Enter the net output of the shaft (watts) and the net electrical input to the motor (watts) into the calculator to determine the 3 Phase Motor Efficiency. 

3 Phase Motor Efficiency Formula

The following formula is used to calculate the 3 Phase Motor Efficiency. 

E3p = NO / NI *100
  • Where E3p is the 3 Phase Motor Efficiency (%)
  • NO is the net output of the shaft (watts) 
  • NI is the net electrical input to the motor (watts) 

To calculate the 3 phase motor efficiency, divide the net output of the shaft by the net electrical input to the motor, then multiply by 100.

How to Calculate 3 Phase Motor Efficiency?

The following two example problems outline how to calculate the 3 Phase Motor Efficiency.

Example Problem #1:

  1. First, determine the net output of the shaft (watts). In this example, the net output of the shaft (watts) is given as 500.
  2. Next, determine the net electrical input to the motor (watts). For this problem, the net electrical input to the motor (watts) is given as 2000.
  3. Finally, calculate the 3 Phase Motor Efficiency using the equation above: 

E3p = NO / NI *100

Inserting the values from above and solving the equation: 

E3p = 500 /2000 *100 = 25 (%)


FAQ

What factors can affect the efficiency of a 3 Phase Motor?

Several factors can affect the efficiency of a 3 Phase Motor, including the quality of the motor’s construction, the precision of its windings, the type of materials used, the operating environment (such as temperature and humidity), load variations, and maintenance practices. Efficiency can also be influenced by the motor’s design, such as its size, the presence of cooling systems, and the electrical supply quality.

How can one improve the efficiency of a 3 Phase Motor?

Improving the efficiency of a 3 Phase Motor can be achieved through regular maintenance, ensuring the motor is operating under optimal load conditions, upgrading to a motor with higher efficiency ratings, implementing variable frequency drives (VFDs) to control the motor’s speed according to demand, and optimizing the motor’s operating environment to prevent overheating. Using high-quality lubricants and ensuring proper alignment and installation can also contribute to improved efficiency.

Why is it important to calculate the efficiency of a 3 Phase Motor?

Calculating the efficiency of a 3 Phase Motor is important for several reasons. It helps in determining the motor’s performance and operational cost-effectiveness. High-efficiency motors consume less electrical energy, leading to lower electricity bills and a reduced carbon footprint. Understanding motor efficiency can also aid in selecting the right motor for specific applications, ensuring that it meets energy regulations and standards, and contributes to the overall sustainability of operations.