How do I calculate motor full-load current from nameplate?

For 3-phase: I = P / (√3 × V × cos φ × η). For 1-phase: I = P / (V × cos φ × η). Where P is rated power in watts, V is voltage, cos φ is power factor, and η is efficiency.

What is the difference between nameplate kW and electrical input kW?

Nameplate kW is the mechanical output power at the shaft. Electrical input = nameplate kW / η. The current drawn from the supply is based on the electrical input power, not the shaft output.

What are typical motor efficiency values?

IE1: 82-90%, IE2: 85-92%, IE3: 87-95%, IE4: 90-96%. Efficiency depends on motor size — larger motors are more efficient. Always use the nameplate value if available.

Why does my measured current differ from calculated?

Common reasons: motor not at full load (current is proportional to load), supply voltage differs from nameplate, ambient temperature affects winding resistance, harmonics from VFD supply.

Can I use this for DC motors?

For DC motors: I = P / (V × η). No power factor term since DC has no reactive component. This calculator supports DC mode selection.

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馬達銘牌電流計算器

根據馬達銘牌資料計算滿載電流 (FLA)。支援三相與單相馬達。

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結果

滿載電流 (FLA)

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電氣輸入功率

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視在功率 S

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相數配置

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三相馬達電流

單相馬達電流

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