page_330

< previous page | page_330 | next page >

Page 330

| Figure 16-17 Contact or disc rectifiers: (A) Assembly and cross section of copper-oxide rectifier stack, and (B) assembly and cross section of selenium rectifier stack (Courtesy, General Electric) |

| such applications as elevators, electrolytic processes, traction systems, steel and textile mills, mines, and other applications where rapid regulation of speed is desirable. |

| The ability to convert ac to dc and dc to ac is taken advantage of by high-voltage electric transmission systems (Fig. 16-18). Such systems eliminate the inductance and capacitance effects of ac circuits. |

| Figure 16-18 Direct current transmission over very long distances. |

| Maintenance |

| Maintenance of water pumps and jackets and coils to prevent corrosion in cooling systems and taking care of vacuum pumps and containers constitute a great part of the maintenance of mercury-arc rectifiers. Dressing and replacement of anodes requires the shutdown of the rectifier and the opening of the container. The unit must then be heated out and evacuated before being restored to service. Cleaning of bushings, and scraping and painting of the container, replacement of gaskets, checking and tightening of water and vacuum lines, lubrication of motors, and other normal routine maintenance activities are all necessary in maintaining mercury-arc rectifiers. Practically no maintenance, except for an occasional dusting, is required for contact-disc rectifiers. For causes and remedies when troubleshooting reactors, capacitors, and rectifiers, see Table 16-1. |

< previous page | page_330 | next page >