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馬達轉差率與實際轉速計算機
計算感應馬達的同步轉速、實際 RPM、滑差百分比及滑差頻率。輸入 RPM 以計算滑差，或輸入滑差以計算 RPM。
結果
同步轉速
感應馬達中旋轉磁場的同步轉速：
- f — 電源頻率 (Hz)：50 Hz 或 60 Hz
- P — 極數
轉差率
馬達滑差是同步轉速與實際轉子轉速之間的相對差異：
由滑差計算實際轉速
轉差頻率
轉子中感應電流的頻率：
同步轉速參考
| 極數 | 50 Hz (RPM) | 60 Hz (RPM) |
|---|---|---|
| 2 | 3000 | 3600 |
| 4 | 1500 | 1800 |
| 6 | 1000 | 1200 |
| 8 | 750 | 900 |
| 10 | 600 | 720 |
| 12 | 500 | 600 |
實務範例
已知： f = 50 Hz, P = 4 極, 銘牌 RPM = 1450
Ns = 120 × 50 / 4 = 1500 RPM
s = (1500 − 1450) / 1500 × 100 = 3.33%
f轉差率 = 3.33/100 × 50 = 1.67 Hz
f轉子 = s × f = 0.0333 × 50 = 1.67 Hz
提示： 滑差頻率是振動分析中的關鍵指標。在電源頻率周圍出現 2 倍滑差頻率 (2 × f轉差率) 的邊帶特徵振動，通常表示感應馬達存在轉子導條問題。
⚠️ 注意： 銘牌 RPM 代表滿載轉速。在部分負載下，實際轉速會較高（滑差較低）。在無負載時，滑差通常為 0.5–1%。
Motor slip is the difference between the synchronous speed of the rotating magnetic field and the actual rotor speed in an induction motor, expressed as a percentage:
s = (Ns − N) / Ns × 100%
Slip is essential for torque production. Without relative motion between the rotor and the magnetic field, no voltage would be induced in the rotor conductors, and no torque would be generated.
Typical full-load slip values:
- 1–3% — Large motors (>100 kW)
- 2–5% — Standard motors (NEMA Design B)
- 3–7% — Small motors (fractional HP)
- 5–13% — High-slip motors (NEMA Design D)
At no load, slip is typically 0.5–1%. Slip increases proportionally with load up to the breakdown torque point.
Slip exists because an induction motor works on the principle of electromagnetic induction:
- The stator creates a rotating magnetic field at synchronous speed Ns
- This field must "cut" the rotor conductors to induce a voltage (Faraday's Law)
- The induced voltage drives current through the rotor bars, creating rotor magnetic field
- Interaction of stator and rotor fields produces torque
If the rotor reached synchronous speed, there would be zero relative motion, zero induced EMF, zero rotor current, and zero torque. Therefore, the rotor always runs slightly slower than the field.
Load and slip are directly related:
- No load: Very low slip (0.5–1%), motor runs near synchronous speed
- Increasing load: Motor slows down → slip increases → more rotor current → more torque
- Full load: Slip reaches nameplate value (typically 2–5%)
- Overload: Slip continues to increase up to breakdown torque (typically 2–3× rated torque)
- Beyond breakdown: Motor stalls — torque decreases rapidly with increasing slip
The slip-torque curve is approximately linear from no-load to full-load for normal operation.
Motor slip can be measured using several methods:
- Tachometer: Measure actual RPM with contact or optical tachometer and compare to synchronous speed
- Stroboscope: Flash at line frequency — if rotor appears to slowly rotate backward, the slow rotation rate equals slip speed
- Vibration analysis: Detect slip frequency sidebands around line frequency in the vibration spectrum (2× slip frequency sidebands indicate rotor issues)
- Nameplate method: Use nameplate RPM as full-load speed and calculate: s = (Ns − Nnameplate) / Ns
For vibration analysts, monitoring slip frequency is critical for detecting broken rotor bars and rotor eccentricity.
本頁所述的操作流程由 Vibromera 團隊使用 Balanset-1A（一款用於現場轉子平衡的便攜式雙通道動平衡儀及振動分析儀）開發並經過實地測試。
專業現場動平衡儀器與軟體。透過振動分析偵測轉子導條缺陷與馬達故障。已應用於 50 多個國家。
Nikolai Shelkovenko
Nikolai Shelkovenko是一名振動分析工程師，也是Vibromera的創辦人兼執行長。 15年多來，他一直在現場——而非在試驗台上——為旋轉設備進行動平衡校正：粉碎機、工業風機、破碎機、離心機、軸與主軸。正是這些實際工作催生了Balanset系列儀器——它們被設計為一種專業人員可以隨身攜帶到機器旁、在現場獨立使用的工具，而非實驗室設備。 Vibromera成立於2017年，自2023年起總部設於葡萄牙波爾圖。Balanset系列產品的研發、組裝與支援均在此完成。旗艦產品是Balanset-1A，一款用於單平面及雙平面動平衡校正與振動診斷的可攜式分析儀。 Nikolai親自參與客戶支援工作，處理各種棘手的動平衡校正案例，並參與軟體開發。他以任何語言為全球客戶提供服務。
