Electric Motor Control
10th Edition
ISBN: 9781305177611
Author: Herman
Publisher: Cengage
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Chapter 21, Problem 8SQ
What is the sequence of the operations if the limit switches, shown in Figure 21–6, are used. (Limit switches were covered in Unit 13.)
Fig. 21–6 Elementary diagram of the reversing starter shown in Figure 21–1. The
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Q5.B How parallel connected DC-DC converters increase the effective switching
frequency? Show the advantages and limitations in these converters.
Q4. Give the reasons for the following
1. In AC machines drives, the frequency modulation index should be integer
regardless the value of switching frequency.
2. Variable de link voltage is adopted in inverter operating in square wave operation
mode
3. Practical values of switch utilization factor is different from theoretical values
4. In three-phase inverter with my is odd and multiple of 3, the even and tripplen
harmonics are zero.
5. The PSC-PWM is attractive for the modular multilevel converter
Q6.B. Answer the following questions
1. Does the steady state load current in a half bridge inverter has an average value and
what is the adverse effect of the average current component?
2. Can the LPF of single phase bridge inverter based on bipolar PWM be used with
single phase bridge inverter based on unipolar PWM? Explain
Chapter 21 Solutions
Electric Motor Control
Ch. 21 - How is a change in the direction of rotation of a...Ch. 21 - Prob. 2SQCh. 21 - If a reversing control circuit contains...Ch. 21 - How is auxiliary contact interlocking achieved on...Ch. 21 - After the forward coil has been energized, is the...Ch. 21 - If a mechanical interlock is the only means of...Ch. 21 - If pilot lights are to indicate which coil is...Ch. 21 - What is the sequence of the operations if the...Ch. 21 - In place of the push buttons in Figure 214, draw a...Ch. 21 - From the elementary drawing in Figure 2110,...
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- Q3. Answer the following questions T 1. Compared to the bipolar voltage-switching scheme, the unipolar scheme is "effectively" doubling the switching frequency. Explain the statement's meaning and how this effect can be generated. 2. What are the properties of a good power switch, and what are its basic ratings? 3. What are the objectives of any PWM strategy for three-phase inverters? 4. Why is the current control PWM rectifier in the dq rotating reference frame preferred over the abc reference frame? 5. Define the switch utilization factor. Show how this factor can be calculated for different single-phase inverters for square wave operation mode at the maximum rated output.arrow_forwardQ1.B. Explain output control by voltage cancellation in a single-phase inverter. What are the advantages over square wave operation?arrow_forwardQ3.B. What is the problem of three-phase HW rectifier and how can be resolved?arrow_forward
- Q3-consider the unity feedback system shown below: a.Evaluate general formula of ess? b.Calculate the steady state error of the closed loop system due to R(s) unit step input, D(s)=0]? c.Calculate the steady-state response when D(s) and ramp and R(s)=0?arrow_forward- = 400KHZ. Q1. In a Boost converter, L = 25 μH, Vin = 12 V, D = 0.4, P = 25 W, and fs (i) if the output load is changing. Calculate the critical value of the output load P,below which the converter will enter the discontinuous conduction mode of operation. Assume the total turn-on loss is equal to 2 W. (ii) Assuming the input voltage fluctuates from 10 V to 14 V and the output voltage is regulated to 20 V. Calculate the critical value of the inductance L below which this Boost converter will enter the discontinuous conduction mode of operation at P = 5 W. (iii) Draw the waveforms for inductor voltage, inductor current, and the capacitor current for this Boost converter at the output load that causes it to operate at the border of continuous and discontinuous modes. vd tow 77 N₂ AT 22 1-1arrow_forwardDon't use ai to answer I will report you answerarrow_forward
- Answer the following questions: 1- Write radiation resistance (R.) equation for infinitesimal dipole antenna. 2- Write the angle expression form of first null beam width (FNBW) for 2/2 dipole. 3- Define the Directivity of antenna. 4- Write radar cross section equation. 5- Write the input impedance (Z) expression of lossless transmission line.arrow_forwardThe input reactance of an infinitesimal linear dipole of length 1/60 and radius a = x/200 is given by [In(/2a) - 11 X-120- tan(kl/2) Assuming the wire of the dipole is copper with a conductivity of 5.7 × 10'S/m. determine at f = 1 GHz the (a) loss resistance (b) radiation resistance (c) radiation efficiency input impedancearrow_forwardQ4- a) For the block diagram of control system shown below with its unit step response. Determine (K, a,damping ration, Maximum overshoot, Wn, Wd,ẞ, ts, tp, td, tr, and overall transfer function? C(1) ↑ 1.4 1.2 1 0.8 0.6 0.4 0.2 R(s) E(s) K C(s) $(s + α) 0.05 0.1 0.15 0.2 +2% -2%arrow_forward
- Determine the power radiated for the antenna has the following specifications (48 ohm radiation resistance, 2 ohm loss resistance and 50 ohms reactance) connected to generator with 12 V open circuit and internal impedance 50 ohm via à long transmission line with 100 ohm characteristic impedance.arrow_forwardDon't use ai to answer I will report you answerarrow_forwardDon't use ai to answer I will report you answerarrow_forward
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