Rotatic Rectifier Assemble

The health condition of the diodes can be checked when required as follows :

3.1 The pig tail terminal of each diode is disconnected.

3.2 Using an ohm meter at least 1.5 V source on the appropriate range (say ohms x 1) the resistance of diode between stud and pig tail in both directions is measured. The diodes in good condition will show a low (up to few hundred ohms) resistance in the forward direction and a very high resistance (upto 1 Mega Ohm) in reverse direction. A high resistance in both directions or a low resistance in both directions indicates a faulty diode which should be replaced.

Failure of surge suppressor can be detected by smell and appearance. Failure of fuses (when provided) can be detected by checking its continuity using an AVO meter. sing is necessary.

The faulty diode can be removed from the heat sink after removing the nut at the back of the diode stud & disconnecting the pig tail from its terminal. The heat sink is cleaned well at the diode mounting area and a coating of Silicon grease (eg. AFCO heat sink compound) is applied on diode mounting surface. The diode of corrected polarity is mounted such that the diode base mounts directly on the heat sink without any intervening washers and spacers. The diodes must be tightened against the heat shrink with a torque wrench to a torque of 0.9 kg.m. Care should be taken not to stress its glass seal or the pin to which the pig tail is attached. Pig tail connection is made to the respective terminal.

For replacement surge suppressor change the complete Rectified Assembly itself.

The surge suppressor mounted between the two heat sinks of the rectifier can be removed by dismantling the front plate. The replacement surge suppressor must be identical to the one being replaced and must be assembled with proper polarity in the same way. Care should be taken to see that the insulation washers or tubes provided at various terminals / supports on rectifier assembly are not damaged and that they are assembled as earlier.