Can we control the speed of a VFD by using an analog pressure transmitter, if so how can it be done
Run the VFD under by 4-20ma or either use the converter from current to voltage then make the VFD run by that setup…
Use vfd 0 to 10v or 4 to 20 ma.check this terminal parameters in vfd manual…set para 0v to 10v vfd function(inverse setting)…connect transmitter o/p 0 to 10v to drive …pressure increases…speed decrease,vice versa
Analog pressure transmitter is used to control the speed of a Variable Frequency Drive (VFD) since the method tended involves developing a closed-loop control system for the transmitter to feed back to the VFD.
Here’s a step-by-step guide on how to achieve this:
Step-1: Select the Pressure Transmitter
Step-2: Connect the Pressure Transmitter
Step-3: Configure the VFD Input
Step-4: Set Up the Control Parameters
Step-5: Define the Control Logic
Step-6: Tune the PID Controller (if applicable)
Step-7: Verify the Setup
Step-8: Fine-tune the System
Step-1: Select the Pressure Transmitter
It is vital that the pressure transmitter that you choose can interface with your system and provides an analog output signal in the common standard ranges of 4-20 mA or 0-10 V.
Step-2: Connect the Pressure Transmitter
Actually, wire the analog output of the pressure transmitter into the analog input terminals of the VFD. Check the manual of VFD for terminals or ask the electrical engineer for help on the right terminals.
Step-3: Configure the VFD Input
Go to the VFD’s setting function and configure the analog input according to pressure transmitter output range. For example, if the transmitter outputs is 4-20 mA, set the VFD to read this range.
Step-4: Set Up the Control Parameters
Set up the VFD so that the motor’s speed will be regulated according to the analog input signal. This typically involves setting parameters such as: Range of the input signal (Ex: 4-20 mA) minimum and maximum.
The motor speed range (for example, 0-60 Hz).
Step-5: Define the Control Logic
Select the control mode of the VFD to allow it to accept the analog output of the PLC as the speed reference. This may be achieved by choosing a PID (Proportional-Integral-Derivative) control mode if high level of control is required because of changes in pressure.
Step-6: Tune the PID Controller (if applicable)
If considering PID control, which is quite often in such applications, you will have to adapt the PID coefficients (proportional, integral and derivative values) to produce the right set-point response to pressure changes.
Step-7: Verify the Setup
Experiment and check the adjustment of the system where by one can change the pressure of the system and see the effect that this will have on the speed of the motor. Make sure the VFD arouses appropriately to the analog signal originating from the pressure transmitter.
Step-8: Fine-tune the System
It’s necessary to fine tune any of the parameters based on the performance that is to be obtained. This might refer to the input signal scaling, speed factors, or and/or fine-tuning of the PID constants.
Example
Basic Configuration Steps on a Generic VFD
Connect the Analog Signal
- Connect the 4-20 mA output from the pressure transmitter to VFD’s analog input terminal points.
Configure the Analog Input
- Program the mode of the analog input in the VFD to be in the range of 4-20 mA.
- Define the input signal of the analog (Ex: 4 mA = 0Hz, 20 mA = 60 Hz).
Set Control Source
- Set the VFD to have the analog input as a speed reference.
Enable PID Control (if needed)
- Make certain that the PID control is allowed in the VFD settings.
- Enter the set point into the PID for the pressure you want the system to operate at.
- The next parameter to adjust is the PID gains where one has to fine tune the values in order to get a stable control of the process.
These are the steps to apply if one wants to use analog pressure transmitter to control the speed of a VFD in order to have controlled motor speed that has a corresponding pressure.
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