Exerpts from the CD-ROM:
THE COMPLETE MICROWAVE OVEN SERVICE HANDBOOK: Operation, Maintenance, Troubleshooting and Repair
Copyright © 1989-2013 J. Carlton Gallawa . All Rights Reserved Worldwide

Chapter Eight: Control Systems (continued)

8.13.1 System Operation

The representative schematics of Figure 8-38 illustrate the typical operation of a triac-controlled system. Notice that the schematic symbol for a triac resembles the two SCRs connected in the antiparallel configuration shown earlier in Figure 8-34. A triac is essentially two silicone rectifiers fabricated in an antiparallel arrangement with a common gate. To gain a better understanding of an entire operating system, the explanation to follow is of a typical triac-controlled circuit in the context of a schematic that includes all the associated components necessary for an actual working system. Unfamiliar components that are not explained at this time will be elaborated upon in subsequent chapters. Refer to Figure 8-38.

SCHEMATIC #1
With the oven plugged into a standard 115 VAC grounded outlet, voltage is applied through the 15 amp FUSE to the primary of the LOW-VOLTAGE TRANSFORMER, which sup-plies the operating voltages to the control circuitry. The time-of-day clock operates and the CONTROL PANEL is ready to receive instructions.

The oven door is then opened and the CAVITY LIGHT illumi-nates with current supplied through the normally closed (NC) contacts of the LOWER DOOR INTERLOCK SWITCH

 

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