Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Chapter 7, Problem 3SQ
What are the advantages of a
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The armature circuit of a free excited direct current motor with a nominal voltage of 600 V is fed from an adjusted direct voltage source. The excitation circuit is also powered from a regulated voltage source. It is used in an application that requires motor speed adjustment. The speed of the motor at the nominal armature voltage was measured as 1600 rpm. All losses of the motor and voltage source and the effect of armature reaction are neglected. It is accepted that the engine is not saturated.Answer the questions below.a) Draw the armature and excitation circuit of the motor and write the formulas for the equivalent circuit.b) If the load moment of the motor at the nominal armature voltage is 420 Nm, then calculate the armature current and the input power of the motor.c) If the armature voltage of the motor is kept constant at 600 V and the excitation current is decreased until the speed reaches 4000 rpm, then calculate the shaft moment. Show this working area on the M = f (W) axis.
Interpret the statement with a mathematical calculation/proof, “The same step angle of
4.5° can be achieved with both the micro-stepping and switched reluctance stepper
motors."
[CO-2, C3]
40 The armature, frame, and core of a 12-V DC
control relay are made of sheet steel. The average
length of the magnetic circuit is 12 cm when the relay
is energized, and the average cross section of the
magnetic circuit is 0.60 cm?. The coil is wound with
250 turns and carries 50 mA. Determine
a. The flux density B in the magnetic circult of the
relay when the coil is energized.
b. The force F exerted on the armature to close it
when the col is energized.
Chapter 7 Solutions
Electric Motor Control
Ch. 7 - What are control relays?Ch. 7 - What are typical uses for control relays?Ch. 7 - What are the advantages of a mechanically held...Ch. 7 - Why are mechanically held relays energy-saving...Ch. 7 - Why does the coil (CR) in Figure 719 drop out when...Ch. 7 - Which device is used to connect the load to the...Ch. 7 - Which device is used to connect the load to the...Ch. 7 - What is optoisolation?Ch. 7 - What type of device is used to suppress voltage...
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- A de machine is controlled by the step-down de-de converter shown below. The armature inductance La =0.2 mH and the armature resistance can be neglected. The armature current is 5A. The Buck converter is operating at the switching frequency is 30 kHz and the duty ratio is 0.8. L₁ + Answer the following questions: 1) Calculate the input voltage (Va) if the output voltage (ea = 200 V). 2) Find the ripple in the armature current (a). 3) Calculate the maximum and minimum values of the armature current (la). 4) Sketch the armature current (ia (t)) and the supply current (id (t)).arrow_forwardWhich of the following is preferred to counter the effect of armature reaction in DC machine? O Use of main pole OUse of interpoles Use of series winding O Shifting of brushesarrow_forwardA d.c. motor connected to a 460-V supply has an armature resistance of 0.15 ohm Calculate:(a) The value of back e.m.f. when the armature current is 120 A.(b) The value of armature current when the back e.m.f. is 447.4 V.arrow_forward
- current - 1=?, and the power factor - cosp =?. 4. An out of balance three phase star connected load has the following complex currents: I₁ = lejº,A, I₂ =le¯6⁰,A and I₁=1e¹j6⁰, A. This load is supplied by a four wire power line from a balance voltage source. Find the r.m.s. value of the neutral current Io =? Wait to tharrow_forwardThe excitation circuit of a free-excited DC motor is a single-phase full- wave uncontrolled rectifier and The armature circuit is fed with a single-phase full-wave controlled rectifier. both rectifiers for AC voltage voltage 220 V(rms) ,is 50 Hz. Excitation O resistance of motor Rf = 100, armature force resistance Ra = 2 0 and motor voltage constant Kv = 0.25 V/(A - r/s). The motor is a fixed 10Nm buy under load a) Draw the driver (converter-motor) power circuit. To rotate with 1200 d/d of the motor, b) Calculate the thyristor assembly. c) When the engine is heavily loaded, with a suitable probability value for supply voltage, armature voltage, armature flow wavelengths draw below. d) Calculate the motor power (total input power). (Note: Va = IaRa + ea, Vf = IfRf, ea = Kv Ifw and Te = Kv Ifla)arrow_forwardDraw the DC Machine and label its parts Example. Armature Winding Stator Pole Shoe/Face Field Winding Brush Armature Core Bearing Shaft Commutatorarrow_forward
- 9-In a the shunt field winding is connected in parallel with the armature winding only. Ish Series . Field EJR Shunt Rsh Rse Field 10-The consist of and 11- E = (V – IaRa ) then N = LOADarrow_forwardA 250 V shunt motor, having an armature resistance of 0.2 ohm draws fromthe mains a current of 50 A on half full load. The speed is to beincreased to twice half full load speed. If the torque of the motor is ofconstant magnitude, determine the percentage change in flux required.[Ans. 52.29] I WANT A DIFFRENT APPROACH (NOT COPY PASTE ON LIBRARY)arrow_forwardA 200V long-shunt generator delivers 100A, has an armature resistance of 0.050, a series field resistance of 0.250 and a shunt field resistance of 2000. If a brush contact drop of 2.5V IS considered, what will be the developed power inside the armature of the machine?arrow_forward
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