Excerpts 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

(Excerpt)

18.5 COMMERCIAL MICROWAVE OVENS—DESCRIPTION OF OPERATIONFIGURE 18-5 PANASONIC PRO 1 MODEL REAR VIEW

Figures 18-5 through 18-8 identify the principal components of a typical commercial microwave oven. Following that is a functional block diagram explanation describing the general sequence of operation.— see Figure 18.9 (not shown in this excerpt). Although most 208/240 models employ multiple-magnetron systems, this block diagram shows simply a single magnetron system for clarity. The sequence of operation is essentially the same in multiple systems as in single systems; it is just duplicated.

Electricity from the wall outlet travels through the power cord and enters the microwave through a series of fuse and safety protection circuits. These circuits include various fuses and thermal protectors that are designed to deactivate the oven in the event of an electrical short or if an over-heating condition occurs.

If all systems are normal, electricity passes through to a series of door interlock switches (also called safety switches). When the oven door is closed, the switches are actuated thus providing an electrical path through to the timing, display and control circuits, and, in some models—particularly Amana—to an auto transformer (not shown here) that provides 230V, 208, and 120V to various components. The closed switches also create a voltage path to one side of the blower and stirrer/antenna motors as well as to one side of the high-voltage transformer. The monitor switch (also called the short switch) is a failsafe circuit that monitors the door interlock mechanism. If a switch fails, the monitor switch causes the line fuse to blow.

When the oven timer is set and started, an electrically complementing path is produced through the interlocks and the control circuits to turn on the blower motor, stirrer/antenna motor and cavity lamp. At the same time, a [gate] signal is sent to an electronic switch called a triac, or in some models, to an electromechanical cook relay...

 

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Copyright © 1989-2013 J. Carlton Gallawa . All Rights Reserved Worldwide