A Practical Guide to DC Circuit Breakers for Solar,
This guide is for professional engineers, system designers, and advanced technicians working with modern DC power systems. It
This guide is for professional engineers, system designers, and advanced technicians working with modern DC power systems. It provides insights on selecting, installing, and maintaining DC circuit breakers for solar, battery, and EV systems.
The breaker size can be determined using the formula: Breaker Amps = Inverter Power in Watts ÷ Battery Voltage ÷ Inverter Efficiency × 1.25 For a 12V battery powering a 2000W inverter at 91% efficiency, a circuit breaker rated around 180 amps is recommended. For a 1500W inverter with the same efficiency, a breaker rated around 135 amps is suitable.
The standard rating of a DC circuit breaker is 700A. The battery short-circuit current, per published data for the battery=14,750A. Therefore, the recommended circuit breaker in this example=700A, 65VDC, 15,000 AIC. Moving onto the conductor, we know the cable sizing current=1.25×533=666A.
The battery circuit breaker sizing current = 1.25 x charging current = 1.25 × 400A =500A. The standard rating of DC circuit breaker is 500A. The battery short-circuit current, per published data for the battery = 9,050A Therefore, the recommended circuit breaker in this example=500A, 65VDC, 10,000 AIC.
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