Why Do Some Microwaves Reverse Direction When Opened and Closed?

Have you ever noticed your microwave's turntable spinning in the opposite direction when you open and close its door? This seemingly contradictory behavior can be intriguing, but it's actually part of the microwave's design and functionality. Let's delve into the reasons behind this phenomenon.

Motor Design

The primary reason for the turntable's behavior is the design of the motor that drives it. Many microwaves use a reversible motor, which means the motor can rotate in either direction. During normal operation, the motor spins the turntable to ensure even cooking by moving the food around. However, when you open and close the door, the motor may briefly reverse direction before returning to its normal operation.

This brief reverse rotation is often part of the motor's design or the control circuitry. It ensures that the turntable is reset to a consistent position, which is crucial for even cooking. This feature can be beneficial for several reasons:

Preventing food from getting stuck or adhering to the turntable

Maintaining a clean and smooth running turntable for the next use

Adapting to unexpected obstacles or dish placements

This brief reversal is generally harmless and doesn’t affect the overall performance of the microwave. However, if you notice erratic behavior, it’s always a good idea to consult your user manual or contact the manufacturer for further assistance.

User Interface and Mechanical Feedback

Some microwaves are designed with a sophisticated user interface that resets the turntable’s position automatically when the door is opened and closed. This feature ensures that the turntable starts from a consistent position, which can be particularly helpful if you have dishes that don't allow for continuous rotation.

In the case of a large casserole dish, for example, the microwave might reverse direction to oscillate the dish rather than rotate it continuously. This oscillation helps distribute heat more evenly and prevents food from getting stuck on the turntable.

Mechanical feedback is another factor. Models with sensitive mechanical systems may reverse the rotation to clear any obstruction or ensure proper alignment. This feature enhances the overall user experience and ensures that the microwave operates efficiently.

Programming Logic and Cost Considerations

The control board in the microwave has programming logic that dictates the turntable's behavior when interacting with the door. This logic can be designed to enhance user experience and improve cooking efficiency. However, it’s important to note that some microwaves are engineered to have motors that run in a random direction when started.

Most electrical motors used in microwave turntables have starting capacitors or pole shading devices to run in the desired direction. However, making the turntable motor run randomly can save manufacturing costs and make the microwave more affordable without significantly impacting performance.

It’s worth noting that the direction of rotation is not fixed; whether the microwave runs clockwise (CW) or counter-clockwise (CCW) on the next start is a 50/50 deal. This randomness is beneficial as it ensures the motor doesn't wear out in a single direction and adds another layer of cost savings and design flexibility.

Some microwaves will not change direction after each use. The initial direction of rotation is random, which means it could go CW or CCW on the next start. This is a designed feature to ensure the motor doesn't wear out specifically in one direction and adds another layer of cost effectiveness.

In conclusion, the reversing direction of the microwave turntable when opening and closing the door is a carefully considered design feature. It ensures consistent cooking, enhances user experience, and helps to prevent food from getting stuck. If you experience any unusual or persistent issues, consulting the user manual or contacting the manufacturer is always a good step.