Скачать или смотреть INSULATION TESTING for Motors & Compressors | Step for Megger Test Explained Low-Voltage to 11 kV

Learn how to perform insulation resistance testing for motors, compressors, and rotating equipment using a megohmmeter (megger). This video covers the concept, testing methods for low- and high-voltage motors, air/refrigeration compressors, and predictive maintenance trending. Includes practical examples, IEEE 43 / IEC 60034 standards, and clear formulas you can apply directly in field maintenance and reliability programs. Perfect for mechanical, electrical, and maintenance engineers working with industrial systems.

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🟦 Slide 1 – Concept & Purpose of Insulation Testing

Purpose: Detect insulation degradation before failure.
Test Tool: Megohmmeter (500–1000 V DC).
Formula: Resistance (MΩ) = Voltage (V) / Leakage Current (μA)
Example: (500 V / 10 μA) = 50 MΩ
Standard Reference: IEEE 43 / IEC 60034

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🟩 Slide 2 – Test on Low-Voltage Motor (≤ 690 V)

Steps: 1️⃣ Lockout–Tagout (LOTO) 2️⃣ Disconnect cables 3️⃣ Apply 500 V DC 4️⃣ Measure each phase 5️⃣ Compare baseline.
Formula: Minimum Insulation (MΩ) = (Voltage in kV × 1) + 1
Example: 690 V → 0.69 kV × 1 + 1 = 1.69 MΩ

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🟧 Slide 3 – Test on Medium / High-Voltage Motor (3.3 – 11 kV)

Procedure: Discharge motor before and after test → Measure Polarization Index.
Formula: Polarization Index (PI) = R (10 min) / R (1 min)
Example: R1 = 50 MΩ, R10 = 120 MΩ → PI = 2.4 ✅
Interpretation: PI ≥ 2.0 = Good, 1.0–1.5 = Caution

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🟥 Slide 4 – Test on Air / Refrigeration Compressors

Disconnect control wiring and test windings to ground / inter-winding resistance.
Acceptable: ≥ 20 MΩ (dry).
Formula: I = V / R
Example: 500 V / 25 MΩ = 20 μA leakage
If less 10 MΩ → heat or dry before restart.

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🟨 Slide 5 – Evaluation & Trend Monitoring

Monitor resistance monthly or quarterly to predict failure.
Formula: Degradation Rate (%) = [(Rprev − Rcurr) / Rprev] × 100
Example: (100 − 80) / 100 × 100 = 20 %
Integrate data into CMMS / PdM dashboard for early warning.

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