# Calculate the Motor Efficiency when?

• Totter
In summary, the motor efficiency is 82.85%, the generator efficiency can be calculated using the input power of the generator, and the overall efficiency would depend on the individual efficiencies of the motor and generator.
Totter
An electric motor drives an electric generator.The 2hp motor draws 15A from a 120V D.C source and the generator supplies 5A to a 48Ohm LOAD. It is given that 1hp= 745.7W

Calculate the motor efficiency.
Calculate the generator efficiency.
Calculate overall efficiency.

Ok soo I went forward and did this.
Since 1hp = 745.7Watt I assumed that the motor would be going at 2x745.7W = 1491.4W .
So if you take the P = I.V and you insert 15A.120V = 1800W
So using n = Po/Pin for Efficiency 1491.4/1800 *100 = 82.85% efficiency.
Not sure if this is correct but now?
I can say P = I^2 / R and get the Watt but to what comparison? Which Po and which Pin ??

Totter said:
An electric motor drives an electric generator.The 2hp motor draws 15A from a 120V D.C source and the generator supplies 5A to a 48Ohm LOAD. It is given that 1hp= 745.7W

Calculate the motor efficiency.
Calculate the generator efficiency.
Calculate overall efficiency.

Ok soo I went forward and did this.
Since 1hp = 745.7Watt I assumed that the motor would be going at 2x745.7W = 1491.4W .
So if you take the P = I.V and you insert 15A.120V = 1800W
So using n = Po/Pin for Efficiency 1491.4/1800 *100 = 82.85% efficiency.
Ignoring any rounding differences/errors, yes, that looks correct to me.
Totter said:
I can say P = I^2 / R and get the Watt but to what comparison? Which Po and which Pin ??
To calculate the generator's efficiency, just stick with the generator. What's the input power of the generator?

(Hint: the problem statement says, "An electric motor drives an electric generator." I'm pretty sure you should assume no losses between the output of the motor and the input to the generator in this case. Assume the power is transferred between them via a frictionless rotating shaft. The only losses are within the motor and within the generator themselves.)

(Continuing the hint: Keep in mind that this is not the case where a generator drives a motor. In that case, there could be I2R losses in the cables/wires connecting them. But in this problem, the motor and generator are connected mechanically [not electrically], and I suspect you should take the connection as loss-less.)

## What is motor efficiency?

Motor efficiency is a measure of how well a motor converts electrical energy into mechanical energy. It is typically expressed as a percentage, with higher percentages indicating more efficient motors.

## How is motor efficiency calculated?

Motor efficiency is calculated by dividing the mechanical output power by the electrical input power, and then multiplying by 100 to get a percentage. The mechanical output power is typically measured using a dynamometer, while the electrical input power can be measured using a wattmeter.

## What factors affect motor efficiency?

There are several factors that can affect motor efficiency, including the design of the motor, the quality of the materials used, the operating conditions (such as speed and load), and any external factors like temperature or humidity.

## Why is motor efficiency important?

Motor efficiency is important for several reasons. First, more efficient motors can save energy and reduce operating costs. Second, they can also reduce carbon emissions and contribute to a more sustainable environment. Lastly, higher motor efficiency can also result in increased performance and reliability.

## How can motor efficiency be improved?

Motor efficiency can be improved through various methods, such as using high-quality materials, optimizing the motor design, and implementing advanced control techniques. Regular maintenance and proper operation can also help maintain motor efficiency over time.