Alternators & Generators

Question 1

Define a Generator and provide units of measurement

Answer 1

A rotating electrical machine that converts mechanical energy into electrical energy. Rated in Kilowatts or Megawatts of power that they can deliver at rated voltage and speed without overheating.

Question 2

Define a Dynamo:

Answer 2

A rotating electrical machine that converts mechanical energy into electrical energy OR electrical energy into mechanical energy. An electrical dynamo COULD function as a dc generator or as a dc motor.

Question 3

What is an alternator also called?

Answer 3

A synchronous generator.

Question 4

An alternator creates alternating current when being rotated by a mechanical means. T or F?

Answer 4

True.

Question 5

A motor is a rotating electrical machine that converts electrical energy into mechanical energy. T or F?

Answer 5

True

Question 6

What is the role of the field windings?

Answer 6

To create magnetic flux

Question 7

Where are the armature windings located on a traditional dc dynamo?

Answer 7

On the rotor

Question 8

The field windings of ac AC alternator or synchronous motor may be connected to an external circuit by connecting the coil terminals to what?

Answer 8

Slip Rings - two continuous and insulated rings mounted on shaft. Rotate with the coil and shaft.

Question 9

What are commutators also called?

Answer 9

Split Rings

Question 10

Brushes in an alternator are the electrical connection between the field windings and an external circuit. T or F?

Answer 10

True.

Question 11

Electromagnetic induction is the production of a voltage in a conductor because of relative motion between the conductor and a magnetic field. T or F?

Answer 11

True

Question 12

The usual means of controlling generated voltage is to vary the field intensity by changing the amount if current in the field winding. How is this achieved?

Answer 12

With a variable resistor, aka a Rheostat placed in series with the field winding.

Question 13

Even if there is no field current, the core of a generator will typically remain slightly magnetized. This residual magnetism is due to what?

Answer 13

The retentivity of the core material.

Question 14

Name the four things that affect the amount of voltage produced by electromagnetic induction in a generator.

Answer 14

• the flux density or magnetic field intensity
• the relative speed of the conductor to the field
• the length of conductor exposed to the field (which is effected by the number of turns)
• the angle at which the conductor cuts the lines of force

Question 15

Motor or generators must never be overloaded even for a brief time. T or F?

Answer 15

False. Most motors or generators can be overloaded for a brief time.

Question 16

By increasing the number of armature coils and commutator bars, the generator will produce a smoother output waveform. T or F?

Answer 16

True

Question 17

When the armature loop of an ac generator is at 180 degrees, what is the value of the induced voltage?

Answer 17

The value is zero