Industrial Microwaves: Magnetron Tubes vs. Solid State

Crescend RF

Historically, every microwave heating device, from a home microwave oven to a large industrial system, has been powered by a magnetron tube. First developed in the 1940s, and have remained functionally the same ever since. But many say that solid state is the microwave technology of the future, especially when it comes to drying and thermal processing applications in food, biomass, engineered materials, plasma systems, precision drying and laboratory use. That’s because magnetrons, while highly efficient in converting electric power into microwave energy, also have many disadvantages when compared to solid state microwave technology.

The Solid State Cost and Reliability Advantage

Magnetron tubes have a lifetime of only a few thousand hours—from 2,000 hours up to 8,000 hours depending on the tube. Magnetron tubes are also difficult to troubleshoot and service, which can result in costly downtime and repairs. Solid state microwave systems, however, are designed to last more than 30 years—over 500,000 hours  In all, the long term total cost of ownership can be significantly less for solid state microwave systems when compared to magnetron tubes.

The Solid State Heating Advantage

Microwave ovens and applicators have hot and cold spots due to the random interaction of waves.  Magnetrons, which operate on a single fixed frequency, can’t do much to avoid this problem. This is why industrial microwave systems use rotating antennas (and why many home microwave ovens have turntables)—for more even heating.  Even so, the results are inconsistent.

Solid state microwave generators can vary frequency when they are operating.  This causes the hot and cold spots to move around.  This effectively acts as a method of “electronic stirring.” The end result is much better heating uniformity.

The PrecisePower™ Advantage

Crescend’s proprietary Windows-based PrecisePower™ software suite provides even greater advantages for solid state microwave systems, including nearly instantaneous and extremely accurate (<0.1%) power control. Various frequency control mode are provided including single-frequency, auto tuning, and band  sweeping.  Its built-in analytic features couple real-time monitoring  with automatic adjustments in operating frequencies or ranges of frequencies. Distributed, dedicated high speed microcontrollers constantly monitor and adjust key operating parameters to provide targeted delivery of energy, with complete frequency, power and phase control.

Another new PrecisePower™ capability is its high speed pulsed mode operation. This means the microwave can be switched at a frequency of up to 10 KHz with a variable duty cycle. Research suggests that pulsed modes may have significant benefits in certain drying, plasma generation and other applications.

Crescend’s solid state microwave solutions deliver a level of precision, performance and reliability that has never been previously possible.

Magnetrons Solid State Microwaves
Control Energy levels alternate between full and zero power only. Heating is uneven. High precision solid state microwave power can be tailored to the frequency, phase and output power needed.
Energy Efficiency Cannot measure or adapt energy use Automatically adjusts the coupling of the microwave energy to the load, ensuring maximum energy transfer, resulting in lower power needs.
Durability Over three-to-four years, a magnetron will typically lose 30% of its power. Designed to last 20-30 years.
Consistency Noisy and unstable; uses dangerous multi-kV power supplies. Uses pure, safe and low voltage DC power.

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