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09-02-2012 05:26 AM

Variable frequency drive PID control

hello everyone,

Adjusting speed base on PLC and variable frequency drive closed-loop control, what we should concern to see the debug status of the equipments and parameters when we adjust the PID parameter?
09-02-2012 05:47 AM
Top #2
09-02-2012 05:47 AM
General speaking, the whole control system has three performance indicators: accuracy, stability and fast. We adjust the PID parameters of the variable frequency drive to make those three performance indicators as perfect as possible(those three indicators are constrained to each other).

PID parameter adjustment is a complex process, hence, the variable frequency drive manufacturers in order to simplify this work, they set some intuitive parameters as default, users only need to modify these parameters for debugging conveniently. Take an example of the accelerate time, you only need to adjust the accelerate time for the motor start, but you don't need to know the PID value after you set it. Another important parameter is the decelerate time, in some applications it needs fast stop time but it's not related with PID. In the debugging process, you can read rotate feedback signal from PLC to verify accuracy and stability, also you can see the time from stop to steady during the electric motor stop process to determine fast brake whether meet the requirements; In addition, you can observe the curve from software after you drag the feedback in it, it's more intuitive.
09-02-2012 05:58 AM
Top #3
09-02-2012 05:58 AM
Actually PID is a close loop control system, generally it's used in constant pressure water supply system, the variable frequency AC drive gets pressure signal from the output pipe, and then take a calculation to control motor speed in a certain range to stabilize the output pressure in a certain rang.

Years ago, AC drives are all basic control mode, rarely have PID regulator function, so in constant pressure water supply system it must use PLC, the PLC is to make the PID algorithm and logic control. Currently the variable frequency AC drive is developed rapidly, all are integrated PID control, even with few simple PLC functions, it's convenient for the application in constant pressure water supply.
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