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# ELT111

### test 1

Question | Answer |
---|---|

AC voltages change at regular intervals? | true |

Sine waves are the most common waveforms | True |

AC waveform change in direction | true |

E | True |

dc can be changed into ac but ac can not be turned into dc | False |

The amount of current made during induction is based on what 4 factors? | 1 Speed of rotation 2 Strength of magnetic field 3 Length of conductor 4 Angle of conductor |

Most steam driven turbines use what kind of rotor? | A. Cylindrical |

How is output produced by an alternator controlled? | A rheostat changes the excitation voltage |

One complete wave in a waveform is called? | A cycle |

The time to complete one cycle is called? | A period |

What is the cycles per second called? | Frequency |

What is the frequency of a wave if the period time is 2ms? | 500hrtz |

in a 60hertz waveform what is the period time? | 16.7ms |

a system has a Peak value of 200v what is the RMS voltage and how do you calculate? | peak*.707 200*.707=141.4v rms |

a system has a RMS value of 90v what is the Peak voltage and how do you calculate? | rms*1.414 90*1.414= 127.26 peak |

What is the peak to peak value of a system with 100v peak | 200v peak to peak peak value*2 |

A Waveform has a peak value of 80A What is the average value? | 80*.637=50.96A average |

three phase waveform are how many degrees apart? | 360/3=120 120 degrees |

An alterernator has 3 stator coils in a wye configuration A line current is 10A what is phase current? B Line Voltage is 240 volts what is Phase Voltage? | A in wye amps are the same in phase as in the line 10A B Line= phase*1.73 240/1.73= 138.7V phase |

In A Purely Resistive AC Circuit the Current and the Voltage are in? | In Phase |

A 480v 3 phase delta configuration system has 10 ohms of resistance What is the current in phase? What is the total power used? | 480/10 = 48A 48*480*3= 69120Watts |

Name the 4 effects that increase the resistance in an AC circuit | Histersis Skin effect Eddy currents Diaelectric stress |

An alternator is said to be in sync when? | All of the above alternator frequency = system frequency alternator X = system X |

For revolving field synchronous alternators the term stator winding and ___________ and interchangeable | Field Winding |

Created by:
yo2sls