Setting up PID on an H100 VFD
PID (which stands for Proportional, Integral, and Derivative) control is a process control loop used to regulate a variable such as temperature or pressure. In terms of VFDs, this is usually accomplished with a transducer that provides feedback to the VFDs analog input. A set-point is setup in the VFD. The purpose of the PID loop it to automatically adjust and regulate motor speed to achieve a stable feedback as close to the set-point as possible.
PID example on an HVAC system
- Set PID01= Yes
Selecting and Scaling Units
- Set PID50 to the appropriate units. these units should match the transducer.
- Set the maximum transducer value in PID53. Example, a 150PSI transducer would be set to 150.
- Program the set-point (reference) source in PID10. Most applications use keypad.
- Input the desired set-point, the value you want to maintain, in PID11.
- Set the feedback source in PID20. This is most commonly I2 since transducers are usually 4-20mA
- Wire your transducer according to the below diagram. Watch for polarity!
The sleep function will put the drive to sleep (stop it) when system demand is low.
- Set the desired sleep frequency in AP1-08. This is the speed at which the VFD will go to sleep.
- A delay time for sleep can be set in AP1-07.
- In order for sleep to work properly a wake-up must be set. AP1-10 is a wake up deviation level. Example: If your set-point is 60PSI and the wake-up is set to 10PSI, the VFD will wake-up at 50PSI. 60-10=50.
- Additionally, there is a wake-up delay time set at AP1-09.
Submersible pumps often use a thrust bearing. The pump must ramp up to 30Hz within 1 second in order for the thrust bearing to be properly lubricated. Setup the below parameters on submersible pump applications.
- Set ADV60=30Hz. This is our accel/decel switch frequency.
- Set BAS70=1 second and BAS71=1 second. This makes the VFD ramp up to 30Hz in 1 second. It will also ramp down from 30 to 0Hz in 1 second.
PID Loop Tuning
If the PID loop is not responding quickly enough the below parameters are recommended.
- The default P-Gain in PID25 is 50%. It is recommended to set this at 100% for quicker response to feedback changes.
- PID26 is the integral time, and defaults to 10 seconds. Decrease this time to about 2 seconds to achieve a tighter PID loop.
The below settings will pin the set-point and feedback to the main monitor display. This will make it easier for tuning and monitoring the system responsiveness.
- Set CNF22=18 PID Ref
- Set CNF23=19 PID Fbk
LSE PID Guide (Cheat Sheet) for ALL LSE AC Drives
Quick view below or download the spreadsheet attachment.