Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
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Chapter 15, Problem 4RQ
To determine
The factors which determine the amount of torque developed by a 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.
In 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.
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 current
Chapter 15 Solutions
Electrical Transformers and Rotating Machines
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- A motor develops 189 ft-lb of torque at 1745 RPM. What is the horse-power output of the motor?arrow_forwardName three factors that determine the torque produced by an induction motor.arrow_forwardFor what purpose are synchronous motors used? Explain the V curves of the synchronous motor.arrow_forward
- please answer quickly!!arrow_forwardA motor operating at 3450 rpm and is producing a torque of 33 lb in.what is the output horsepower of the motor?arrow_forwardQUESTION 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…arrow_forward
- A (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_forwardName three factors that determine the amount of voltage induced in the rotor of a wound-rotor motor.arrow_forwardWhat is the minimum pulley diameter for a 1 HP motor running at 1750 RPM?arrow_forward
- Name three factors that determine the amount of torque developed by a wound rotor induction motor.arrow_forwardQ1/ B/ A (220 V) series de motor runs at (400 rpm) and its useful torque is (100 Nm). If its efficiency at this load is (80% ), find the load current.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
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