Efficiency Calculation of a DC Series Motor | Homework Solution

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In summary, a dc series motor with a full load current of 10 A and a 12 V voltage source has iron, friction, and windage losses that account for 9% of the input power. The field winding resistance is 0.1 ohms and the armature resistance is 0.15 ohms, resulting in a voltage drop of 2 V. After calculating all the losses, the power output is 64.2 watts and the overall efficiency is 53.5%.
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Homework Statement

A dc series motor takes a full load current of 10 A from a 12 V voltage source .The iron,friction and windage losses account to 9% of the input power .the field winding resistance is 0.1 ohms and the armature resistance is 0.15 ohms and the voltage drop is 2 V .Calculate the power output and the overall efficiency ?

Homework Equations


The Attempt at a Solution


Okay so first the I armature =I load=I field =10Amp hence power in= Ia?*Vt =10*12=120 W
The I calculated all the losses p losses (windage) = 0.09*120 = 10.8 Watts ,p losses in the core = Ia^2*r =100*(0.25)=25 Watts
Also the brush losses =Vb*Ia= 2*10 =20 Watts ,therefore p output= 120-10.8-25-20 =64.2 watts and the efficiency is p output/p input =64.2/120 =53.5% .

Okay I just need someone to check if I have done the right thing here please ? Thank u
 
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  • #2
The brush voltage drop of 2 volts is the total for both brushes, is it?
 
  • #3
yes the voltage drop is for both brushes
 

FAQ: Efficiency Calculation of a DC Series Motor | Homework Solution

How do you calculate the efficiency of a DC series motor?

The efficiency of a DC series motor can be calculated by dividing the output power by the input power and multiplying by 100. The output power is equal to the product of the motor speed and torque, while the input power is equal to the product of the supply voltage and armature current. The resulting value is expressed as a percentage, with higher percentages indicating a more efficient motor.

What factors affect the efficiency of a DC series motor?

The efficiency of a DC series motor is affected by several factors, including the design and construction of the motor, the quality of its components, and the operating conditions. Higher quality materials and better design can lead to higher efficiency. Additionally, excessive heat or friction can decrease efficiency, so proper maintenance and lubrication are also important for maintaining efficiency.

Why is efficiency important in DC series motors?

Efficiency is important in DC series motors because it directly affects the performance and cost of the motor. A more efficient motor will require less energy to operate, resulting in lower electricity costs. It also produces less heat, reducing the risk of damage to the motor and improving its lifespan. In addition, a higher efficiency motor can provide better overall performance, such as increased torque and speed.

What is the efficiency range for a typical DC series motor?

The efficiency range for a typical DC series motor can vary, but it is generally between 70-90%. This means that for every 100 units of energy put into the motor, 70-90 units are converted into useful work. The exact efficiency will depend on the specific motor design, operating conditions, and load requirements.

How can efficiency be improved in a DC series motor?

Efficiency in a DC series motor can be improved through various methods, including using higher quality materials and components, optimizing the design of the motor, and implementing proper maintenance and lubrication practices. Additionally, using a motor controller can help regulate the power supply and reduce energy losses. Choosing the right motor for a specific application and operating it within its optimal range can also improve efficiency.

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