In some cases it might be necessary to manage multiple VSDs using a single Analog input – for example: Using a single pressure transmitter to manage the speed of multiple VSDs. For such a scenario the Pressure Transmitter (Analog Input) can be connected in a series connection as illustrated in the image below (Pressure Transmitter is connected to VSD 1 and VSD 2 is connected to VSD 1).
VSD Wiring required as follows:
- VSD 1: Connect the Transmitter to the required AI Input and +24V and also bridge COM and GND.
- VSD 2: Connect the the required AI Input and GND to VSD 1’s AO1 and GND.
VSD Parameters to be set as follows:
- VSD 1: If using AO1 set b6-01 (or b6-02 if using AO2) equal to 7 (if AI1 was used for Transmitter Input, otherwise equal to 8 for AI2 or equal to 9 for AI3).
- VSD 2: Update the necessary AI (AI1, AI2 or AI3) parameters to ensure it corresponds to the 0 -10V output of VSD 1’s AO Output. Also ensure VSD 2’s AI input’s jumper is set for Voltage Input.
Please Note:
- 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.
- When using a metal transmitter connected to a metal piping system, please use a plastic connecter/fitting to isolate the transmitter from the metal piping system, or ideally use a plastic (PEX / PVC) pipe segment (20 – 30 cm long) to isolate the transmitter from the metal piping system. Also ensure the metal piping system is properly grounded (other electrical equipment and/or appliances could cause current/voltage on the metal piping system which will have an adverse effect on the transmitter output values).
- When using pressure transmitters, a buffer tube can also be added to prevent shock pressure transmission.
