Found on all types of electric motors, the motor nameplate provides crucial information about the motor’s construction and performance characteristics.
Although motor standards are established on a country-by-country basis, most motors fall under the two main industry bodies: the International Electrotechnical Commission (IEC) and the National Electric Manufacturers Association (NEMA). Their nameplates adhere to the standards set out by these bodies.
Understanding how to read the nameplate of a motor can help identify faults more accurately, ensure that the right motor is being used for the job, and result in a more efficient service from a motor repair company if there is a fault.
What Information Can Be Found On a Nameplate?
A nameplate contains a wealth of useful information about the motor, including the type, RPM, frame size, and power. In this example, we use the nameplate of a 1LE three-phase electric induction motor manufactured by Siemens .
While the exact layout and format of the motor nameplate depend on the manufacturer and the standards being adhered to (IEC or NEMA), understanding one motor makes it much easier to understand another.
Number of Phases
This indicates the type of power supply for which the motor is designed. Motors can be single-phase or three-phase. In this example, the number is ‘3’, indicating a three-phase motor.
Rated Operating Voltage (Volts)
This shows the voltage at which the motor is designed to operate most efficiently. Motors are typically designed to operate within ±10% of this value. Other parameters shown on the nameplate, including power factor, efficiency, torque, and current, are at the rated voltage and frequency. Operating the motor at a voltage outside this tolerance can lead to different performance outcomes.in our example the we can run the motor at different voltage and speed depend on wiring and line configuration
Efficiency Code or percentage
This shows the percentage of input power that is converted to work output from the motor shaft. The motor will have a “nominal” efficiency shown on the plate, representing the average efficiency. The closer this value is to 100%, the lower the electricity consumption cost will be. The four levels of motor efficiency are:
- IE1 – Standard Efficiency
- IE2 – High Efficiency
- IE3 – Premium Efficiency
- IE4 – Super Premium Efficiency
In our example, the motor shows an IE3 , indicating premium efficiency.
Degree of Protection
The IEC uses a two-digit ingress protection (IP) rating to measure how well the motor is protected from the environment, while NEMA uses an enclosure description of a similar standard. In the example below, an IP of 55 tells us that the motor is ‘protected against dust’ and ‘protected against jets of water from all directions.
Insulation Class
The highest temperature in the motor’s hottest spot significantly impacts the life of the electric motor. The temperature at that spot results from the motor design temperature and the ambient temperature. The insulation class shows the motor’s ability to withstand temperatures over time. Motors have different insulation capabilities, indicated by insulation codes showing their thermal tolerance or ability to survive at a specified temperature for a period. The higher the designated code letter, the greater the heat capability. The highest temperature the material can withstand continuously without degrading or reducing motor life determines the insulation class. IEC specifies five different types of insulation classes:
- Class A – 105°C
- Class E – 120°C
- Class B – 130°C
- Class F – 155°C
- Class H – 180°C
In the example, the motor has an insulation class of F, indicating a thermal tolerance of 155°C.
Temperature Rise
Each insulation class has a maximum motor winding temperature rise and a maximum temperature rating. Additionally, a hot spot temperature rise is specified for motor windings surrounded by other windings.
Frequency (Hz)
This shows the input electricity frequency at which the motor is designed to operate. Typically, motors operate at 50 or 60 Hz. If more than one frequency is marked on the nameplate (like in our example), other parameters that differ at different input frequencies must also be indicated on the nameplate.
Motor Rated Power
kW expresses the motor’s mechanical output rating – its ability to deliver the torque needed for the load at rated speed.
Full Load Speed (RPM)
Full-load speed is the speed at which rated full-load torque is delivered at rated power output. This speed is sometimes called slip-speed or actual rotor speed. In the example nameplate, this is declared as min-1, but it is generally declared in RPM; both measurements are the same.
Rated Operating Current
This corresponds to the rated power output, along with voltage and frequency. The current may deviate from the nameplate amperes if the phases are unbalanced or if the voltage is lower than indicated.
Power Factor
Power factor is indicated on the nameplate as either “PF” or “P.F” or cos φ. Power factor expresses the ratio of active power (W) to apparent power (VA) as a percentage.
Ambient Temperature
The maximum ambient temperature (AMB) indicates the temperature at which the motor can operate and still be within the tolerance of the insulation class at the maximum temperature rise. In this example, the motor’s ambient temperature is 40°C.
Service Factor
This indicates the amount of overload a motor can handle. Electrical motors are often designed to handle a temporary increase in demand, and the motor’s ability to handle these demands is represented by the service factor. For example, a motor with a 1.0 service factor cannot be expected to handle more than its nameplate kW. A motor with a service factor of 1 can safely run with 100 percent load continually
Altitude
This indicates the maximum height above sea level at which the motor will remain within its design temperature rise while meeting all other nameplate data. Below this altitude, the motor may run cooler; above this altitude, the motor may run hotter.
Motor Weight
some nameplates have the weight indicated on them .
Serial Number
This shows the motor’s serial number. As it is unique to the motor, knowing this number can help when liaising with manufacturers or M&E companies about the motor type you have.
Motor Nameplate FAQs
What Is On a Motor Nameplate?
A motor nameplate is a panel affixed to electric motors, providing information about the motor’s construction characteristics and performance. Information typically includes the number of phases, rated operating voltage, service duty, efficiency code, frame size, IP rating, insulation class, and more.
How Do You Read a Nameplate on an Electric Motor?
Motor nameplates can be challenging to understand due to the condensed information in a small space. Generally, each piece of information is preceded by a number, letter, or symbol indicating the meaning of the field. While the layout may vary by manufacturer, the same information is typically provided. Therefore, understanding one motor nameplate makes it easier to understand others.
Read through our blog post to see the exact meaning of each field on a nameplate using a W22 Premium three-phase electric induction motor manufactured by WEG as an example.
What is the Function of a Nameplate?
The function of a motor nameplate is to provide precise information about the motor’s characteristics. This information allows those who work on or maintain the motor to easily recognize its type and characteristics without performing a thorough analysis. As the language is standardized and largely numerical, the same nameplate can be understood by operators worldwide.
