Single Phase Semi Converter Fed DC motor drive

Experiment:Single Phase Semi Converter Fed DC motor drive


Aim: 

To study the operation of Single Phase Controlled DC Drive using Armature Control method.

Learning Objectives:

  • To study speed variations of a DC shunt motor.

  • To study open loop and closed loop controls.

  • To study armature and field control for speed control of DC motor

Apparatus:

  • Experimental kit

  • DSO/CRO (Unearthed)

  • Multimeter

  • Patch cords and DSO probes


Prerequisite Test


Theory:

DC motors:

DC Motors plays an important role in energy conversion process. It is a machine which converts electrical energy into mechanical energy. In mechanical system, speed varies with number of task so speed control is necessary to do mechanical work in a proper way. It makes motor to operate easily. DC motors have been used in industrial applications for years. Coupled with a DC drive, DC motors provide very precise control. DC motors can be used with conveyors, elevators, extruders, marine applications, material handling, paper, plastics, rubber, steel, and textile applications to name a few.

  • Direct current (dc) motors have variable characteristics and are used extensively in variable-speed drives.

  • DC motors can provide a high starting torque and it is also possible to obtain speed control over a wide range.

  • The methods of speed control are normally simpler and less expensive than those of AC drives.

  • DC motors play a significant role in modern industrial drives.


DC motor Drives:

  • Controlled rectifiers provide a variable dc output voltage from a fixed ac voltage, whereas a dc-dc converter can provide a variable dc voltage from a fixed dc voltage.

  • Due to their ability to supply a continuously variable dc voltage, controlled rectifiers and dc-dc converters made a revolution in modern industrial control equipment and variable-speed drives, with power levels ranging from fractional horsepower to several megawatts.

  • Controlled rectifiers are generally used for the speed control of dc motors.

  • The alternative form would be a diode rectifier followed by dc-dc converter.

  • DC drives can be classified, in general, into three types:

1. Single-phase drives

2. Three-phase drives

3. DC-DC converter drives


Block Diagram of Kit



OPEN LOOP DRIVE:

Armature Control:

  1. Switch on power supply.

  2. Connect point ‘A’ to point ‘B’ on panel.

  3. Observe and draw O/P of line sync circuit, Comparator o/p , pulse stuffing and

  4. Output of Pulse transformer between ‘G’ & ‘k’. on DSO with respect to Gnd..

  5. Using the pot set Field voltage = (constant)

  6. Connect DC motor to O/P of Semi converter (Armature of motor).

  7. Vary Armature voltage by using pot provided near to pt. ‘A’ firing angle can be varied & can be measured at the O/P of comparator.

  8. By varying firing angle O/P voltage can be varied and thus speed of motor can be changed

  9. Measure Firing angle, Armature voltage and Speed.

  10. Tabulate the readings.

  11. Draw the Graph of Armature voltage versus Speed on graph paper.

Video


Observation Table

Sr.no.

Toff(time)

Firing angle

Armature Voltage(Va)

Speed(RPM)

































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