How to compute for the torque developed in the shaft of the motor?

[detski]

How to compute for the torque developed in the shaft of the motor??

Homework Statement

A DC series motor takes 40 A at 220 V and runs at 800 rpm. If the armature nd field resistnces are 0.2 ohm and 0.1 ohm respectively and the iron and friction losses are 0.5 KW. find the torque developed in the shaft of the motor. What will be the output of the motor?

Homework Equations

The Attempt at a Solution

What i did was:
EC= 220-40(.2+.1)
EC= 208
Power of the armature= (0.2)(40)^2=320
power of the field= (.1)(40)^2=160
Poutput= 8.8K-320-160-.5K
Poutput= 7820
7820=(2*pi*800*Torque)/60
Tout=93.34 Nm

My problem>> I don't know what's next..

Is the Friction & Iron Losses same as the SPL of it?

 

[KataKoniK]

First of all, great job on your calculations so far! To compute for the torque developed in the shaft of the motor, we need to use the equation Torque = Power/Speed. In this case, the power we will be using is the output power, which you have correctly calculated as 7820 watts. The speed is given as 800 rpm, but we need to convert it to radians per second by multiplying it by 2π/60. So, the speed is 83.78 radians per second. Plugging these values into the equation, we get a torque of 93.34 Nm, as you have already calculated.

To answer your question about the friction and iron losses, these are not the same as the SPL (sound pressure level) of the motor. Friction losses refer to the energy lost due to friction between moving parts, while iron losses refer to the energy lost due to magnetic hysteresis and eddy currents in the iron components of the motor. Both of these losses contribute to the overall inefficiency of the motor, but they are not the same as SPL.

To find the output of the motor, we can use the equation Power = Torque x Speed. Plugging in the values we have, we get a power of 7799.6 watts, which is very close to the 7820 watts we calculated earlier. This means that the output of the motor is almost equal to the output power we calculated, which is a good indication of its efficiency.

I hope this helps you with your calculations and understanding of torque and power in a motor. Keep up the good work!

 

[piercas]

The torque developed in the shaft of a motor can be computed using the formula:

Torque = (Power output * 60) / (2 * pi * RPM)

In this case, the power output is 7820 W and the RPM is 800. Therefore, the torque developed in the shaft of the motor is:

Torque = (7820 * 60) / (2 * pi * 800) = 93.34 Nm

To find the output of the motor, you can use the formula:

Output = Power input - Iron losses - Friction losses

In this case, the power input is 220 V * 40 A = 8800 W. Therefore, the output of the motor is:

Output = 8800 - 0.5 KW - (320 + 160) W = 7820 W

The friction and iron losses refer to the losses in the motor due to friction and magnetic hysteresis, respectively. They are not the same as the SPL (sound pressure level) of the motor.