What size circuit breakers and cables?
Thread Content
Hello everyone, I have a steamer for making mantou here, with a power rating of 24KW and it operates on 380V three-phase electricity. What size circuit breaker and aluminum cable should be used? Currently, using a 60A circuit breaker and 10MM2 aluminum cable causes overheating. The circuit breakers are from Chint, and 6 of them have already been replaced due to burning out. How can I avoid burning it out? Thank you all!
To achieve both savings and safety. It’s best to use a 60A circuit breaker with a leakage protection function; it’s a heater, not a motor, right? It’s the three-phase star connection. Multiple strands of soft wire with a cross-sectional area of 10 m² (copper) are covered with copper connectors on the terminal posts to enhance the skin effect; these wires are also connected using copper-aluminum connectors and fixed in a junction box mounted on the wall. Copper connectors should be installed at both the source and the load end. Add a ground to the enclosure.
Since the steamed bun maker is a pure resistive load, the current I is equal to power P divided by voltage V: 24000/380 = 63.16 A. Therefore, the minimum rating for a circuit breaker should be 80A or 100A. The cable should use a copper core with a cross-sectional area of 16 square millimeters ； For the aluminum core, 25 square millimeters is a suitable choice. As mentioned above, it’s best to choose a circuit breaker with leakage protection. The exterior of the steamed bun maker must be grounded. It’s necessary!
Sit down and learn *electrical knowledge – steamed bun maker – pure resistive load.
Choose an air circuit breaker of 80A, and select a copper-core cable with a cross-sectional area of 16 square millimeters
Everyone’s discussions have been very helpful to me; thank you all here. :):):):):)
For a three-phase load, this way of calculating the current is incorrect, right? I = P/380/1.732/power factor; the power factor for a resistive load should be 1. Therefore, the current is 36.45 A, so a 60A circuit breaker is suitable! Additionally, when using three-core copper wires of types RV or BVV, at an ambient temperature of 30 degrees, a current of 48A is permissible for 10mm2 wires; therefore, a 10MM2 copper wire is sufficient
When it’s in operation, buy a clamp ammeter to measure the current; that way you’ll know. Electricians also need this type of meter!
You’re right; I missed one square root of 3. Thanks for the reminder.