WorksheetsElectrical Engineering Quiz
Total questions: 55
Worksheet time: 28mins
If line voltage is 120 V, what is the voltage of each connection?
120 V
208 V
69 V
220 V
Power factor correction can result in which of the following?
Increase in transformer losses
Decrease in transformer capacity
Decrease in losses and increase system capacity
Increase in line losses
Name the power factor correction device most typical when phase shift by a general reactive is to be made.
Synchronous motor
Series reactor
Shunt capacitor
Grid feeder
An alternating current generated through four square phases is fed to the voltage of 400 V/50 Hz. The line to neutral voltage would be:
230 V
400 V
346 V
120 V
Choose the right kVA bank rated for a 500 kW load and 0.8 PF to obtain a 0.95 PF (UPF).
164 kVA
156 kVA
120 kVA
200 kVA
In the context of power, what is a lower power system in practice an actual test for?
Power quality margin.
Power quality voltage.
Power quality people.
Power quality current.
What is S = 1?
S = 1
S = 2
S = 0
S = -1
Which of the following equations describes phase reactive power in an unbalanced three-phase load?
(Iphase) × (Vphase) × cos theta
(Iphase) × (Vphase) × sin theta
(Iline) × (Vline) × sin theta
(Iline) × (Vphase) × cos theta
In a three phase system voltages are separated by:
90°
60°
120°
180°
A resistor has a value of 14 ohms. The current through this resistor is 1.5 Amps. What is the volt drop across the resistor?
14 Volts
21 Volts
1.5 Volts
28 Volts
A wye connected load draws 10A per phase. What is the line current?
5A
7A
10A
17A
Three 35 ohm resistors are connected in delta across a 240 Volt 60 Hz three-phase supply. The line current is:
2.4 Amps
4.8 Amps
11.9 Amps
7.2 Amps
If the phase voltage is 120V, what is the line voltage for a wye connection?
120V
150V
208V
240V
To determine the total true power of a balanced three phase system this equation can be used:
I line × V phase × √3 × pf
I line × V line × √3 × pf
I phase × V phase × pf
I line × V line × pf
When power factor correction capacitors are disconnected from the voltage supply:
They must be immediately reconnected
No special procedures are required
The system must be shut down
Appropriate codes for discharge resistors must be enforced
In an unbalanced three-phase delta connected system, the line voltage is:
the same as the phase voltage
twice the phase voltage
half the phase voltage
three times the phase voltage
When three equal loads are connected in wye and then reconnected in delta, the power of the three loads would be:
2 times greater
1.5 times greater
3 times greater
The same
Power factor correction is used to:
To reduce line loss and increase system capacity.
To increase line loss and decrease system capacity.
To reduce voltage and increase current.
To increase power loss and reduce efficiency.
The ratio between the peak value and the root mean square value (RMS) of a periodic waveform is known as:
Form factor
Crest factor
Power factor
Phase factor
An alternator has a phase voltage of 480V. Determine the line voltage when the windings are connected in delta.
277V
415V
240V
480V
When adding capacitors to a circuit to correct the overall power factor, the capacitors must be connected in:
parallel with the load.
series with the load.
series with the supply.
parallel with the supply.
Adding capacitors to a circuit to correct the overall power factor to unity will cause:
The line current to be reduced.
The line current to be increased.
The voltage to be reduced.
The power factor to decrease.
A three phase motor is connected in wye for starting and then delta for running. The line current when the motor is connected in delta is:
The same as in wye connection
Three times that of the wye connection
Three times less of what it would be in wye connection
Half of the wye connection
A delta-connected alternator has a rated voltage of 240 Volts per phase. The alternator is supplying a load of three 24 ohm resistors connected in wye. Calculate the line voltage.
120 Volts
208 Volts
415 Volts
240 Volts
The purple arrow points to the:
Voltage connection
Neutral connection
Current connection
Ground connection
Adding capacitors to a circuit to correct the overall power factor closer to one will cause the:
Current supplied to the load are increased.
Voltage supplied to the load is increased.
VARS supplied to the load are increased.
VARS supplied to the circuit to be reduced.
Choose the equation that is best suited for a delta connected load that draws a line current of 37A.
