CONTROLS

Following one or more modes of controls are provided:

Manual Mode

a) Tap switch control method.
The DC output voltage of the TRU in this mode is controlled in 24 symmetrical steps by means of a separate autotransformer
with coarse & fine tapping. Autotransformer can have steps of 16, 24 or 64 as per customer specification.

b) Stepless autotransformer method.
The DC output voltage of the TRU in this mode is controlled by stepless separate autotransformer connected in primary of
main transformer.

Constant Voltage Constant Current Mode

In this mode the unit can be operated in either constant voltage or constant current mode. In constant voltage mode the DC output voltage will be adjustable from 0 to rated value in stepless manner by means of a voltage setter potentiometer. DC Voltage regulation will be better than 0.5%. The controller will maintain constant voltage at set value under input supply variation and load current variation to keep the structure protected.

In constant current mode the DC output current will be adjustable from 0 to rated value in stepless manner by means of a current setter potentiometer. DC Current regulation will be better than 1%. The controller will keep current limited at set value under input supply variation and load current variation to avoid excessive current to the structure.

AUTOMATIC MODE

The operation of the unit in this mode will be fully automatic and will be controlled by the reference electrode feedback. The unit will automatically maintain reference voltage or pipe to soil potential (P.S.P.) within 10mV of the set value under all conditions. The controller will maintain the structure protected to set PSP value under input supply variation, load current variation and external changes. The unit is capable of accepting up to three reference voltages simultaneously. Reference selector logic selects the lowest (least protected) reference signal and maintains the protection level. Feature is also provided to select one out of three reference electrodes by means of a manually operated reference selector switch.