Figure 6-5, view A, shows the main motor control-ler wiring diagram for the steering system shown infigure 6-3. This wiring diagram can be used to trou-bleshoot, check for proper electrical connections, orcompletely rewire the controller.SCHEMATIC DIAGRAM.—The electrical sche-matic diagram describes the electrical operation of aparticular piece of equipment, circuit, or system. It isnot drawn to scale and usually does not show the relativepositions of the various components. Graphic symbolsfrom ANSI Y32.2 represent all components. Parts andconnections are omitted for simplicity if they are notessential to show how the circuit operates. Figure 6-5,view B, shows the schematic diagram for the steeringsystem main motor controller that has the followingelectrical operation:Assume 450-volt, 3-phase power is available onlines 1L1, 1L2, and 1L3; and 2L1, 2L2 and 2L3; andthe receiver selector is set so that the motors are to idleas standby equipment. Then turn the master switch(MM and SPM push-button station) to the start positionto energize coil 3M. Coil 3M will close main linecontacts 3M, starting the servo pump motor. Whencontacts 3M close, auxiliary contacts 3Ma and 3Mb alsoclose. Contacts 3Ma shunt (bypass) the master switchstart contacts to maintain power to coil 3M after themaster switch is released. When released, the masterswitch spring returns to the run position, closing the runcontacts and opening the start contacts. Turning theswitch to the stop position opens the run contacts.Contacts 3Mb energize latching coil CH, closing con-tacts CH, and energizing coil 1M, which closesmain line contacts 1M to start the main pump motor.(Solenoid latch CH prevents contacts 1M from openingor closing due to high-impact shock.)Before the motors can deliver steering power, thereceiver selector switch must be set to the appropriatereceiver, closing contacts RSSa and RSSb. ContactsRSSa energize coil 2M, which closes contacts 2M tosupply single-phase power to the synchro system. Con-tacts RSSb shunt the start and 3Ma contacts so that incase of a power failure the motors will restart automat-ically upon restoration of power.In case of overload on the main or servo pumpmotor (excessive current through IOL or 3OL),overload contacts 1OL or 3OL will open,de-energizing coil 3M to open line contacts 3M andstop the servo pump motor. When line contacts 3Mopen, contacts 3Ma and 3Mb open, deenergizingFigure 6-4.—Ship's service generator and switchboard interconnections, single-line diagram.6-7
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