Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
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Question
Chapter 15, Problem 9RQ
To determine
The factors which determine the speed regulation of the DC motor.
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Question 2
Beli vifth
Slack side
Motor
(imprut)
Tight side
Beli thickpess\
Centre distance
Figure 2
Figure 2 shows an open flat belt drive connected to a motor and a pulley. The
motor transmits 20 kw to the connect pulley of 450 mm diameter and is rotating
at 850 r/min to a second pulley rotating at 400 r/min. The distance between
pulley centres is approximately 2 m. The belt is 6 mm thick and has a density of
970 kg/m. The maximum stress in the belt is not to exceed 2,7 MPa. The
coefficient of friction for both pulleys is 0,3.
Determine:
2.1. The diameter of the second pulley.
2.2. The length of the belt.
3.3. The width of the belt taking centrifugal tension into account.
For what purpose are synchronous motors used? Explain the V curves of the synchronous motor.
QUESTION 8
Consider the equations of motion of an armature controlled DC motor given by
Jw(t)+bw (t) Ki(t) = -Tfriction - Tload (t)
di (t)
+ Ri (t) + Kw (t) =
Vin (t),
dt
where vin(t) is the input voltage and Tload(t) is the input load torque. The outputs are the armature current i(t) and the motor speed w(t).
The steady-state response of motors are specified by nominal voltage, stall torque, stall current, no load speed, and no load current.
At steady-state operation, the motor equations satisfy
bo) -Ki =-T -T.
fric
load
Ri +Kov_-
55
55
The stall torque is the load torque required stead-state speed of the motor is zero.
The stall current is the armature current when the motor speed is zero.
The no load speed is the speed of motor when the load torque is zero.
The no load current is the current when the load torque is zero.
What is stall torque for this motor in N-m? Keep 3 significant figures, and do not include units. Use Scientific notation.
The constants are given below.
Nominal…
Chapter 15 Solutions
Electrical Transformers and Rotating Machines
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- The reason why the starting torque of a series motor is higher than a shunt motor is because the series motor has O more current flowing through its armature O a stronger net magnetic field around both coils during the inrush of stator currentarrow_forwardName three factors that determine the torque produced by an induction motor.arrow_forwardIn a no-load motor, a constant electromagnetic torque of 5 Nm is generated at t = 0. The engine reached 1800 revs in 4 seconds. Calculate motor inertia ignoring friction.arrow_forward
- As shown in the figure below, this is a speed regulation method for DC separately excited motor. a) What is the speed regulation method? b) What are the characteristics for this speed regulation method? B no Ra le lo R: '3 E R3 Tr. Tarrow_forwardA (21 HP, 3-Phase, 380 volts) motor with an efficiency of 95% is operating at a load factor of 0.63. What is the input current (Amperes) when the power factor is 89%? (1 HP = 0.75 kW)arrow_forwardA 480V, 3-phase, 50Hz 6-pole Induction motor with a rated power of 10KVA. (i) Calculate the synchronous speed in rad/sec (ws) (ii) Determine the rotor speed in rpm, if the % slip is 2.5%arrow_forward
- Name three factors that determine the amount of voltage induced in the rotor of a wound-rotor motor.arrow_forwardQUESTION 1 Consider the equations of motion of an armature controlled DC motor given by Jw(t)+bw (t) Ki (t) = di (l) L + Ri (t) + Kw (t) = -Tfriction - Tload (t) Vin (t), dt where vin(t) is the input voltage and Tload(t) is the input load torque. The outputs are the armature current i(t) and the motor speed w(t). When the input voltage and torque are constant, the transient response of this system has the form of the homogeneous solution. What is the time constant of the transient response? Find the characteristic roots of this system first. Keep 3 significant figures, and do not include units. Use scientific notation. The constants are given below: Nominal voltage, Vin(t) = 17 V Moment of inertia of the rotor, J = 0.02 kg-m² Motor viscous friction constant, b = 0.009 N-m-s Friction torque, Tfric = 0.003 N-m Armature inductance, L = 0.1 H Armature resistance, R = 0.35 Back emf constant and motor torque constant, K = 0.21 N-m/A. **Recall that the time constant (or relaxation time) is…arrow_forward7. Who among the following got a patent for an induction motor in 1888? A. Newton B. Torilcelli C. Nichola Tesla D. Thomas Edisonarrow_forward
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