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 |