•    The above figure shows, the motor is connected to supply terminals through three terminals L, A, and F available in the starter, it is called as three point starter.

•    In this starter the resister elements are mounted behind an insulating board.

•    The end of the resistor elements meet at the brass studs fixed on the front side of the board.

•    The handle of the starter is fixed to a point so as to be moved over the studs against a spring tension.

•    When the starter handle is moved and makes contact with first stud full voltage is applied to series combination of resistor elements and armature.

•    Therefore a reduced voltage is applied to the armature due to drop in the resistor elements and starting current is limited to safe value.

•    At the same time full voltage is applied across the shunt field and this establishes normal flux.

•    As the starter handle is moved towards right from one stud to next stud the resistor elements are cut out one by one and the voltage applied to armature increases step by step.

•    Finally when all the resistance elements are cut out the handle is in on position and full voltage is applied across the armature terminals.

•    Now the current flowing through the no volt release coil develops an attractive force over the soft iron piece fixed to the starter handle.

•    At normal voltage this attractive force holds the handle in on position against the spring tension at the pivoted end of the handle.

•    When the applied voltage falls below certain value or at the interruption of supply voltage, the attractive force developed at the no volt release coil over the handle may not be sufficient to deep the handle in on position against the spring tension.

•    Therefore the handle flies back to off position immediately and avoids restarting of motor on resumption of supply.

•    If such arrangement is not there in the starter and the handle is on position, on resumption of supply full voltage would be applied to the armature terminals.

•    Also, the voltage release coil is connected in series with the shunt field, the starter handle is released to off position whenever the field circuit be opened.

•    This avoids racing or motor to high speed.

•    The over load relay is connected in series with the armature circuit and carries load current.

•    When motor is over loaded the current through over load relay increases. If this current exceeds a predetermined value, the mmf produced by the over load coil lifts the pivoted iron piece underneath the coil.

•    This iron piece short circuits the no voltage release coil and destroy its attractive force over the handle.

•    Therefore the handle is released to off position.

•    When the handle moved to right and resistance elements are cut out, they are in turn, included in the field circuit.

•    Since the resistance of these elements is very small, inclusion of them in the field circuit does not affect the field current appreciably.

•    Another important point is that the armature and shunt field circuits are closed against each other through the starting resistor element even when the handle is in off position.

•    Therefore the energy stored in magnetic circuit gets dissipated slowly through starting and armature resistances.

•    Thus inductance is avoided.


  1. Very important for engg. Student n also for me,bcoz here this topic is briefly explain as compare to book.THANX Admin

  2. Thanx...... that really helped

  3. thanx.... for the compliments dear friends,keep watch this blog for more related contents....

