VSD Frequency Control using a PID (Manage Water Inflow)
VSD Frequency (motor speed – Hz) can be controlled using an external device (PID) such as a Pressure/Level Transmitter. For parameter settings, please consider the following example:
Example/Requirements as follows:
- PID: A 2-wire Pressure Transmitter is used requiring a 24VDC supply and with 0-10 Bar measurement range, providing a 4-20mA output (analog output).
- Connection: Connect the PID red cable to the VSD +24V terminal; Connect the green cable to the VSD AI2 terminal; Connect the VSD COM and GND terminals to each other. Please use shielded cable to prevent electromagnetic interference by other appliances on the analog signal sent to the VSD. For EMC Mitigation: 1) Allow for at least 20cm distance between communication cables and motor wires. 2) Do not use the same cable tray. 3) Insert wires in metal pipes if possible.
- Frequency Requirement: For this scenario the requirement is to fit a pressure transmitter at the bottom of a large dam/tank in order to measure how full/empty the dam/tank is. The requirement is then for the VSD to run a motor (pump) which fills the dam/tank at max speed when the dam/tank is empty (Pressure Transmitter will measure 0 Bar), and to gradually reduce the speed of the motor as the dam/tank fills up, with the slowest speed ~ 40Hz – at which point the dam/tank is close to full. When the dam/tank is full (Pressure Transmitter will measure 5 Bar) the VSD must switch off.
VSD Parameters to be set as follows:
- b0-02 = 1 (set Command Source selection = Terminal Control)
- b0-03 = 3 (Set Main Frequency Source to use AI2 – ensure jumper is set to “I”)
- b0-17 = 40 Hz (Set the Frequency Lower Limit)
- b2-17 = 1 (Set Running Mode to STOP when the set frequency is less than the Lower Limit frequency)
- b5-12 = 2 (Set AI2 Minimum Value) – (Setting range = 0 to 10 and transmitter range = 4 to 20mA, so 4mA in a range from 4-20mA corresponds to a value of 2 if the range is 0 to 10)
- b5-13 = 100 (Set corresponding value (Frequency) = 100% (50Hz) if AI2 = Minimum Value above)
- b5-14 = 6 (Set AI2 Maximum Value) – (Setting range = 0 to 10 and transmitter range = 4 to 20mA, so 12mA (at 5 Bar) in a range from 4-20mA corresponds to a value of 6 if the range is 0 to 10)
- b5-15 = 79.9 (Set corresponding value (Frequency) = 79.9% (39.95Hz) if AI2 = Maximum Value above)
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 analog signal (such as a PLC) to modify the target pressure (Variable 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 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.
