Drives Question – Programming

Hello,

I’ve been working on a drive project for our multi-conveyor system for educational purposes and have some questions regarding PLC programming for VFD/motor operation. On a practice setup I’m currently running a 1hp motor with a Siemens KTP600 HMI, S7-1500 and G120 CPU-240E-2 PN-F frequency drive (without a brake), although most of my questions are actually more general (and very basic) regarding drives programming with the PLC/HMI in general.

1) What manual controls would you generally use to control the drive from the HMI? In my current setup I’m using a speed input field (with set button), plus additional up and down arrow buttons to control the setpoint. I have direction, jog, run, stop and a fault acknowledge buttons. I’m wondering what controls one would commonly find out in an industrial setting.

2) What status values do you normally have displayed on the HMI in normal operation? I guess I’m wondering how you organize your HMI screens for motor control and how you structure you user authorizations for different data/controls.

3) I am currently using the basic ProfiDrive telegram with 2 word send/2 word receive communication. I send a control word and speed setpoint to the VFD, and receive an actual speed word and status word from the drive. I can extend the telegram to add things like current/voltage monitoring etc. What values do you find most useful and commonly transferred from the drive for use in a PLC program or display on an HMI?

4) Do you generally allow for VFD parameterization from the HMI, or just allow this to be done at the drive only?

5) Are there any programming techniques that are considered good practice when programming drives to cover the inevitable issues that arise if there is loss of communication between PLC/HMI and drive, motor/VFD overtemp, etc.? Any tips you can think of here would be great.

I’m sure I’m going to have a lot of other questions, so I’ll leave stick with those for now. Thanks for any input, really appreciate it.

I would strongly discourage any parameter changing from a communications link such as an HMI. Many parameters have direct impact on the safety design of the drive/motor system. These could be easily circumvented by accidently or deliberately changing the wrong parameter with disastrous results.

Thanks DickDV for the response. I know there are some people who like to make as much commisioning info available for changing in the HMI as possible. So you would not recommend this with VFD parameters, even where a top level user administration category is required? It seems like anyone with high level HMI access would be the same person who could access those same parameters in the drive itself. Giving the option to parameterize via HMI would be convenient where a lot of drives are used, but I guess once things are up and running there's rarely a reason to re-parameterize.

I would agree with DickDV. offering Parameterisation via the HMI is dangerous. The other thing that is potentially dangerous is directly starting or stopping a drive from the HMI as this may bypass a sequenced start warning system.

Other items that commonly get displayed as status might include: motor torque, fault code and motor temperature.

Other things that might get sent as setpoints are: Additional torque demand, torque limits and PID setpoints etc.

Nick

I would be more comfortable with HMI programming if, as you describe, there is no access to ordinary operators or maintenance personnel. When I see HMI access, I think operator access which would be unacceptable. The other follow-on posters have some very good points too.