Part 3 – Understanding NEMA Motor Nameplate Data and Marking

Electrical Technology

How to Read NEMA Motor Nameplates Data Printed on It for Motor Circuits?

What is NEMA?

NEMA (National Electrical Manufacturers Association) is a U.S.-based trade association that develops and publishes technical standards for electrical equipment, including motors, enclosures, wiring devices, and industrial control systems. Founded in 1926, NEMA sets guidelines to ensure safety, compatibility, and performance across various electrical products used in residential, commercial, and industrial applications.

NEMA establishes industry standards for motor design, frame sizes, efficiency ratings, and performance specifications to ensure interchangeability and reliability in accordance with National Electrical Code (NEC) and regulatory bodies like UL (Underwriters Laboratories) and ANSI (American National Standards Institute).

Common NEMA Standards for electric motors are as follow:

According to NEMA, a typical electrical motor nameplate or label and marked data printed on it must show:

It is important to understand the specifications, features, and characteristics of an electric motor before purchasing one for residential or commercial applications. This information is printed on the motor’s nameplate, helping to ensure the right motor is selected for a specific application.

How to Read a Typical NEMA Motor Nameplate Rating and Data?

A NEMA motor nameplate contains motor load circuit and general information that helps in selecting, installing, and maintaining an electric motor. Each parameter provides details about the motor’s electrical, mechanical, and thermal characteristics.

How to Read a Motor Nameplate Data

Below is a detailed explanation of each nameplate parameter based on the given nameplate markings for Baldor Reliance Super-E Motor (Model EM3615T).

1 – Manufacturer

The nameplate will display the manufacturer’s name and a unique model or catalog number. This helps in identifying the motor for replacements, specifications, or warranty purposes.

2 – Horsepower (HP)

This indicates the mechanical power output of the motor. One HP equals 746 watts, meaning a 5 HP motor can deliver 3,730 watts of mechanical power. It determines the motor’s power rating and capability to drive loads.

3 – Voltage (V)

The rated operating voltage of the motor, such as 115V, 208V, 230V, 460V, or dual-voltage (e.g., 230/460V). Using a voltage outside the specified range can damage the motor or reduce efficiency.

The operating voltages from the nameplate data:

VOLTS: 208-230/460 → The motor can operate at multiple voltages:

As the motor is operable at multiple voltage levels, its wiring installation should be done according to the diagram provided on the nameplate for low-voltage and high-voltage connections.

4 – Full Load Amps (FLA)

FLA represents the current drawn when the motor is operating at full rated load and voltage under full load conditions. It is essential for sizing circuit breakers, fuses, and wiring.

The FLA values from the nameplate data:

AMPS: 13.9-13.4/6.7 → The current drawn depends on the voltage:

Good to know: FLA (Full Load Amperes) and FLC (Full Load Current) are not the same. The difference lies in how they are defined and calculated, particularly in accordance with NEC standards for motor circuits.

5 – Locked Rotor Code (Code Letter)

A letter (from A through V) for LRC represents the inrush current during startup. Motors with a high inrush current require careful circuit protection. The estimated value of locked-rotor current (RLC) are determined using NEC Table 430.7(B).

For instance:

6 – Frequency (Hz)

The motor’s frequency rating, typically 60 Hz in North America and 50 Hz in other regions. Running a motor on the wrong frequency can alter its speed and performance.

7 – Phase

Specifies whether the motor operates on single-phase or three-phase power. Single-phase motors are common in residential applications, while three-phase motors are used in industrial settings for better efficiency and power handling.

8 – Speed in RPM (Revolutions Per Minute)

Indicates the motor’s rotational speed per minute at full load. It depends on the number of poles and power frequency (e.g., a 2-pole motor at 60 Hz runs at ~3,600 revolutions per minute (RPM), while a 4-pole motor runs at ~1,800 RPM).

9 – NEMA Frame Size

The frame size (e.g., 56, 143T, 184T) defines the motor’s physical dimensions, shaft diameter, and mounting hole locations and requirements. Motors with the same frame size are interchangeable without major modifications.

10 – Service Factor (SF)

Service Factor S.F or SER.F) is a multiplier that indicates the motor’s ability to operate beyond its rated horsepower for short durations. For example, a 1.15 SF motor can safely handle 15% more load beyond its rated HP without overheating.

The value of service factor is considered when sizing an overload protection for the motor circuit based on the FLA mentioned on the motor’s nameplate (NEC-430.32(A)(1).

11 – Insulation Class

Defines the thermal resistance of the motor’s insulation. Common classes are:

Higher classes allow the motor to operate at higher temperatures without degradation.

12 – Design Letter (DES.)

The letter indicates the torque/speed characteristics of the motor.

Generally, they are not indicated for motors larger than 500 HP at 1800 RPM, variable speed applications, and motors across the line starting. Some common NEMA design marks are as follow:

13 – NEMA NOM. – Efficiency (%) & P.F

Represents the ratio of mechanical power output to electrical power input. Higher efficiency motors consume less energy, reducing operating costs. For instance: NEMA NOM. EFF.: 89.5% → The motor operates at 89.5% efficiency.

Power Factor (PF)

Power factor (P.F) is the ratio of real power (watts) to apparent power (volt-amperes), typically between 0.7 and 0.95. A higher power factor indicates better electrical efficiency. For instance:

14 – Temperature Rating and Duty Class

The motor’s maximum rated operating ambient temperature (usually 40°C) and altitude limit (typically 1,000 meters or 3,300 feet above sea level). Higher temperatures or altitudes require derating. The Cont. Indicates whether the motor is designed for continuous duty (CONT) (running continuously at full load) or intermittent duty, where it operates for short periods with rest intervals.

Indicates whether the motor is designed for continuous duty (CONT) (running continuously at full load) or intermittent duty, where it operates for short periods with rest intervals.

15 – Certified Compliant Number (CC)

This number is printed on all motors that comply with the NEMA Premium Efficiency Specification. They are helpful to select an energy efficient motor to lower the power consumption and reduced electricity bill.

16 – Bearings & Lubrication

Specifies the type of bearings (ball or sleeve bearings) and recommended lubrication frequency for maintenance. For instance:

17 – Enclosure Type (NEMA Code)

ENCL. defines the motor’s protection level against environmental factors:

18 – Serial Number, Catalog Number and Specifications

Unique identifiers for tracking manufacturing date, warranty claims, and part replacements. For instance;

19 – Certification Marks

Additional Motor Nameplate Data (Not Shown in the Figure)

Understanding Electric Motor Nameplate

In addition to the standard specifications, some motor nameplates include additional useful information, such as:

Series Overview: Motor Circuit Calculations

Resources & Tutorials:

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