The following scenario explains how to set up a EMHEATER VSD with a Pressure Transmitter to provide Constant Water Pressure using an external analog signal (such as a PLC) to modify the target pressure (Variable Target Pressure).
For other similar scenarios please also see:
– To set up a EMHEATER VSD with a Pressure Transmitter to provide Constant Water Pressure using the VSD Parameters to set a Fixed Target Pressure, please see the relevant FAQ entry here.
– To set up a EMHEATER VSD with a Pressure Transmitter to provide Constant Water Pressure using an external Multi-Stage Switch to modify the target pressure (Target Pressure Selector), please see the relevant FAQ entry Here.
– To set up a EMHEATER VSD with a Pressure Transmitter for Frequency Control using a PID (Manage Water Outflow), please see the relevant FAQ entry Here.
– To set up a EMHEATER VSD with a Pressure Transmitter for Frequency Control using a PID (Manage Water Inflow), please see the relevant FAQ entry Here.
– To set up a EMHEATER VSD with AI Input Overrun Limit (using a Pressure Transmitter as STOP), please see the relevant FAQ entry Here.
For additional Protection Features, please also see:
– To set up a EMHEATER VSD End of Curve Parameters (PID Signal Loss Protection), please see the relevant FAQ entry Here.
– To set up a EMHEATER VSD Low Current Protection (Dry Run Protection), please see the relevant FAQ entry Here.
– To set up a EMHEATER VSD Restart (Delayed) after Low Current Protection Condition Occurred (Dry Run Protection Reset), please see the relevant FAQ entry Here.
SCENARIO
Use a Pressure Transmitter to measure water pressure in a pipe (use 4-20 mA Pressure Transmitter) and control the speed of the VSD based on a Target Pressure as set using a PLC input (use 4-20 mA PLC Input). If a 20 Bar Pressure Transmitter is used it will read 12 mA from the Pressure Transmitter if the water pressure in the pipe is 10 Bar – if the PLC sends a signal of 16 mA the target pressure is seen as 15 Bar and then the VSD speed will increase until the Pressure Transmitter feedback also equals 16 mA (and thus equals 15 Bar).
When the measured water pressure (Pressure Transmitter Feedback) reaches the target pressure (PLC Input), the VSD speed (Frequency) will slow down and keep slowing down until it stops (0 Hz) or until the pressure drops again. To set the VSD to stop (Sleep) before reaching a speed of Zero Hz, a Sleep and WakeUp Frequency can also be specified (Sleep/WakeUp feature can be activated or deactivated depending on requirements). If the VSD slows its speed down to the specified sleep Frequency, the VSD will immediately continue to slow down to a complete stop. Once the speed required to reach the target pressure is more than the WakeUp frequency, the VSD will automatically start again.
WIRING
- Pressure Transmitter Wiring
Connect to AI2 and +24V (Jumper default position is set for mA)
- PLC Input Wiring
Connect to AI1 and +24V (Set the Jumper to mA – default is for Volts)
- Connect COM and GND
PARAMETER SETTINGS
For the Pressure Transmitter (4-20 mA / 0-20 Bar) Feedback Set:
- C0-03 = 1 (PID Feedback Source – to use AI2 as Feedback Source)
- B0-03 = 8 (PID Control – This is set so the VSD uses the PID to Control the Frequency)
- B5-12 = 2 (Minimum Value of the Analog Input – Value of Minimum Transmitter output if the range is updated to correspond to a 0-10 value range)
- B5-14 = 10 (Maximum Value of the Analog Input – Value of Maximum Transmitter output if the range is updated to correspond to a 0-10 value range)
For the PLC Input (4-20 mA / 0-20 Bar) Set:
- C0-00 = 1 (AI1 – This is set so the VSD uses AI1 as Input from the PLC to determine the Target Pressure)
- B5-07 = 2 (Minimum Value of the Analog Input – Value of Minimum PLC output if the range is updated to correspond to a 0-10 value range)
- B5-09 = 10 (Maximum Value of the Analog Input – Value of Maximum PLC output if the range is updated to correspond to a 0-10 value range)
For the Sleep / WakeUp Function Set:
- C3-09 = 0 (If setting C0-00 = 1 and C3-09 = 1 then there is NO Sleep / WakeUp Function (Disabled)).
- B2-24 = Dormancy Frequency (Frequency used as Switch OFF frequency to go to Sleep)
- B2-25 = Dormant Delay Time (Time delay before VSD goes to Sleep when reaching b2-25 Frequency)
- B2-26 = WakeUp Frequency (Frequency used as Switch ON frequency to Start the VSD)
- B2-27 =WakeUp Delay Time (Time delay before VSD STARTS again when reaching b2-26 Frequency to reach the target pressure)
The following table illustrates how/when the Sleep/WakeUp function is Activated/Disabled:
