Introduction: Motor nameplates are a critical source of information for anyone dealing with industrial motors. These metal tags attached to the motors provide a wealth of data for the motor’s selection, installation, maintenance, and troubleshooting. This blog post will delve into the details of motor nameplate data, helping you understand and utilize this information effectively.

What is Motor Nameplate Data?

Motor nameplate data refers to the technical specifications and operational parameters engraved or printed on a plate attached to a motor. This data includes, but is not limited to, the motor’s power output, speed, voltage, current, and efficiency ratings.

Why is Motor Nameplate Data Important?

Understanding the data on a motor’s nameplate is crucial for several reasons:

• Selection: Ensures that the motor meets the specific requirements of an application.
• Installation: Provides necessary information for correct electrical connections and physical mounting.
• Maintenance: Helps plan preventive maintenance schedules and identify replacement parts.
• Troubleshooting: Assists in diagnosing problems and taking corrective actions.

The motor nameplate contains a wealth of information crucial for understanding the motor’s specifications and ensuring it is used correctly. Here’s a detailed explanation of the ratings and codes typically found on a motor nameplate:

• Manufacturer’s Logo: Identifies the maker of the motor.
• Motor Series: Indicates the model or series to which the motor belongs.
• Efficiency Class: Shows the motor’s efficiency rating, such as IE2, a high-efficiency class.
• Frame Size: Specifies the physical dimensions and mounting interface of the motor.
• Insulation Class: This class denotes the thermal tolerance of the motor’s insulation material. Class F is rated for higher temperatures than Class B or A.
• IP Rating: The Ingress Protection rating indicates the level of protection against solid objects and liquids. IP55 means the motor is dust-protected and protected against water jets from any direction.
• Duty Cycle Type: S1 indicates continuous operation at a constant load.
• Voltage Ratings and Power Outputs: This section lists the motor’s voltages and the corresponding power output in kilowatts (kW) at different frequencies (Hz).
• Speed: Given in revolutions per minute (RPM), it indicates how fast the motor spins at a specific voltage and frequency.
• Service Factor: A multiplier that indicates how much over the motor’s nominal rating it can be loaded under certain conditions.
• Rated Current: The current, in amperes (A), that the motor is designed to draw under full-load conditions.
• Locked Rotor Code Letter: This letter indicates the starting kVA required per horsepower when the rotor is locked.
• Bearing Sizes: Indicates the size of the bearings used in the motor.
• Additional Codes:
  • CE Marking: Signifies conformity with European health, safety, and environmental protection standards.
  • NEMA Nom Eff %: The nominal efficiency percentage as per NEMA standards.
  • Certification Marks: Like CSA (Canadian Standards Association) and UR (Underwriters Laboratories), indicating compliance with respective standards.
  • Model Number: Unique identifier for the motor.
  • Serial Number: A unique number assigned to each motor for identification.
  • Weight: The mass of the motor.
  • Design Letter: Indicates the torque and current characteristics of the motor.
  • Ambient Temperature Rating: The maximum ambient temperature in which the motor can operate without overheating.
  • Altitude Rating: The maximum altitude the motor can operate without derating.
  • Thermal Protection Type: The type of thermal protection used in the motor.
  • Insulation System Classification: The temperature rating of the insulation system used in the motor.

Each of these details helps select the right motor for an application, understand its operating limits, and ensure proper maintenance.

The locked rotor code letter on a motor nameplate is important because it provides information about the starting kVA (kilovolt-ampere) required by the motor when the rotor is not spinning. This code is a NEMA (National Electrical Manufacturers Association) designation that categorizes motors based on the ratio of locked rotor kVA per horsepower. The code consists of letters from A to V, each representing a range of kVA values.

For example, a motor with a locked rotor code letter “G” typically has a locked rotor kVA range of 5.6 to 6.29 kVA per horsepower. The farther away from the letter A, the higher the inrush current per horsepower at startup. This information is crucial for designing starting circuits, selecting protective devices, and ensuring the power supply can handle the inrush current when the motor starts.

The code letters represent the kVA per horsepower as follows:

-Please remember the following ranges:

A: 0 – 3.14

B: 3.15 – 3.55

C: 3.55 – 3.99

D: 4.0 – 4.49

E: 4.5 – 4.99

F: 5.0 – 5.59

G: 5.6 – 6.29

H: 6.3 – 7.09

… and so on up to V.

Understanding the locked rotor code is essential for applications where the motor will experience heavy loads at startup or the electrical supply system must meet stringent requirements1.