is working and is what they have been using for years.

How do I set the drive up in Flux vector control?

 

[kekrahulik]

parameter 039. 1=sensorless (SVC) 3=vector.

You could try vector without an encoder, but that sort of pointless.

In sensorless, the drive needs to calculate motor position using voltage and current. Easily done while running - hard to do while still. Realize that to hold a load up, the drive must produce some frequency to provide an upward force to offset the downward load. If the drive put out 0 hertz, the load would fall.

I agree that a drive designed for hoists is the best approach. Encoder and vector the next best. Last option (which I don't agree with) would be to try autotuning or manually tuning the drive better than it is currently tuned.

If people can be anywhere in the line of fire, a drive meant for hoists is the right way to go.

 

[Tbone1465]

parameter 039. 1=sensorless (SVC) 3=vector.

You could try vector without an encoder, but that sort of pointless.

In sensorless, the drive needs to calculate motor position using voltage and current. Easily done while running - hard to do while still. Realize that to hold a load up, the drive must produce some frequency to provide an upward force to offset the downward load. If the drive put out 0 hertz, the load would fall.

I agree that a drive designed for hoists is the best approach. Encoder and vector the next best. Last option (which I don't agree with) would be to try autotuning or manually tuning the drive better than it is currently tuned.

If people can be anywhere in the line of fire, a drive meant for hoists is the right way to go.

Getting the right drive for that application is what I told the plant as well. This was just the drive they gave me to work with. I stopped messing with it, I put the Powerflex 40 back in and it is stopping exactly as it should. I'm confused haha.

But thank you all for your replying! It is much appreciated. I'm going to do some more research while watching production and see if I can find anything.