Schematic of Robonic II Transfer Switch

Instruction Leaflet

30-471 (E)

Page 12

Schematic of Robonic II Transfer Switch

Consider the Robonic II in the normal operating position, with normal power available and the normal interrupter closed. The following are energized: U.V. (undervoltage module), TDES (time delay engine start), and NR (normal relay).

The U.V. monitoring all 3 phases of the normal power, senses a dip or loss of voltage which instantly causes NR to deenergize. Contacts NR2 and NR4 open, and contacts NR1 and NR3 close. TDES times out, closing it’s contacts and initiating the emergency system start up. When the emergency system reaches correct levels of voltage and frequency, ER is energized and contact ER2 closes. This completes the emergency control circuit, and TM (transfer motor) begins to operate.

First, the normal interrupter is opened, and then the emergency interrupter is closed. At this point, the ELS (emergency limit switch) contacts change state, and the BS (motor brake) closes, preventing TM over travel. The NLS (normal limit switch) contacts change state in preparation for re-transfer to the normal power source.

Upon return of stabilized normal power, NR is re-energized disabling the emergency control circuit, and enabling normal control circuit. The TM operates, opening the emergency interrupter and closing the normal interrupter. When the re-transfer is completed, the NLS contacts change state isolating TM, and BS closes. TDES becomes energized opening it’s contacts. TDEC times out to allow the emergency generator to run unloaded and cool off before shutting down. The Robonic II is now ready to react to another normal power failure.