Single Phase DC Drives MCQ Quiz - Objective Question with Answer for Single Phase DC Drives - Download Free PDF

Explanation:

Step-by-Step Solution:

1. Understanding the Duty Cycle:
   • The duty cycle is the fraction of time the converter conducts during one period. A duty cycle of 0.8 implies that the converter is ON for 80% of the time and OFF for the remaining 20%.
   • The equivalent voltage applied to the armature can be calculated using the duty cycle and battery voltage.
2. Voltage Applied to the Armature:
   • The converter modifies the battery voltage depending on the duty cycle. The applied voltage (V_applied) is given by:
   • V_applied = Duty Cycle × Battery Voltage
   • Substituting the given values:
   • V_applied = 0.8 × 100 V = 80 V
3. Armature Voltage Equation:
   • The voltage applied to the armature is distributed across the armature resistance and the back emf (E_b). The armature voltage equation is:
   • V_applied = E_b + I_a × R_a
   • Where:
     • E_b = Back emf developed across the motor
     • I_a = Armature current (30 A)
     • R_a = Armature resistance (0.6 Ω)
4. Substitute the Known Values:
   • From the equation:
   • 80 V = E_b + (30 A × 0.6 Ω)
   • Simplifying the resistance term:
   • 30 A × 0.6 Ω = 18 V
   • Therefore:
   • 80 V = E_b + 18 V
   • Solve for E_b:
   • E_b = 80 V - 18 V = 62 V

Back emf developed across the coil:

The back emf across the coil is calculated to be 62 V

The given figure represents the Single-phase full converter.

1.) Single-phase full converter

2.) Single-phase dual converter

where, V_o1 and V_o2 are the output of converters 1 and 2 respectively

3.) Three-phase full converter

4.) Three-phase dual converter

where, Vo1 and Vo2 are the output of converters 1 and 2 respectively

The given figure represents the Single-phase full converter.

1.) Single-phase full converter

2.) Single-phase dual converter

where, V_o1 and V_o2 are the output of converters 1 and 2 respectively

3.) Three-phase full converter

4.) Three-phase dual converter

where, Vo1 and Vo2 are the output of converters 1 and 2 respectively

Concept:

The average output dc voltage of a 1ϕ semi-converter is given by:

where, V_m = Maximum value of the source voltage 

α = Firing angle

Calculation:

Given, Vs = 230 V

V_m = √2 (220) V

α = 30° 

Purpose of using Freewheeling Diode:

• The freewheeling diode improves the waveform of the DC load current of rectifier circuits, inverter circuits, and chopper circuits by making it continuous.
• The freewheeling diode protects the SCR from getting damaged by the excessive reverse voltage created by the inductive load.
• The freewheeling diode improves the input power factor of the phase-controlled rectifier.
• It also helps to reduce the ripple components in the output when the load is highly inductive in nature.
• It maintains the average output voltage of the circuit when the load is highly inductive in nature.

Purpose of using Freewheeling Diode:

• The freewheeling diode improves the waveform of the DC load current of rectifier circuits, inverter circuits, and chopper circuits by making it continuous.
• The freewheeling diode protects the SCR from getting damaged by the excessive reverse voltage created by the inductive load.
• The freewheeling diode improves the input power factor of the phase-controlled rectifier.
• It also helps to reduce the ripple components in the output when the load is highly inductive in nature.
• It maintains the average output voltage of the circuit when the load is highly inductive in nature.

The given figure represents the Single-phase full converter.

1.) Single-phase full converter

2.) Single-phase dual converter

where, V_o1 and V_o2 are the output of converters 1 and 2 respectively

3.) Three-phase full converter

4.) Three-phase dual converter

where, Vo1 and Vo2 are the output of converters 1 and 2 respectively

Explanation:

Step-by-Step Solution:

1. Understanding the Duty Cycle:
   • The duty cycle is the fraction of time the converter conducts during one period. A duty cycle of 0.8 implies that the converter is ON for 80% of the time and OFF for the remaining 20%.
   • The equivalent voltage applied to the armature can be calculated using the duty cycle and battery voltage.
2. Voltage Applied to the Armature:
   • The converter modifies the battery voltage depending on the duty cycle. The applied voltage (V_applied) is given by:
   • V_applied = Duty Cycle × Battery Voltage
   • Substituting the given values:
   • V_applied = 0.8 × 100 V = 80 V
3. Armature Voltage Equation:
   • The voltage applied to the armature is distributed across the armature resistance and the back emf (E_b). The armature voltage equation is:
   • V_applied = E_b + I_a × R_a
   • Where:
     • E_b = Back emf developed across the motor
     • I_a = Armature current (30 A)
     • R_a = Armature resistance (0.6 Ω)
4. Substitute the Known Values:
   • From the equation:
   • 80 V = E_b + (30 A × 0.6 Ω)
   • Simplifying the resistance term:
   • 30 A × 0.6 Ω = 18 V
   • Therefore:
   • 80 V = E_b + 18 V
   • Solve for E_b:
   • E_b = 80 V - 18 V = 62 V

Back emf developed across the coil:

The back emf across the coil is calculated to be 62 V

Concept:

The average output dc voltage of a 1ϕ semi-converter is given by:

where, V_m = Maximum value of the source voltage 

α = Firing angle

Calculation:

Given, Vs = 230 V

V_m = √2 (220) V

α = 30° 

Purpose of using Freewheeling Diode:

• The freewheeling diode improves the waveform of the DC load current of rectifier circuits, inverter circuits, and chopper circuits by making it continuous.
• The freewheeling diode protects the SCR from getting damaged by the excessive reverse voltage created by the inductive load.
• The freewheeling diode improves the input power factor of the phase-controlled rectifier.
• It also helps to reduce the ripple components in the output when the load is highly inductive in nature.
• It maintains the average output voltage of the circuit when the load is highly inductive in nature.

The given figure represents the Single-phase full converter.

1.) Single-phase full converter

2.) Single-phase dual converter

where, V_o1 and V_o2 are the output of converters 1 and 2 respectively

3.) Three-phase full converter

4.) Three-phase dual converter

where, Vo1 and Vo2 are the output of converters 1 and 2 respectively

When fed from a fully controlled rectifier a dc motor, driving an active load, can operate in forward motoring and reverse braking mode.

Here for continuous conduction mode, by Kirchoff voltage law, average load current 

The given figure represents the Single-phase full converter.

1.) Single-phase full converter

2.) Single-phase dual converter

where, V_o1 and V_o2 are the output of converters 1 and 2 respectively

3.) Three-phase full converter

4.) Three-phase dual converter

where, Vo1 and Vo2 are the output of converters 1 and 2 respectively

Average output voltage of 1ϕ half controlled rectifier = V_o

V_o = 100.85 V

E_a = 100.85 – 6 × 3 = 82.85 V

E_a = k_bN