Induction Motor Name Plate details

Induction Motor Nameplate Details as per NEMA Standards

Every induction motor comes with a nameplate, which acts as the motor’s identity card. It provides crucial electrical and mechanical information that helps engineers, technicians, and operators select, install, and maintain the motor properly.

The National Electrical Manufacturers Association (NEMA) has defined minimum requirements for motor nameplate data to ensure uniformity across manufacturers.

Below are the standard abbreviations and parameters typically found on induction motor nameplates, along with their importance:

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1. Manufacturer’s Type & Frame Designation

• What it means: Identifies the manufacturer, motor type, and frame size.

• Why it matters: The frame sets mounting dimensions such as foot-hole pattern, shaft diameter, and shaft height. This ensures interchangeability between motors of the same rating from different manufacturers.

• Note: Some dimensions like overall height, conduit-box extension, or special shafts may vary.

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2. Horsepower (HP) / Kilowatt (kW) Output

• Definition: Mechanical output rating of the motor shaft.

• Formula:

  $$HP = \frac{Torque \times Speed}{5250}$$

• Importance: Helps users quickly match motor capacity to load requirements.

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3. Number of Poles

• Relation to Speed:

  $$N_s = \frac{120 \times f}{P}$$

  where $N_s$ = synchronous speed (RPM), $f$ = frequency (Hz), $P$ = poles.

• Example: At 50 Hz, 4 poles → 1500 RPM synchronous speed. With 4% slip, actual motor speed ≈ 1440 RPM.

• Takeaway: More poles = lower motor speed.

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4. Maximum Ambient Temperature (AMB)

• Defines the maximum surrounding temperature for safe operation.

• Commonly inscribed as AMB (°C) on the nameplate.

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5. Insulation Class (INSUL CLASS)

• Indicates winding thermal endurance.

• Common classes: A, B, F, H (higher letter = higher thermal tolerance).

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6. Rated RPM

• Actual motor speed at rated load, considering slip.

• Useful for calculating slip when poles are known.

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7. Frequency (Hz)

• Usually 50 Hz or 60 Hz.

• If multiple frequencies are listed, performance at each frequency must be separately defined.

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8. Number of Phases

• Indicates power supply type: single-phase or three-phase.

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9. Rated Load Current (A)

• Specifies current drawn under rated conditions.

• Often given for different voltages (e.g., star/delta connections).

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10. Voltage (V)

• Motor operating voltage.

• Example: 230/460 V motor can operate on both supply levels, but performance may degrade at lower voltage (e.g., 208 V).

• Note: NEMA standard is 460 V for networks commonly known as 480 V.

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11. Power Factor (PF)

• Ratio of real power (W) to apparent power (VA).

• Full-load PF usually ranges 0.80 – 0.91.

• Closer to unity PF = more efficient use of supplied power.

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12. Efficiency (%)

• Formula:

  $$\eta = \frac{Output}{Input} \times 100$$

• Typical range: 85% – 95%.

• Affected by windage, iron, and stray losses.

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13. Motor Weight

• Important for installation, lifting, and foundation design.

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14. Bearing Information

• Nameplates often list bearing size/designation (e.g., 6309).

• Indicates whether bearings are sealed, shielded, or open.

• Critical for maintenance and replacement planning.

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Why Motor Nameplate Data Matters

• Selection: Helps match motor to load and application.

• Installation: Ensures compatibility with supply voltage, frame size, and mounting.

• Operation: Assures correct running conditions, efficiency, and safety.

• Maintenance: Provides bearing and insulation class data for long-term reliability.

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✅ Key Takeaway: The induction motor nameplate is not just a label — it’s a technical passport. Understanding it allows engineers and operators to make informed decisions about motor installation, performance monitoring, troubleshooting, and replacement.

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⚡ Pro Tip: Always cross-check voltage, frequency, HP/kW, and frame size before replacing or commissioning a motor to avoid costly mismatches.

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