Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Chapter 57, Problem 2SQ
To determine
Explain the procedure to obtain the above base speed of a DC motor.
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Give the definition of percentage speed regulation.
: Fill in the blank fields below:
(1) A dc drives are operating in- - quadrants when the supply voltage is- --than the back emf,
and in the --------quadrants when the supply voltage is ---------------than the back emf.
„For a speed less than the base speed, the -----
-are maintained constant at their rated value (2)
.and the---------is varied to control the speed
(3) In a single phase semi-converter dc drives a freewheeling diode is used to ensure-
(4) In a single phase full-converter dc drives, the motor is operating in the 1ª quadrants if the armature
converter firing angle is-----and in the 4 th quadrants if the armature converter firing angle is-------.
(5) In constant power drive, the speed is controlled by
(ii) What is displacement power factor and true power factor?
Describe the significance of these power factors for a
non-liner load like PWM based variable frequency
drives.
Chapter 57 Solutions
Electric Motor Control
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- analyze 3 commonly used ac motor starting methods using suitable diagrams and torque-speed curvesarrow_forward7. The following table relates to the open-circuit curve of a shunt gen- crator running at 750 rev/min: Generated voltage (V) Ficld current (A) 10 172 300 360 385 395 0 1 2 3 4 5 Determine the no-load terminal voltage if the field circuit resistance is 125 N. If the speed is now halved, what is the resultant terminal voltage? At the reduced speed, what value of field circuit resistance will give a no-load terminal voltage of 175 V? (N.C.T.E.C., 0.2)arrow_forwardFrom the curves above find:the stall torque ?? in mN-m, the no-load speed ?max in rpm and the stall current ?? in A for 12V input.what's the corresponding motor model ?Find the equation of current ? (? ) and speed ? (?) in function of torque ?.arrow_forward
- (c) In analyzing load torque of a drive system, several components need to be taken into consideration. State and briefly discuss each component of load torque.arrow_forwardDescribe the merits of buckhholz relayarrow_forwardTwo identical 3-phase, 500-V induction machines are mechanically coupled for a back-to-back test. One machine is motoring from a 500-V, 50-Hz supply and the other is generating on to a 3-phase, 500-V synchronous machine for which the fre- quency can be controlled. It is required to run the motoring induction mạchine at 40 hp. Neglecting the slight change in the generating machine parameters due to oper- ating at a reduced frequency, estimate the rating of the synchronous machine for this duty and the frequency at which it must be run. Line input readings for each machine No load 500 V 8.5 A 1-6 kW Locked rotor 100 V 30 A 1-6 kW Friction and windage loss per machine 0-8 kW. R = R2'arrow_forward
- Q4: Briefly describe how the speed varies as the mechanical load applied to the squirrel-cage induction motor increases, i.e. as the motor torque increases.arrow_forwardA shunt generator on dest is separately encited and driven at 1000 rev /min. The open circuit test chars. are given Field test CA o 0'157 O.477 0 663 O.805 1.0 129 Induced Emf CU) 12a5 300 400 100 450 500 550 ine mlc is then shunt Connected and gun at l000 revlmine with a constant field cicuit esistance of 540R. The agmature docuit resistamee is er. Deduce and plot the load Chargaetesistics of this mle,negleeting effeetof amarterre reaction.what is value of manimum lbud cursrent.arrow_forward3. Find the transfer function, 0,(s)/E,(s), for the motor and load shown in the figure below. The torque-speed curve is given by Tm = -8awm + 200 when the input voltage is 100 volts. edt) Motor | N = 20 N2 = 100 N3= 25 Ja = 1 kg-m? Da = 5 N-m-s/rad DL = 800 N-m-s/rad N4 = 100 J = 400 kg-m²arrow_forward
- Explain the DC Machine losses in briefly.arrow_forward6. The block diagram of a video tape drive is shown in Figure Q.6. It is important for the quality of the video image that the tape spool is rotated at a particular reference speed, m,. The actual speed of the tape, o, is sensed, and fed back, any error, E(s) being passed to the controller, G(s), which controls the torque motor. The tape is also subject to torque disturbance, D(s) due to frictional and other effects. a) It is proposed to use a simple proportional controller. Assuming no change in reference speed, calculate the necessary proportional gain, K„, if the maximum allowable steady state error is 0.01rad/s in response to a step disturbance torque of 1Nm. b) Derivative action is added to the controller. Calculate the necessary proportional and derivative gains K, and K,, if the maximum allowable overshoot in speed is 20%, and the speed must settle to its final value in less than 0.25s in response to a unit step change in reference speed, assuming no disturbance. c) Using the…arrow_forward(ii) Briefly describe the working principle of induction motor speed control for below and above base speed using constant Volts/Hertz (V/f) technique. Torque-speed curve diagram can be used to support the description.arrow_forward
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