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:
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To study speed variations of a DC shunt motor.
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To study open loop and closed loop controls.
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To study armature and field control for speed control of DC motor
Apparatus:
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Experimental kit
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DSO/CRO (Unearthed)
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Multimeter
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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.
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Direct current (dc) motors have variable characteristics and are used extensively in variable-speed drives.
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DC motors can provide a high starting torque and it is also possible to obtain speed control over a wide range.
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The methods of speed control are normally simpler and less expensive than those of AC drives.
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DC motors play a significant role in modern industrial drives.
DC motor Drives:
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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.
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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.
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Controlled rectifiers are generally used for the speed control of dc motors.
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The alternative form would be a diode rectifier followed by dc-dc converter.
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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
Experiment Video
Procedure
Armature Control:
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Switch on power supply.
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Connect point ‘A’ to point ‘B’ on panel.
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Observe and draw O/P of line sync circuit, Comparator o/p , pulse stuffing and
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Output of Pulse transformer between ‘G’ & ‘k’. on DSO with respect to Gnd..
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Using the pot set Field voltage = (constant)
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Connect DC motor to O/P of Semi converter (Armature of motor).
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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.
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By varying firing angle O/P voltage can be varied and thus speed of motor can be changed
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Measure Firing angle, Armature voltage and Speed.
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Tabulate the readings.
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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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