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High voltage components High voltage components

Summary

  • Failure mode Defects can occur due to poor manufacturing quality.
  • Durability feature Use of certified and tested components to improve reliability.
  • Cost

Good practices

  • Good practicesUse certified and tested components
  • Good practices Good ventilation needed - explained in user guidance

Bad practices

  • Bad practicesAvoid parts that do not meet test standards
  • Bad practices Little or no product placement guidance for customers

Key facts

  • 15% of microwaves are replaced within 3 years because they fail or are unreliable. 

Icon key

  • Failure mode Failure mode
  • Durability features Durability features
  • Cost saving Cost saving
  • Low cost Low cost
  • Cost neutral Cost neutral
  • High cost High cost

Key failure modes

Early Life

  • Defective due to poor design.
  • Poor manufacturing quality.
  • Inappropriate customer product placement restricting air flow.
  • Overheating due to the oven being used empty.
  • Other high voltage components, including the transformer and diode, may fail early if they are defective or of poor quality.

Later in lifetime

  • Magnetrons contain a filament which will burn out earlier than expected if it has not been designed well.
  • Repeated high mains voltage spikes can occur and these will accelerate the failure of magnetron filament.

Specification for improved performance

The specification below provides the recommended improvements needed to improve product durability. They are ranked from bronze to gold based on the effectiveness of the change in improving durability, with bronze being the minimum.

Diode standard test; capacitor endurance test

  • See testing table below for minimum standards.
  • BS EN 136002 quality standard for magnetrons lists the requirements you can specify, but it does not provide recommended values.
  • Mains voltage spikes can be removed by including a varistor in the mains supply circuit.

Cost implications

Improved reliability of components can reduce early returns and improve brand reputation which, in turn, can lower business costs and increase long-term sales.

To calculate overall cost savings for your business, use the WRAP cost/benefit analysis tool (currently in draft form and available on request).

Saving

Neutral

Diode
Negligible additional cost for a better quality component.

Low cost

Capacitor

Good quality requires production experience, expertise and good quality control. Randomly selected products should be tested to confirm reliability.

Transformer

Quality relies on good production expertise and quality.

Magnetron 

These are precision components so must be made with precise dimensions. Good production quality control is also essential.

High cost

Testing to demonstrate performance

The reliability of high voltage magnetrons, diodes, capacitors and transformers can be assessed by testing against standards:

Diodes: Passing standard test EIAJ ED-4701/100 will ensure reliability.        

Capacitors should meet all of the safety requirements of EN 61270-1 but the endurance test in section 5.13 is important for durability.

Transformers do not have a standard durability test but the above method can be used as an indication of reliability.

Thermistors should be tested according to the EN 60335-2-25 standard.

In addition: The fan motor should be run for 15 days uninterrupted. 72 hours later, it should be able to withstand an electrical strength test (as per IEC 60335 Part 2-24 Annex AA Household and similar electrical appliances).