The hardware involved in this project is described in the following sections.
1. PIC Microcontroller
For controlling purpose, the PIC Microcontroller 16F877A has been chosen for this experiment because it is cheap, easily available, easy to load program and has less instruction for programming process. The PIC microcontroller 16F877A purchased comes with a Starter Kit set as shown in the figure below. Its specifications are as follow:
· 40-pins
· 35 single-word instructions to be learned
· Operating speed: DC – 20 MHz clock input and DC – 200ns instruction cycle
· Analog Features: 10 bit, 8 channel analog-to-digital converter
· 2 pin outs for PWM
2. Induction Motor
The induction motor used for the experiment is a three-phase induction motor from ABB UK with a frame size of 80B as shown in the figure below. The motor has the following specifications:
· Power: 0.75kW (1Hp)
· Rated Speed: 1410 rpm
· Rated Voltage: 230V
· Rated Torque: 5.08 Nm
· Maximum Torque: 19.812 Nm
· Rated Current: 3.306 A
· Pole: 4
· Moment of Inertia: 0.00156 kgm2Weight: 10.5 kg
· Power: 0.75kW (1Hp)
· Rated Speed: 1410 rpm
· Rated Voltage: 230V
· Rated Torque: 5.08 Nm
· Maximum Torque: 19.812 Nm
· Rated Current: 3.306 A
· Pole: 4
· Moment of Inertia: 0.00156 kgm2Weight: 10.5 kg
3. Three-Phase Inverter
The function of the three-phase inverter is to vary the input voltage into the induction motor based on external signal (0-10V) from the PIC. The three-phase inverter used in this project is TOSHIBA Tosvert VF-S7 series industrial inverter as shown in the figure below.
4. Speed Sensor
In order to construct a close-loop system, speed sensor was used to sense the speed of the induction motor. Signal from the sensor is needed by the PIC as the input signal. The speed sensor for this project is an inductive proximity sensor that is connected to a Guntberg AT100 control unit as shown in the figure below. The Guntberg AT100 will decode the signal from the sensor and then display the speed of the induction motor in rpm.
5. Magnetic Brake
The induction motor is subjected to a loading from a 24V DC magnetic brake as shown in the figure below. The purpose of the magnetic brake is to reduce speed of the induction motor for close-loop system implementation. The magnetic brake has a maximum range of 10 Nm and is connected to a Guntberg AT200 control unit. The AT200 will control the magnitude of loading into the induction motor through the magnetic brake. Figure below shows the Guntberg AT200.
6. Potentiometer
The purpose of potentiometer is to vary the voltage by varying resistance value. For this project, a B5K potentiometer has been selected and it has maximum range of 4.14 kΩ. Figure below shows the potentiometer used for this project.
7. Operational Amplifier 741 (op-amp 741)
The function of the op-amp is to amplify signal (voltage) without changing the natural frequency of the signal. For the project, op-amp is used to amplify the voltage from PIC to the three-phase inverter. Using non-inverting amplifier, the voltage from PIC was amplified from 0-5V to 0-10V. The op-amp that used for this project is shown in the figure below.
