Understanding Motor Controls
4th Edition
ISBN: 9781337798686
Author: Stephen L. Herman
Publisher: Delmar Cengage Learning
expand_more
expand_more
format_list_bulleted
Concept explainers
Videos
Textbook Question
Chapter 4, Problem 15RQ
A three-phase motor nameplate indicates a full load current of 362 amperes. The nameplate indicates that the heaters are to be sized for 125% of motor full load current. Current transformers with a ratio of 600:5 are used to reduce the motor current. Using the chart shown in Figure 4–7B, determine the size of overload heaters needed to protect this motor.
Expert Solution & Answer
Want to see the full answer?
Check out a sample textbook solution
Students have asked these similar questions
In a given DC motor, the output power is 20 HP, and the copper losses are 1.1 KW. If the motor is operating at 87 % efficiency, find the converted power and the rotational losses. Select one:
a. Pconv = 16.05 KW and Prot = 1.13 KW
b. Pconv = 17.15 KW and Prot = 3.11 KW
c. Pconv = 14.92 KW and Prot = 1.35 KW
d. None
Question 2 Calculate the amount of DC current required for the magnetic circuit given below to generate a
flux density of 1.0 T in the airgap. The details are
Number of turns, N = 400
The core is made up of steel, the B-H characteristic has been given below
The magnetic core length, le = 500 mm
The airgap length, Ig = 2 mm
The cross-sectional area of the core, Ag = 100 mm²
Neglect leakage and fringing.
Core
Cross-sectional
i(1)
area
as
Air gap
Magnetic path
length
Figure 1
2.0
1.8
B-H Curves for Various Metals
Steel
1.6
1.4
Magnetic
Saturation
1.2
1.0
0.8
Iron
근 0.4
Air
0.2
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Magnetic Field Strength - H (A/m)
Figure 2
Flux Density - B (T)
The working current has a power of 100 kW and a power factor of 0.50. After a capacitor of 75 KVAR is installed, what does the
power factor become?
A 0.84
B 0.71
C 0.63
D 0.78
E 0.92
Chapter 4 Solutions
Understanding Motor Controls
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.Similar questions
- A 480-volt three-phase load is rated at 34.5 kVA. It is to be supplied with variable three-phase voltage. Because the load is continuous, the transformers ratings are to be increased by 1.25% of the rated load. Three variable autotransformers are used to supply this load. Refer to Table 4-2 and determine the standard size of each transformer that should be used to make this connection.arrow_forwardA large motor has a full load current rating of 425 amperes. Current transformers with a ratio of 600:5 are used to reduce the current to the overload heaters. What should be the full load current rating of the overload heaters?arrow_forwardName three factors that determine the amount of induced voltage.arrow_forward
- Power-consuming devices are wired in _____(series orparallel).arrow_forwardRefer to the transformer shown in Figure 5-13 to answer the following questions. The transformer shown in Figure 5-13 is supplying 325 volt amperes to a load. The primary voltage is 240 volts. What is the primary current? Figure 5-13 Autotransformer practice problems.arrow_forwardIf the load in question 7 is connected in a wye, what would be the line voltage and line current supplying the load?arrow_forward
- Refer to the transformer shown in Figure 5-13 to answer the following questions. What is the turns ratio of the winding between points B and E as compared to the winding between points D and E? Figure 5-13 Autotransformer practice problems.arrow_forwardThe arc length voltage characteristic of a DC arc is given by the equation V=24+4L where 'V' is the arc voltage in volts and L' is the length in mm. The static volt-ampere characteristic of the power source is approximated by a straight line with no load voltage of 80V and the short circuit current of 600A. Then the optimum arc length is (mm).arrow_forwardIf the load in question 7 was supplied by two autotransformers connected in open delta, what would be the minimum standard size transformers that could be used to supply this load?arrow_forward
- A 3 kVA motor operates from a 240 V supply at 50 Hz and has a power factor of 0.6. Determine the active power Select one: 1800 W Non of the Answers 1900 W 2000 Warrow_forwardTwo transformers rated at 100 kVA each are connected in an open-delta connection. What is the total output power that can be supplied by this bank?arrow_forwardHow many transformers are needed to make an open-delta connection?arrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Understanding Motor ControlsMechanical EngineeringISBN:9781337798686Author:Stephen L. HermanPublisher:Delmar Cengage Learning
Electrical Transformers and Rotating MachinesMechanical EngineeringISBN:9781305494817Author:Stephen L. HermanPublisher:Cengage Learning
Refrigeration and Air Conditioning Technology (Mi...Mechanical EngineeringISBN:9781305578296Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill JohnsonPublisher:Cengage Learning
Understanding Motor Controls
Mechanical Engineering
ISBN:9781337798686
Author:Stephen L. Herman
Publisher:Delmar Cengage Learning
Electrical Transformers and Rotating Machines
Mechanical Engineering
ISBN:9781305494817
Author:Stephen L. Herman
Publisher:Cengage Learning
Refrigeration and Air Conditioning Technology (Mi...
Mechanical Engineering
ISBN:9781305578296
Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson
Publisher:Cengage Learning
Mechanical Design (Machine Design) Clutches, Brakes and Flywheels Intro (S20 ME470 Class 15); Author: Professor Ted Diehl;https://www.youtube.com/watch?v=eMvbePrsT34;License: Standard Youtube License