The core of selecting a voltage protector lies in matching it based on both the appliance's load characteristics (resistive or inductive) and its rated power (which determines the rated current). The following provides clear selection guidance by combining specific power and ampere values.
For resistive load appliances:
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Appliances with a power of 2000 watts or less, such as an 1800W electric kettle or a 1500W electric skillet, are typically suitable for protectors rated at 12A, 13A, or 15A.
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Appliances with a power between 2001 watts and 3500 watts, such as a 2000W electric heater or a 3500W large electric oven, are recommended to be matched with a 20A protector.
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Appliances with a power of 3501 watts or more, such as an 8500W instant electric water heater, must use a dedicated protector rated no less than 30A and require an independent circuit.
For inductive load appliances:
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Appliances with a power of 2000 watts or less, such as a 1300W microwave oven or a 1200W blender, are recommended to use protectors rated between 15A and 20A.
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Appliances with a power between 2001 watts and 3500 watts, such as a 2500W air conditioner or a 2200W washing machine, should be matched with a 20A protector.
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Appliances with a power of 3501 watts or more, such as a 5000W central air conditioner, require a 30A protector.
1. Selecting Protectors for Resistive Load Appliances
The current in resistive loads is stable. Selection is primarily based on the continuous operating current calculated from the rated power, with some allowance.
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Calculation and Selection Examples:
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1800W Electric Kettle: Operating current ≈
1800W / 220V ≈ 8.2A. Categorizing it in the 12A protection group is safe and sufficient, providing about 50% margin to avoid nuisance tripping caused by minor voltage fluctuations. -
3500W Large Electric Oven: Operating current ≈
3500W / 220V ≈ 15.9A. Categorizing it under a 20A protector meets the rated operating requirement and provides a safety margin for potential line heating during prolonged high-temperature operation. -
8500W Instant Electric Water Heater: Operating current is as high as
8500W / 220V ≈ 38.6A. It is mandatory to use a dedicated protector rated ≥40A on an independent circuit, which exceeds the standard 30A rating.
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Technical Points:
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Auto-Reset Function: For frequently used kitchen resistive appliances like electric kettles and skillets, it is recommended to choose an over/under-voltage protector with an auto-reset function to avoid the inconvenience of manual resetting after brief voltage anomalies.
2. Selecting Protectors for Inductive Load Appliances
The key to selecting protectors for inductive loads is that the protector's rated current must withstand the appliance's continuous operating current, and its performance must be capable of handling the startup surge.
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Calculation and Selection Examples (Focus on Startup Current):
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1300W Microwave Oven (contains transformer and motor): Rated current ≈ 5.9A, but its magnetron and motor can generate multiples of this current upon startup. Although its power falls within the "13A group," for safety, it is recommended to configure it with a 15A or higher protector that has a fast response.
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2500W Wall-Mounted Air Conditioner: Rated current ≈ 11.4A. However, the instantaneous startup current of its compressor can reach 5-7 times the rated value (approx. 57-80A). Although steady-state operation only requires 11.4A, the 20A protector configured for it must have a "Type D" or "Type K" tripping curve. These circuit breakers have a higher magnetic trip threshold, allowing them to "tolerate" short startup surges without nuisance tripping.
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5000W Central Air Conditioner Outdoor Unit: Rated current ≈ 22.7A, with a very high startup surge. A 30A motor-dedicated protector must be used, ensuring both the wiring and the protector can withstand this surge.
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Technical Points:
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Response Speed: It is essential to choose a protector with a very fast response time (≤10ns) to effectively clamp surge voltages.
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Specialized Circuit Breaker: When wiring motor-driven appliances like air conditioners and washing machines, always choose a Type D or Type K Miniature Circuit Breaker (MCB), not a general-purpose Type C. This is key to preventing tripping during startup.
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