Question

ENGR 113 Homework DC Motor Objectives Plot the Torque-Speed curve for a given DC motor given the stall torque and no load speed values Calculate the rotational power for a DC motor given the stall torque and no load speed values Plot the rotational power on a Torque-Speed curve to see the relationship between torque, speed, and power Calculate the maximum efficiency of a DC motor. Calculate the operating point for a DC motor given an equation for the load torque. Equipment and Components Microsoft Excel Introduction Every DC motor has a characteristic Torque-Speed curve and Power-Speed curve. The key parameters and/or equations for a DC motor include: • • Stall Torque (Ts): maximum torque generated by a motor. Occurs when speed (6) is equal to zero. No-Load Speed( ): Maximum speed of a motor when there is no torque (T-0). Rotational power (P.): Rate of doing work. Pror =Tow where T = torque, o = angular velocity IT is measured in oz-in and co is in RPM, then rotation power equation is given by: Pror -0.00074.T. (will be used in this homework assignment) Efficiency: equals power out (mechanical/rotational) divided by power in (electrical) 0.00074.T. efficiency T = torque, angular velocity. Vin supply voltage, I current V . Operating Point: the point where the torque required by the load (Tu) equals the torque of the motor (T) • Procedure: The specifications for the DC motor that will be used in the water pump project are: Current Max. Efficiency Speed @ Max. Efficiency Stall Torque No-load Speed Nominal Supply Voltage 0.35 A 4930 RPM 2.97 oz-in 6200 RPM 12 V

need the answer for the question no. 1

Answer 1

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Answer 2

Question 1

T = mw + b

Given that the Stall Torque is . This is the maximum torque generated by the motor. This occurs when the speed is zero.

So when
w =0,

T=T

Substituting this, we get

T. = mx 0+ b

b=T,

Now the no load speed is . This is the speed when there is no torque.

So when ,
“ო = ო

Substituting this we get

0= mxm + b

m = - wm

m = - wm

Hence we can write

T = mw + b

r- :+T,

So the characteristic Torque – Speed equation is

r- :+T,

In the specification, we can see that

T = 2.97 oz - in

wm = 6200 RPM

So

T = 2.97 T=-6200 6200 +2.97

T = -0.000479w+ 2.97

Question (2)

Speed (RPM) 100 200 300 400 500 600 700 800 900 1000 1100 1200 Torque (oz - in) Power (Watts) 2.97 0 2.9221 0.2162354 2.8742 0.4253816 2.8263 0.6274386 2.7784 0.8224064 2.7305 1.010285 2.6826 1.1910744 2.6347 1.3647746 2.5868 1.5313856 2.5389 1.6909074 2.491 1.84334 2.4431 1.9886834 2.3952 2.1269376 2.3473 2.2581026 2.2994 2.3821784 2.2515 2.499165 2.2036 2.6090624 2.1557 2.7118706 2.1078 2.8075896 2.0599 2.8962194 2012 297776 1300 1400 1500 1600 1700 1800 1900 2000