Ultra Fast Acting Electronic Circuit Breaker 485t55

ULTRA FAST ACTING ELECTRONIC CIRCUIT BREAKER The project is designed to shut down the power supply when it is overloaded. Conventional circuit breaker like MCB based is on thermal bimetal lever trip mechanism. It is very slow and the trip time is dependent upon the percentage of overload. This project senses the current ing through a series element and the corresponding voltage drop is compared against the preset voltage proportional to the current by a level comparator to generate an output for the load to trip. The concept of electronic circuit breaker came into focus realizing that conventional circuit breakers such as MCBs take longer time to trip. Therefore, for sensitive loads it is very important to activate the tripping mechanism at the shortest possible time, preferably instantaneously. This project is demonstrates fast tripping mechanism as against the slow one like MCB. Electronic circuit breaker is based on the voltage drop across a series element proportional to the load current, typically a low value resistor. This voltage is sensed and rectified to DC which is and then compared with a preset voltage by a level comparator to generate an output that drives a relay through a MOSFET to trip the load. The unit is extremely fast and overcomes the drawback of the thermal type. It uses a microcontroller from 8051 family. Further the project can be enhanced by using a CT for galvanic isolation between mains and control circuit. Power electronic devices such as thyristors / IGBTs can be used for ultra fast operation compared to all the methods. BLOCK DIAGRAM

Hardware Requirements 

8051 series Microcontroller

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Op-amp

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Transformer

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MOSFET

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Diodes

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Capacitors

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Resistors

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LED

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Crystal

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LCD

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Voltage Regulator

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Relay

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Lamps

ELECTRONIC SOFT START FOR 3PH IM

The project is designed to provide a soft and smooth start to a 3 phase induction motor. The three phase induction motor during the initial starting condition draws up much higher current than its capacity and the motor instantly reaches the full speed. This results in a mechanical jerk and high electrical stress on the windings of the motor. Sometimes the windings may get burnt. The induction motor should start smoothly and gradually catch up the speed for a safer operation. This project is designed to give a soft start to the induction motor based on the SCR firing triggered by heavily delayed firing angle during starting and then gradually reducing the delay till it reaches zero voltage triggering. This results in low voltage during start and then gradually to full voltage. Thus the motor starts slowly and then slowly picks up to full speed. This project consists of a six anti-parallel SCRs, two for each phase, the output of which is connected to a set of lamps representing the coils of a 3 phase induction motor. The charging and discharging of capacitors is interfaced to comparators resulting in delayed firing pulses during start and then gradually reducing the delay till the motor runs at full speed. Output from the comparators is fed through opto-isolators to trigger the SCRs. Further the project can be enhanced by using IGBTs in place of SCRs with PWM control to reduce harmonic distortions often encountered in SCR triggering mechanism. BLOCK DIAGRAM

Hardware Requirements 

Op-amps as comparators

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Opto-isolators

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Thyristors

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Transistors

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Regulator

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Diodes

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Transformers

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Resistors

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Capacitors

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LEDs

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Lamps

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Q: What is soft start? A: Gradually increasing the supply voltage to the motor is called soft start

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Q: Why bulb is used instead of motor? A: In order to visualize the soft start it is better to use a bulb.

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Q: What is the rating of motor to be used in this project? A: A 3 phase ¼ HP motor is used in this project.

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Q: Does this project use any microcontroller? A: No it is a non-microcontroller based project