kWからアンペア計算機 ロゴ
kWからアンペア計算機
🚜 モーターサイジング

HPから アンペア 計算機

必要な電流消費量を求めるために、モーターの馬力定格と効率を入力してください。モータースターター、コンタクター、保護ブレーカーのサイジングに不可欠です。

モーター負荷分析

機械的馬力 → 電流

小数点以下
2
計算された電流消費
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A

モーターに必要なフルロードアンペア（FLA）。

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変換式

1機械馬力は正確に746ワットに等しく、これがすべてのHP-アンペア変換の基礎となります。

直流モーター
I = (HP × 746) ÷ (V × Eff)

効率（Eff）はモーターの損失を考慮します。90%効率のモーターは、HP出力が示す以上の電流を消費します。

単相ACモーター群
I = (HP × 746) ÷ (V × Eff × PF)

交流モーターは効率に加えて力率も必要とし、どちらも入力電流に対する実効電力供給を低下させます。

三相ACモーター群
I = (HP × 746) ÷ (√3 × V × Eff × PF)

三相モーターは3つの相に電流を分配します。√3係数（1.732）は線間電圧の関係を考慮したものです。

How to Convert Horsepower to Amps

Horsepower (HP) is a mechanical power rating used to describe motor output capacity. To find the electrical current (amps) a motor draws from the supply, you need to account for the mechanical-to-electrical conversion constant (746 W/HP), the motor's efficiency, and — for AC motors — the power factor. This calculation is essential for sizing motor starters, circuit breakers, cables, and variable frequency drives (VFDs).

Why 746 Watts Per Horsepower?

One mechanical horsepower is defined as exactly 550 foot-pounds per second, which converts to 745.7 watts. This constant is the universal bridge between mechanical and electrical motor ratings. Electric motors are rated in both HP (output) and kW (input), with the difference representing heat losses in the motor windings and core.

Motor Nameplate Data You'll Need

  • HP Rating: The mechanical output power the motor is designed to deliver at full load.
  • Voltage (V): The supply voltage the motor is designed for — often listed as dual voltage (e.g., 230/460V).
  • Efficiency (η): Found on the nameplate as a percentage. Premium-efficiency motors typically run 90–96%.
  • Power Factor (PF): Listed on the nameplate or in the datasheet. Induction motors typically have PF of 0.80–0.92 at full load.
  • Full Load Amps (FLA): The nameplate should also list FLA directly — cross-check your calculated value against this number.

Step-by-Step Conversion

  1. Read the HP: Use the motor's rated output horsepower from the nameplate.
  2. Multiply by 746: Convert HP to watts (1 HP = 746W).
  3. Divide by Voltage: Include the √3 factor for three-phase line voltage.
  4. Apply Efficiency: Divide by motor efficiency as a decimal (e.g., 0.90 for 90%).
  5. Apply Power Factor (AC): Divide by PF for AC motors.
  6. Size Protection at 125%: NEC requires motor branch-circuit conductors rated at 125% of FLA for continuous operation.