Chapter 3

1. Unlike the DC generator, which has a commutator and brushes, AC power is taken directly from the stator winding of the AC alternator

(page 105). T_ Fclip_image002

2. The stator of a single-phase alternator has one winding (or phase) (page 105). T_ Fclip_image004

3. The changing position of the exciter magnet (as it sweeps by poles of an alternator’s stator) produces the voltage variation of a cycle (page 107).

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4. Frequency of power is expressed in cycles per minute (page 107).

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5. Electrical degrees are used to reference both time (during a cycle) and the location (on a pole) because electric machines have a circular shape (page 109). T_ Fclip_image010

6. A single-phase alternator has one phase; a single-phase motor has a start phase and run phase (page 111). T_ Fclip_image012

7. Electrical degrees and mechanical degrees are the same in a two-pole motor (page 111). T_ Fclip_image014

8. The three windings of a three-phase motor are clip_image016from each other (page 111).

9. TWO phases (start phase and run phase) are symmetrically offset when they are located 90 0 from each other (page 111). T_ Fclip_image018

10. The most efficient torque is produced when the current flow in two windings is offset (degrees in time) the same as the windings are offset (degrees in location) (page 113). T_ Fclip_image020

11. The I-IZ value of an AC induction motor’s power supply determines its approximate RPM (pages 114-115). T_ Fclip_image022

1. Current flow can be out of step (in time) with voltage (page 116).

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2. Inductive reactance is a form of resistance (page 117). T_ Fclip_image004[4]

3. Reactive power always describes the current lagging the voltage (page 117).

clip_image006[4]

4. All current-carrying conductors have a magnetic field around them

(page 117). T_ Fclip_image008[4]

5. The power of a magnetic field clip_image010[4]when current increases (page 117).

a. increases

b. decreases

6. A bucking action between magnetic fields of two AC current-carrying conductors creates resistance to (page 117)

a. voltage.

b. current flow.

7. The bucking action (described in #17) clip_image011as Hz increase (page 117).

a. increases

b. decreases

8. The resistance (caused by inductive reactance) increases with the length of a wire (in a straight line) (page 117). T_ Fclip_image013

9. Impedance is the total resistance of an inductive circuit (page 118).

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10. Power suppliers charge for only the true amperes of a circuit (page 118).

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11. A wattmeter can be used to find true amperes of an inductive circuit

(page 118). T_ Fclip_image019

12. An ammeter can be used to find true amperes of an inductive circuit (page 118). T_ Fclip_image021

13. The power factor that is given on the nameplate of a motor is an accurate value for all conditions (page 121). T_ Fclip_image023

14. TWO problems associated with low power factor are voltage drop and an added penalty cost on the power bill (page 119). T_ Fclip_image025

15. A motor designed for 50 1-IZ will have the same horsepower as 60 Hz if the voltage is decreased proportionately (page 122). T_ Fclip_image027

16. The motor described in “Impedance in a Three-Phase Winding” can be tested using 230 volts DC (pages 122-123). T_ Fclip_image029

17. A capacitor will cause the current to (page 124)

a. lead the voltage.

b. lag the voltage.

2. Oil-filled capacitors lower the two-value capacitor motor’s amperes, also lowering the power bill proportionately (page 126). T_ Fclip_image002[6]

3. An oil-filled capacitor can be in the circuit (page 126)

a. 1 second.

b. 1/2 hour.

c. continuously.

4. The electrolytic capacitor can be in the circuit (page 128)

a. 1 second.

b. 1/2 hour.

c. continuously.

5. The capacitor-start motor starts on two-phase current and operates on single-phase voltage (pages 129-130). T_ Fclip_image004[6]

6. Multiple capacitors in parallel can be used to replace a single capacitor as long as the total mfd is the same (page 132). T_ Fclip_image006[6]

7. Why must capacitors that are connected in series have the same mfd rating (pages 132-133)?

8. An ohmmeter can be used to find a capacitor’s mfd rating (page 134).

clip_image008[6]

9. An ohmmeter is used to determine if a capacitor (page 134)

a. is open.

b. is shorted.

c. has capacitance.

d. all of the above.

10. An electrolytic capacitor never becomes weak (page 134). T_ Fclip_image010[6]

11. The line voltage test can destroy a capacitor, but finds flaws that some electronic instruments miss (page 134). T_ Fclip_image012[4]

12. A motor’s capacitor is selected according to horsepower rating alone

(page 137). T_ Fclip_image014[4]

13. The start winding of a capacitor-start motor is in the circuit (page 136)

a. less than 2 seconds.

b. 5 seconds.

c. continuously.

14. The capacitor-start motor will run at exactly nameplate RPM from no load to full load (pages 137-138). T_ Fclip_image016[4]

1. The primary winding of a single-phase transformer is (page 138)

a. connected to the secondary.

b. linked to the secondary by magnetic lines of force.

c. the load side of the device.

2. The amperes of the primary are determined by the load applied to the secondary (pages 139-140). T_ Fclip_image002[8]

3. A solder gun transformer and the squirrel cage winding of a rotor have similar voltage and ampere values (page 140). T_ Fclip_image004[8]

4. The squirrel cage winding forms poles similar to stator poles (page 144).

clip_image006[8]

5. Power in the squirrel cage winding (page 145)

a. comes directly from the line.

b. flows through the shaft to the bars.

c. is transformed from the stator windings.

6. When the rotor is locked, the rotor Hz is the same as the stator Hz (page 145). T_ Fclip_image008[8]

7. Amperes go down as rotor speed increases (page 145). T_ Fclip_image010[8]

8. The load determines the speed of the squirrel cage induction motor (page 145). T_ Fclip_image012[6]

9. The squirrel cage winding produces no torque at synchronous speed (pages 146-147). T_ Fclip_image014[6]

10. Broken rotor bars decrease a motor’s power (page 148). T_ Fclip_image016[6]

11. Why is current nearly eliminated in a cracked rotor bar (page 148)?

12. A motor that fails from broken rotor bars and/or cracked end rings will look like a motor that had failed from being overloaded (page 148).

clip_image018[4]

13. Misaligned rotor iron will lower the motor’s amperes (page 149).


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