Using Mitsubishi A500 inverter with PCI-7344

[tommi_be]

Another question..

I am planning to use PCI-7344 to implement speed control for 7,5 kW induction motor. Mitsubishi A500 inverter driving the motor seems to have only speed (frequency) setting input. This axis don't have to make rapid movements, instead I'm looking for accurate speed and mostly rotation in one direction only. In the same machine there are servoaxises with Mitsubishi J2S servocontroller and they work OK. Movements of servos should be syncronized to the rotation speed of main axis.. I am asking this because it says in the manual that torque control should be used.

There are two pulse encoders in that 7,5kW axis. One in the motor and another in spindle axis after reduction gear. There is also orientation control/PLG feedback/pulse train unit (FR-A5AP) installed to the inverter. I'm not sure if that should be used or not.

Tommi

[Jochen]

Tommi,

it's a bit easier to tune a system that works in torque mode as typically you only have to tune the position PID loop of the board. That's why torque mode is recommended but that doesn't mean that you can't get good results with velocity drives, too. With a drive that works in velocity mode you will also have to tune the velocity PID loop of the drive and you will probably have to use Vff and Aff parameters of the PCI-7344 to reduce or eliminate the following error.

In order to get very accurate velocity and position control you should use both encoders of your 7.5 kW axis. The encoder that is attached directly to the motor should be configured as secondary feedback device, the other one as the primary feedback device. Please follow this link for further instructions. Also have a look at this tutorial, especially at the "Dual position feedback" paragraph.

Jochen Klier
National Instruments Germany