  4. Its a good and useful information .Thanks for sharing this wonderful post with us



PROJECTS 8086 PIN CONFIGURATION 80X86 PROCESSORS TRANSDUCERS 8086 – ARCHITECTURE Hall-Effect Transducers INTEL 8085 OPTICAL MATERIALS BIPOLAR TRANSISTORS INTEL 8255 Optoelectronic Devices Thermistors thevenin's theorem MAXIMUM MODE CONFIGURATION OF 8086 SYSTEM ASSEMBLY LANGUAGE PROGRAMME OF 80X86 PROCESSORS POWER PLANT ENGINEERING PRIME MOVERS 8279 with 8085 MINIMUM MODE CONFIGURATION OF 8086 SYSTEM MISCELLANEOUS DEVICES MODERN ENGINEERING MATERIALS 8085 Processor- Q and A-1 BASIC CONCEPTS OF FLUID MECHANICS OSCILLATORS 8085 Processor- Q and A-2 Features of 8086 PUMPS AND TURBINES 8031/8051 MICROCONTROLLER Chemfet Transducers DIODES FIRST LAW OF THERMODYNAMICS METHOD OF STATEMENTS 8279 with 8086 HIGH VOLTAGE ENGINEERING OVERVOLATGES AND INSULATION COORDINATION Thermocouples 8251A to 8086 ARCHITECTURE OF 8031/8051 Angle-Beam Transducers DATA TRANSFER INSTRUCTIONS IN 8051/8031 INSTRUCTION SET FOR 8051/8031 INTEL 8279 KEYBOARD AND DISPLAY INTERFACES USING 8279 LOGICAL INSTRUCTIONS FOR 8051/8031 Photonic Transducers TECHNOLOGICAL TIPS THREE POINT STARTER 8257 with 8085 ARITHMETIC INSTRUCTIONS IN 8051/8031 LIGHTNING PHENOMENA Photoelectric Detectors Physical Strain Gage Transducers 8259 PROCESSOR APPLICATIONS OF HALL EFFECT BRANCHING INSTRUCTIONS FOR 8051/8031 CPU OF 8031/8051 Capacitive Transducers DECODER Electromagnetic Transducer Hall voltage INTEL 8051 MICROCONTROLLER INTEL 8251A Insulation Resistance Test PINS AND SIGNALS OF 8031/8051 Physical Transducers Resistive Transducer STARTERS Thermocouple Vacuum Gages USART-INTEL 8251A APPLICATIONs OF 8085 MICROPROCESSOR CAPACITANCE Data Transfer Instructions In 8086 Processors EARTH FAULT RELAY ELECTRIC MOTORS ELECTRICAL AND ELECTRONIC INSTRUMENTS ELECTRICAL BREAKDOWN IN GASES FIELD EFFECT TRANSISTOR (FET) INTEL 8257 IONIZATION AND DECAY PROCESSES Inductive Transducers Microprocessor and Microcontroller OVER CURRENT RELAY OVER CURRENT RELAY TESTING METHODS PhotoConductive Detectors PhotoVoltaic Detectors Registers Of 8051/8031 Microcontroller Testing Methods ADC INTERFACE AMPLIFIERS APPLICATIONS OF 8259 EARTH ELECTRODE RESISTANCE MEASUREMENT TESTING METHODS EARTH FAULT RELAY TESTING METHODS Electricity Ferrodynamic Wattmeter Fiber-Optic Transducers INTERRUPTS Intravascular imaging transducer LIGHTNING ARRESTERS MEASUREMENT SYSTEM Mechanical imaging transducers Mesh Current-2 Millman's Theorem NEGATIVE FEEDBACK Norton's Polarity Test Potentiometric transducers Ratio Test SERIAL DATA COMMUNICATION SFR OF 8051/8031 SOLIDS AND LIQUIDS Speed Control System 8085 Stepper Motor Control System Winding Resistance Test 20 MVA A-to-D A/D ADC ADVANTAGES OF CORONA ALTERNATOR BY POTIER & ASA METHOD ANALOG TO DIGITAL CONVERTER AUXILIARY TRANSFORMER AUXILIARY TRANSFORMER TESTING AUXILIARY TRANSFORMER TESTING METHODS Analog Devices A–D BERNOULLI’S PRINCIPLE BUS BAR BUS BAR TESTING Basic measuring circuits Bernoulli's Equation Bit Manipulation Instruction Buchholz relay test CORONA POWER LOSS CURRENT TRANSFORMER CURRENT TRANSFORMER TESTING Contact resistance test Current to voltage converter DAC INTERFACE Digital Storage Oscilloscope ELPLUS NT-111 EPROM AND STATIC RAM Electrical Machines II- Exp NO.1 Energy Meters FACTORS AFFECTING CORONA FLIP FLOPS Fluid Dynamics and Bernoulli's Equation Fluorescence Chemical Transducers Foil Strain Gages HALL EFFECT HIGH VOLTAGE ENGG HV test HYSTERESIS MOTOR Hall co-efficient Hall voltage and Hall Co-efficient High Voltage Insulator Coating Hot-wire anemometer INSTRUMENT TRANSFORMERS Importance of Hall Effect Insulation resistance check Insulator Coating Knee point Test LEDs Display Driver LM35 Life Gone? METHOD OF STATEMENT FOR TRANSFORMER STABILITY TEST METHODS OF REDUCING CORONA EFFECT Mesh Current Mesh Current-1 Moving Iron Instruments Multiplexing Network Theorems Node Voltage Method On-No Load And On Load Condition POTIER & ASA METHOD POWER TRANSFORMER POWER TRANSFORMER TESTING POWER TRANSFORMER TESTING METHODS Paschen's law Piezoelectric Wave-Propagation Transducers Potential Transformer RADIO INTERFERENCE RECTIFIERS REGULATION OF ALTERNATOR REGULATION OF THREE PHASE ALTERNATOR SOLIDS AND LIQUIDS Classical gas laws Secondary effects Semiconductor strain gages Speaker Driver Strain Gages Streamer theory Superposition Superposition theorem Swinburne’s Test TMOD TRANSFORMER TESTING METHODS Tape Recorder Three-Phase Wattmeter Transformer Tap Changer Transformer Testing Vector group test Virus Activity Voltage Insulator Coating Voltage To Frequency Converter Voltage to current converter What is analog-to-digital conversion Windows work for Nokia excitation current test magnetic balance voltage to frequency converter wiki electronic frequency converter testing voltage with a multimeter 50 hz voltages voltmeter

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