This circuit “3 Phase Induction Motor Starter” is one such starter. It is a very low-cost but highly reliable gadget, besides being fool-proof. Of all AC motors available, a polyphase induction motor is one that is mostly used in several kinds of industrial drives. this is because it is simple, extremely rugged, low cost, reliable, high efficient and requires little maintenance.
Among the induction motors available, a squirrel cage machine is the best. However, such an induction motor can never be started by direct switching, as the motor can never be started by direct switching, as the motor would take 7 to 10 times their full-load current and would develop only 1 to 2 times their full-load torque. The initial excessive current is highly objectionable because it produces a large line voltage drop, which affects the operation of other electrical equipment connected to the same lines. So to prevent this, a starter is used.
Circuit Description of Automatic Induction Motor Starter
The circuit “3 Phase Induction Motor Starter” basically consists of a 555 timer chip (IC1). This timer switches on the 3-pole/3-change relay (connected in star mode for starting and delta mode for running) after a delay of about 60 seconds approximately, hence switching on the motor safely and also preventing line voltage drop. Here capacitor C1 starts charging as soon as the power is switched on.
When C1 is charged to 2/3 Vcc the output goes low and energizes the relay which changes the contacts and hence the motor connections. The LED in the 3 Phase induction motor starter is on during the charging period of C1 and acts as a delay indicator. Diodes D2 and D3 protect the circuit against reverse polarities.
Another advantage of the circuit 3 phase induction motor starter is that even in the case of power interruption, the motor would re-start in its usual manner. An automatic induction motor circuit is very simple and can be assembled in less than an hour. Care has to be taken about the high voltage power lines.
PARTS LIST OF 3 PHASE INDUCTION MOTOR STARTER
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Resistor (all ¼-watt, ± 5% Carbon) |
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R1 = 500 KΩ R2 = 10 KΩ R3 = 1 KΩ |
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Capacitors |
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C1 = 67 µF/25V (Electrolytic Capacitor) C2 = 1 µF/25V (Electrolytic Capacitor) C3 = 0.01 µF (Ceramic Disc) |
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Semiconductors |
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IC1 = NE555 (Timer IC) D1, D2, D3 = 1N4007 (Rectifier Diode) LED1 = 5mm Red Color LED |
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Miscellaneous |
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RL1 = 12V-3poles/3change relay SW1 = TPST Switch |
Various other motor driver circuits posted in bestengineeringprojects.com
- Automatic Suction Tank Motor Controller
- DC Motor Control Circuit
- AC Motor Speed Controller Circuit Using AT89C51