37A × √3
37A / √3
37A × 3
37A / 3
An unbalanced wye connected three-phase four-wire system has a line to line voltage of 600 Volts. The line to neutral voltage would be:
600 Volts
208 Volts
347 Volts
120 Volts
Comparing phase power to total power of a three phase wye-connected balanced load:
Phase power is equal to the total power
Phase power is half of the total power
Phase power is double the total power
Phase power is only one third of the total power
In a Wye connected system, the phase voltage is equal to:
VL / 1.732
VL × 1.732
VL / 2
VL
An unbalanced wye connected three-phase four-wire system has a line to line voltage of 480 Volts. The line to neutral voltage would be:
480 Volts
240 Volts
277 Volts
120 Volts
What material is commonly used for the stator core in a three-phase induction motor?
Copper
Aluminum
Laminated silicon steel
Plastic
When would you typically use a delta connection for a motor?
For low voltage requirements
For high torque requirements
For low power factor
For energy saving
How does a rotary phase converter typically generate the third phase?
By using a transformer
By using a rotating motor
By using a capacitor bank
By using a rectifier
The phase sequence in a three-phase induction motor affects which of the following?
The voltage rating of the motor
The direction of motor rotation
The efficiency of the motor
The size of the stator core
An unbalanced wye connected three-phase four-wire system has a line to line voltage of 480 Volts. The line to neutral voltage would be:
208 Volts
240 Volts
277 Volts
480 Volts
A wye connected load draws 10A per phase. What is the line current?
5A
15A
10A
20A
Adding capacitors to a circuit to correct the overall power factor to unity will cause:
The line current to be reduced.
The line current to be increased.
The voltage to be reduced.
The power factor to decrease.
In a Wye connected system, the phase voltage is equal to:
VL / 1.732
VL × 1.732
VL / 2
VL × 2
Comparing phase power to total power of a three phase wye-connected balanced load:
Phase power is equal to the total power
Phase power is half of the total power
Phase power is double the total power
Phase power is only one third of the total power
An unbalanced wye connected three-phase four-wire system has a line to line voltage of 600 Volts. The line to neutral voltage would be:
208 Volts
480 Volts
347 Volts
600 Volts
When adding capacitors to a circuit to correct the overall power factor, the capacitors must be connected in:
parallel with the load.
series with the load.
series with the source.
parallel with the source.
Which of the following equations describes phase reactive power in an unbalanced three-phase load?
I(phase) × V(phase) × sin theta
I(line) × V(line) × sin theta
I(phase) × V(phase) × cos theta
I(line) × V(phase) × sin theta
A delta-connected alternator has a rated voltage of 240 Volts per phase. The alternator is supplying a load of three 24 ohm resistors connected in wye. Calculate the line voltage.
120 Volts
208 Volts
240 Volts
480 Volts
Three 120V single-phase loads are fed from a 120/208V 3-phase panel, they draw different currents. The neutral conductor serves the function of:
Balancing the system
Increasing the voltage
Reducing the current
Providing ground fault protection
Three 35 ohm resistors are connected in delta across a 240 Volt 60 Hz three-phase supply. The line current is:
5.25 Amps
7.62 Amps
11.9 Amps
15.3 Amps
In an unbalanced three-phase delta connected system, the line voltage is:
the same as the phase voltage
1.732 times the phase voltage
half the phase voltage
double the phase voltage
Adding capacitors to a circuit to correct the overall power factor closer to one will cause the:
Current supplied to the circuit to increase.
Voltage supplied to the circuit to be reduced.
Power supplied to the circuit to be increased.
VARS supplied to the circuit to be reduced.
In a three phase system voltages are separated by:
60°
90°
120°
180°
A three phase motor is connected in wye for starting and then delta for running. The line current when the motor is connected in delta is:
The same as that of the wye connection
Three times that of the wye connection
Half that of the wye connection
Three times that of the wye connection
When power factor correction capacitors are disconnected from the voltage supply:
No special precautions are needed
Only licensed electricians may perform the disconnection
The supply voltage must be reduced
Appropriate codes for discharge resistors must be enforced
An alternator has a phase voltage of 480V. Determine the line voltage when the windings are connected in delta?
480V / √3
240V
480V × √3
480V
A resistor has a value of 14 ohms. The current through this resistor is 1.5 Amps. What is the volt drop across the resistor?
10 Volts
21 Volts
28 Volts
14 Volts
Power factor correction is used to
To reduce line loss and increase system capacity.
To increase resistance in the circuit.
To decrease voltage.
To increase current.
If the phase voltage is 120V, what is the line voltage for a wye connection?
100V
150V
208V
120V
