Solar Hot water system (thanks to forum, Warpspeed and others)

Author	Message
phil99 Guru Joined: 11/02/2018 Location: Australia Posts: 3411	Posted: 06:20am 07 Jun 2025         Quote   Very fast PWM frequency will likely mean using a tank temperature sensor to cut the PWM off. An important point. At high frequency the Off time will be too short to extinguish the arc when the thermostat opens. The gate resistor value is too low to have much effect on switching time but should be high enough to dampen resonance between the gate capacitance and PCB track inductance. Without it there is a chance the IGBT will go into RF oscillation and overheat. Data sheet pulse tests are usually done with a high Vce. Here Vce is less than 2V. The frequency is high enough to average the temperature rise so IGBT dissipation needs to be multiplied by the PWM ratio. Eg 50% on time for 5W gives 2.5W.