High-Voltage Transformers

30 OVEN SYSTEMS

NOTE: The terminals with the orange dot or the orange wire always go to Terminal 3 on US models.

To verify correct wiring (International), measure the voltage between the taps on FT1 and FT2. The voltage must be 220 VAC (Latin America), 200 VAC (Japan), or 230 VAC (International).

High-voltage transformers are a ferro-resonant design which limits fault currents and minimizes magnetron power changes due to input voltage changes. The high-voltage transformer supplies the high voltage for the Voltage Doubler Circuit. They are controlled via the K2 relay.

Wiring the High-Voltage Transformers

DANGER: Never attempt to wire or measure the secondary voltage values of the

high-voltage transformers with the high-voltage transformers enabled. Lethal voltage will be present.

The proper reinstallation of a high-voltage transformer is critical. Upon removing a high- voltage transformer, make sure to note where each wire was installed. Refer to the oven schematic (page 51) detailing the proper wiring.

As shown in the schematic, transformers are installed mirror opposite and wired 180º out-of- phase. It is essential for longevity that the high- voltage transformers remain 180º out-of-phase. This can be checked by placing a volt meter across terminals T1-1 and T2-1 (primary voltage).

With the microwave system energized, the volt meter will read the incoming voltage (different readings for different electrical installations). If the meter reads 0 VAC, the high-voltage transformers are most likely wired in-phase. As a last check, energize the microwave system and verify the voltages between the taps on each high-voltage transformer.

The wiring issue must be corrected prior to return- ing the oven to service, as the voltages must be:

-NORTH AMERICA: 208 VAC between 1 & 2 and

240 between 1 & 3.

-LATIN AMERICA: 220 VAC

-JAPAN: 200 VAC

-INTERNATIONAL: 230 VAC

NOTE: The terminals with the orange dot/orange wire always go to terminal 3 on USA models.

Testing a Filament or HV Transformer

DANGER: Never attempt to measure the secondary voltage values of the transformers

when they are enabled. Lethal voltage will be present.

1.Disconnect the AC power source and discharge the high-voltage capacitors.

2.Disconnect all the wires in question going to the transformer.

3.Use an ohmmeter to check the impedance of the primary and secondary winding. Refer to the adjacent resistance table to determine if the transformer is OK. If the resistance is different then the table indicates, replace the transformer.

High-Voltage Diodes

The high-voltage diode (Figure 29) is assembled by connecting several 1000-1500 volt semi-conductor diodes in a series to increase the reverse voltage capability. In the circuit, the high-voltage diode conducts to prevent the filament voltage from becoming positive, thus as the high-voltage winding of the transformer goes to 2400 VPK, the high- voltage capacitor is charged to 2400 volts.

Turbo Chef Technologies i5 Wiring the High-Voltage Transformers, High-Voltage Diodes