Hardware of PLC based Induction Motor

Published: 22nd October 2011
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The system control is realized and tested for an abrasion rotor motor induction, having the technical requirements. The induction motor makes a dc generator, which gives a changeable load. The power supply of 3-phase is linked to a three-phase key switch and then to a three-phase thermal excess relay, which supplies security against overloads of current. The output of relay is linked to the rectifier, which rectify the three-phase voltage and supplies a dc input to the inverter of IGBT (insulated gate bipolar transistor). Its technical requirements are reviewed. The inverter of IGBT exchanges the dc voltage input to voltage output of three-phase, which is given to the induction motor stator. In another word, the inverter is crossed point to the PLC based controller.

This PLC based controller was executed on a modular system of PLC. The architecture of PLC refers to its internal software and hardware. The system hardware of PLC is planned and developed with the below modules as a microprocessor-based system:
power supply
CPU is central processor unit;
AOM is analog outputs module;
AIM is analog inputs module;
DOM is discrete output module;
DIM is stand for discrete input module.

A speed of sensor is utilized for the feedback of speed, a sensor of current is utilized for the feedback of load current, and a second sensor of current is linked to the stator circuits. Therefore, the two loops of feedback of the system closed-loop are setup with the sensor of load current, the sensor of speed, and the AIM. A tacho-generator is applied for speed sensing. The induction machine makes its shaft mechanically and an output voltage is generated, the magnitude of which is proportional to the rotation speed. The polarity based on the rotation direction. The signal of voltage from the tacho-generator has to equal the specified of voltage range of the AIM is 05 V dc and 200-k internal resistance. Other circuits of PLC external control are designed by a supply low-voltage of 24 V dc.

The system is prepared with start, trip push buttons, and stop, as well as with a selector switch of backward and forward direction for the manual control. All of the components: an three-phase switch of automatic, an single phase switch of automatic, a core switch, an automatic load switch, a three-phase thermal overload relay, signal lamps, push buttons for start, stop, and trip, a selector switch, a selector of speed, a selector of gain, as well as the modules of PLC and the rectifier-inverter are assembled in a control panel.

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