Ultra-fast switches- a new element for medium voltage fault current limiting switchgear

Finite element analysis and efficiency improvement of the Thomson coil actuator

“…Electrical to mechanical energy conversion efficiency is calculated in this assessment as the kinetic energy to electrical energy spent ratio after the 2 milliseconds of interest. The efficiency in percent can be calculated at any instant using (5).…”

“…In addition, a single semiconductor device is not able to withstand the full voltage and current rating required, therefore a series and parallel arrangement of many semiconductor switches is required to achieve HVDC circuit breaker ratings, increasing the DC breaker cost. On the other hand low conduction loss HVDC breaker alternatives, such as hybrid [2] and mechanical [5] breakers, use mechanically separable contacts to provide voltage isolation while enabling low conduction loss under normal conditions. Unfortunately hybrid and mechanical breakers are slow in comparison to solid-state breakers due to the inertia of the mechanical part.…”

“…Due to the direction of the induced currents, a repulsive magnetic force occurs between armature and coil. Using this principle opening speeds in excess of 20m/s achieved over a time of 2 milliseconds have been reported [5,6,7,8], and consequently TC designs are claimed to provide the high acceleration required for HVDC breaker applications. The main drawback of this actuation mechanism is the low efficiency, typically in the 5% range [5,6], although recent research reports efficiencies as high as 14% for loaded mechanisms [9].…”

“…Using this principle opening speeds in excess of 20m/s achieved over a time of 2 milliseconds have been reported [5,6,7,8], and consequently TC designs are claimed to provide the high acceleration required for HVDC breaker applications. The main drawback of this actuation mechanism is the low efficiency, typically in the 5% range [5,6], although recent research reports efficiencies as high as 14% for loaded mechanisms [9]. As a consequence of the TC actuator low efficiency, relatively large and expensive ancillary components (such as energy storage capacitors) are required to ensure proper operation of the device, imposing challenges in operation, reliability and maintenance of the system.…”

Modelling Thomson Coils With Axis-Symmetric Problems: Practical Accuracy Considerations

“…OR applications that require ultra-fast actuation, the preferred actuator design is based on the Thomson Coil (TC) [1][2][3][4][5]. The TC comprises a planar coil and an electrically conductive disc armature, placed in close proximity and parallel to the coil, Fig.…”