DC Motors and Generators
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each of the black spaces below before clicking
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| 1. A ___motor is a DC motor that has the field wiring connected in parallel with the armature. | shunt
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| The interpoles are connected in series with the _____ windings. | armature
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| 3. ____ motors are used in moderate starting conditions and where constant or adjustable speed is required. | shunt
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| 4. DC shunt motors can develop about ____ % to ____ % of full-load torque upon starting. | 250/300
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| 5. With a(n) ____ shunt field, the speed can be regulated by varying the field current, the armature current, or both. | self-excited
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| 6. A ____ winding is a small series field winding that improves stability of the fields while running with reduced current in the field circuit. | stabilizing field
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| 7. DC compound motors have shared characteristics of series motors and shunt motors. True or False | True
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| 8. DC ___ motors are used mostly for special applications that require constant speed under load and high starting torque. | compound
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| 9. What are the two common DC compound motors? | cumulative compound
differential compound
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| 10. DC permanenet-magnet motors use magnets and coils of wire for the field windings. True or False | False
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| 11. Negative voltage regulation occurs only with ___ generators. | series
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| 12. A DC ___ -wound generator provides a source of positive and zero voltage regulation to the load. | shunt
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| 13. A DC __ operates on the principle that voltage is induced in a coil of wire when the coil is rotated in a magnetic field. | generator
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| 14. When the power is removed, DC ___ motors provide some self-braking and produce relatively high torque at low speeds. | permanent-magnet
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| 15. ___ voltage regulation occurs when the countervoltage at no load is greater than the terminal voltage at full load | Positive
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| 16. When connected to 240V, a DC motor that has a winding resistance fo 3.2 ohms at standstill draws ___ A. | 75
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| 17. The field windings in a ____-wound generator consist of a few turns of low-resistance wire because the large load currentflows through them. | series
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| 18. An external ___ applies mechanaical torque to the armature and series field circuit, which induces voltage and current in the generator. | prime mover
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| 19. In a compound-wound generator, the series field is normally stronger than the shunt field. True or False | False
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| 20. When a DC motor connected to 235V accelerates to a speed that generates a countervoltage of 115 V, the total voltage in the motor is ___V. | 120
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| 21. A motor connected to 280 V has a resistance fo 7 ohmns. When the motor accelerates to full speed, the countervoltage is 245 V; the total voltage in the motor is 35 V and the current drawn is ___ A. | 5.0
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| 22. Connecting voltage directly to the field and armature windings of a DC motor allows the motor to produce higher torque in a smaller frame than with an AC motor. True or False | True
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| 23. Interpoles reduce sparking at the ___ of some DC motors. | brushes
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| 24. A __connects a brush to either the positive or negative terminal of the DC source. | pigtail
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| 25. The function of a(n) ___ is to keep armature windings in the correct polarity to interact with the main fields of a motor. | commutator
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| 26. The ___ rule gives the direction of motion for current-carrying wire interacting with a stationary magnetic field. | right-hand motor
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| 27. The neutral plane is ___ to the field flux when there is no current in the armature. | perpendicular
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| 28. Torque is exerted on the ___ when the plane of the armature loop is parallel to the field, and the armature loop sides are at right angles to the magnetic field. | armature
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| 29. The fields in a DC motor often change in polarity. True or False | False
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| 30. Explain how a DC motor can be reversed. | 1. change the polarity of the armature winding or the field windings.
2. use a reversing motor starter
3. change the polarity of the power source on a permanent magnet DC motor
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| 31. From the illustration, identify the type of generator as compound-wound, series-wound, or shunt-wound | A = shunt parallel
B = compound combination
C = series
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Created by:
JoshHampton