Our project team is attempting to use a 7.5 kW 3-phase AC motor to run a brake dyno, and need a control method to run a set of predetermined speed sequences for testing purposes (ex. 30 rpm for 5 seconds, 50 rpm for 10 etc...).

It's still early days, but it's been clear that a variable frequency drive is the way to go to control the motor speed, so if we need to run some test sequences autonomously, what are our best options? From what we've found so far, VFDs seem suited to interfacing with programmable logic controllers. Are PLCs capable of running these tests if we have around 15 different test sequences the user can choose from? And I've also seen videos of projects where an arduino is used to output a PWM signal to the VFD to do the same speed control, but now with the bonus of being programmable, but the lack of documentation and "plug and play" potential is an acceptable yet disappointing compromise.

Forgive any apparent oversights, for we are mainly mech-fluids and mech-material students flailing around helplessly with these electronic components. Any wisdom and guidance would be appreciated and cheers in advance.

 

A VFD controlled by a PLC is the usual way to do this. Often using digital I/O signals to simply select pre-loaded speeds.

Many VFD's also have serial or ethernet ports and another way would be to write some simple software on a PC or laptop (in VB, Python, C, etc.) and interface this to the drive. This would be an inexpensive way to get a visual interface and more detailed control. Feedback to the PC - actual speed, current, etc. also possible.

 

Many VFD's also have serial or ethernet ports and another way would be to write some simple software on a PC or laptop (in VB, Python, C, etc.) and interface this to the drive.

This is pretty much perfect. We'll be needing a GUI anyway for other users to interact with the dyno. Is this connection with an RS-485 (no idea what it is, but it has been cropping up) and is accessing VFD I/O done with proprietary software?

 

Our project team is attempting to use a 7.5 kW 3-phase AC motor to run a brake dyno, and need a control method to run a set of predetermined speed sequences for testing purposes (ex. 30 rpm for 5 seconds, 50 rpm for 10 etc...).

Hello there
how many 7.5 kW 3-phase AC motor to run a brake dyno, are you allowed to destroy? I've seen it happen it's not pretty what I'm getting at is once you have the programming down and crossing your fingers before you apply power the power will be applied to three light bulbs one light bulb for each Polly phase. If anything untoward happens light bulbs are a expendable.

 

I agree with Marley, most VFD's have a RS485 port to operate under Modbus, you can send commands as well as read the various status registers.
Max.

 

I’m curious, only because I’m looking into dyno options. How do you apply an ac motor into a dyno application?