Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
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Question
Chapter 21, Problem 7RQ
To determine
The conductor sizes, overload heater size, fuse size, minimum NEMA and IEC starter sizes, and the upper and lower range of starting current for this motor.
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Chapter 21 Solutions
Electrical Transformers and Rotating Machines
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Similar questions
- A 10 kVA transformer has a primary voltage rating of 240 volts and a secondary voltage rating of 480 volts. The transformer is connected to a circuit protected by a 100 ampere circuit breaker. The secondary is protected by a 25-ampere fuse. Does the primary require separate overcurrent protection?arrow_forwardA 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_forwardIf dual-element time delay fuses are to be used as the short circuit protective device, what size fuses should be used to protect the circuit in question #12? Five 5 HP, three-phase motors with NEMA code B are connected to a 240-volt line. The conductors are copper with type THWN insulation. What size conductor should be used to supply all of these motors?arrow_forward
- A 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_forwardFind the value of the currents I1 and 12. 100 ohm 5V 5V 100 ohm 12 O a. 1=-0.3A, 12=-0.1A O b. 11=0.3A, 12=0.1A Oc. 11=0.05A, 12=0.1A O d. 11=0.1A, 12=0.2Aarrow_forwardFind the currents 11 and 10 in the circuit using current division 2kQ I 6kQ 3kN 12kΩ 9mA 1.arrow_forward
- A shunt generator has a full-load current of 100A at 220V. Stray losses are 1kW and shunt field current is 12 A. The armature resistance including brushes is 0.055 ohms. Calculate the efficiency of the machine.arrow_forwardEx: A single phase 50 KVA transformer has primary voltage of 6600 v and secondary voltage of 254 v and has 32 secondary turns. Calculate the number of primary turns and primary and secondary currents.arrow_forwardAn 8 pole, lap connected armature has 500 conductors and its generated e.m.f is 120V. If the flux per pole is 20 mWb, then the speed of machine is,arrow_forward
- Example 7-3. A 460-V, 25-hp. 60-Hz, four-pole, Y-connected induction motor has the following impedances in ohms per phase referred to the stator circuit: - 0.641n X,-1.106 N R2 - 0.332 N X2 = 0.464 XM - 26.3 N The total rotational losses are 1100 W and are assumed to be constant. The core loss is lumped in with the rotational losses. For a rotor slip of 2.2 percent at the rated voltage and rated frequency, find the motor's (a) Speed (b) Stator current (c) Povwer factor (d) Peony and Pout (e) Tiad and Toad Efficiencyarrow_forwardAn alternator with a line voltage of 2400 V supplies a delta-connected load. The line current supplied to the load is 40 A. Assuming the load is a balanced three-phase load, what is the impedance of each phase?arrow_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_forward
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