Motor Nameplate Data

The National Electrical Manufacturers Association (NEMA) has developed a standardized system of identifying the important characteristics of motors. The standards do not specify a shape or location for the nameplate, and nameplates may not all contain the same information; but the information that is important for motor selection will be included, see Figure 28.5.

The following list of terms covers some of the information that can be found on motor nameplates:

Manufacturer: The company name and address are included to provide a source of further information. Horsepower: The designed full-load horsepower rating of the motor is given. Serial number: The serial number is included to facilitate the procurement of parts when they are needed. Frame: Standard frame numbers are used to ensure that the motors are interchangeable. If the frame number is the same for two motors, the mounting bolt holes will have the same dimensions. Speed: The speed is in revolutions per minute (rpm). It is the speed at which the motor will operate under a full load. Phase: This indicates whether the motor is designed for single or three phase power. Temperature: This is the maximum ambient temperature for the motor. Service factor: The service factor indicates the safe overload limit of the motor. An SF of 1.20 means that the motor can be operated continuously with a 20% overload without damage. Code letter: The code letter is used to indicate the size of the overload protection device that will be needed. Hertz: This indicates the designed operation frequency of the electrical supply. It is shown as 60 cycles or 60 hertz. Duty rating: Motors will be rated for either continuous or intermittent duty. If the rating is for intermittent duty, the nameplate may also indicate the maximum

Company Information

Hp 1/3

SN 432N5-A

FR 42

RPM 1725

PH 1


SF 1.20

Code J

Hz 60


V 120/240

Amp 6/3

FIGURE 28.5. Typical motor information.

amount of time that the motor can be operated. Exceeding the duty cycle will cause the motor to overheat.

Voltage: The operating voltage for the motor will be indicated. If the nameplate contains only a single value, the motor is not dual voltage.

Amperage: This indicates the current demand at full load. If two numbers are given, it indicates the amperages for the two voltages listed. For example, in Figure 28.5, the amperage is listed as 6/3. This means that when the motor is wired for 120 V, the full load amperage is 6 amps, and it is 3 amps when the motor is wired for 240 V.

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