Designing Adjustable 1-Phase Square Wave Generator (0-500V, 25A) from 3-Phase Input

The discussion focuses on designing an adjustable single-phase bipolar square wave generator with an output of up to 500V and 25A, powered from a 3-phase 380V input via an 8.1kVA autotransformer. The load is purely resistive. Key design considerations include the use of a high-voltage H-bridge switching stage, preferably with fast-switching MOSFETs or possibly IGBTs, to generate the square wave. A linked circuit simulation demonstrates half of an H-bridge, emphasizing correct phasing and the need for high-voltage transistors. Frequency control can be achieved using a 556 dual timer IC to generate 180° out-of-phase square waves for driving the H-bridge, with adjustable frequency via a variable resistor. Alternative approaches suggest using SCRs (silicon controlled rectifiers) or paralleled solid-state relays (SSRs) for switching, especially at low frequencies (up to 100 Hz), due to their suitability for high current and voltage and reduced conduction losses. However, SCRs pose challenges in turn-off control, making SSRs a more practical option. Dead time management in the H-bridge is critical to prevent shoot-through currents that can damage devices. The power supply requirement is significant, with an estimated minimum of 6.25 kW at 50% duty cycle, plus losses. A referenced article on discrete MOSFET-based solid-state relays provides additional design insights. Safety warnings highlight the high voltages and currents involved, requiring qualified handling.
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