Structurally, the training system consists of two parts:
- case with installed part of electric equipment, electric circuit boards, power module, countertop of integrated desktop;
- two machine units, operating in generator-motor system. Two DC electric motors are the part of the first machine unit. One DC electric motor and one asynchronous electric motor with phase rotor are the part of the second machine unit.
The training system may be completed with electric machine units, based on the electric motor with low (90 W) or high power (0,55 kW).
The case consists of:
1. Frequency converter, which is used to form three-phase AC power line of regulated frequency and power voltage of asynchronous electric motor. The converter consists of the control module and power module.
The control module is based on the microcontroller AT Mega163 (Atmel) and used to count input signals of voltage setting, frequency and current of dynamic braking of asynchronous electric drive, exchange data with PC (RS-485), output of measured values (current, voltage, frequency) on the front panel of the training system.
The power module is based on the power smart module PS11035 (Mitsubishi), consisting of power circuits of three-phase bridge rectifier and three-phase bridge inverter, based on IGBT-transistors, drivers, current measurement, voltage and protection circuits. The smart module provides the protection from short circuit current, insufficient drivers supply voltage, fault injection of the control signals. The smart module control system is based on the microcontroller MB90F562 (Fujitsu).
Frequency converter provides the investigation of asynchronous electric motor in all four quadrants of mechanic characteristic, and realizes the dynamic motor braking with regulated current.
2. Bridge reversible symmetrical width-pulse converter is used for power supply of armature circuit of DC electric motor. The width-pulse converter consists of the control module and power module.
The control module is based on the microcontroller AT Mega163 (Atmel) and used to measure input signal of duty cycle setting, output current value from Hall sensor, organize the data exchange with PC (RS-485), output measured values (current, voltage) on the front panel of the training system.
The power module is based on the smart power module PS11035 (Mitsubishi), consisting of power circuits of three-phase bridge rectifier and three-phase bridge inverter, based on IGBT-transistors, drivers, current measurement, voltage and protection circuits.
The smart module provides the protection from short circuit current, insufficient voltage of drivers supply, incorrect injection of the control signals. The smart module control system is based on the microcontroller MB90F562 (Fujitsu).
The width-impulse converter allows to investigate the DC motor with independent excitation in all four quadrants of the mechanic characteristic, realize the dynamic motor braking with regulated equivalent resistance of dynamic braking.
3. Three-channel width-impulse converter is used to regulate current in excitation windings of DC motors. MOSFET transistors of International Rectifier production are used in power supply circuit. The control system is based on the microcontroller AT Mega163 (Atmel) and measures current in DC motors excitation windings, display the measured parameters on the front panel of the training system, connect to PC.
4. The system of controlling and additional measurements is realized on four modules: the parameters measurement module of “generator-motor” system, speed measurement module and time relay, relay subsystem, the module of digital thermometers:
- The parameters measurement module of the “generator-motor” system is based on the microcontroller AT Mega163 (Atmel) and realizes current measurement and voltage of two DC electric motor armatures of the “generator-motor” system, displays the measured parameters on the front panel, connected to PC.
- The module of speed measurement and time relay is based on the microcontroller AT Mega163 (Atmel) and programmable logic EPM7064S (Altera). The time relay has two independent channels with 25,5 sec delay and 0,1 sec response accuracy. The speed measurement is made on two machine units, using discrete speed optical sensors (determine rotation direction, has shaft position accuracy in 1/440 rev.) and displayed on the front panel in rad/sec. Te speed measurement and time relay module organizes the stopwatch operation, all parameters displaying on the front panel and PC connection.
- The relay subsystem allows to realize relay switch, reverse and braking schematics of electric motors.
- The digital thermometer module is based on the microcontroller AT Mega8 (Atmel) and digital temperature sensors DS1820 (Dallas Semiconductors) and realizes the temperature measurement of DC electric motor and asynchronous electric motor with phase rotor and measurement accuracy 0,1 ˚С. The module displays the temperature value on the front panel of the training system and connected to PC.
5. Closed-circuit system of subordinate regulation is used to study the automated control systems. It realizes the functions of speed and current reversible connection, the function of intensity setting of regulated signal.
The power module includes:
- resistors in armature circuit (two levels);
- resistor of dynamic braking of DC electric motor;
- resistors in rotor circuit of asynchronous electric motor (three levels);
- power switches of relay subsystem;
- energy drop resistors in overvoltage of smart modules.
The electrical schemes of investigated objects are displayed on the front panel. All the schemes, displayed on the panel, are divided into groups according to the theme of conducted laboratory experiments. The switch sockets, digital equipment indicators, switch gear apparatus and controls, allowing to change the elements parameters during laboratory experiment. The control points of input, intermediate and output signals of power converter equipment are located on the front panel.
- the setting signal of reversible width-pulse converter;
- control signals from microcontroller to the smart module drivers in all four lines of reversible width-pulse converter;
- voltage and current at the output of reversible width-pulse converter;
- voltage at the output of frequency converter;
- signals in closed-circuit system of subordinate regulation.
The controls on the front panel:
- setting potentiometer to control reversible width-impulse converter, setting signal of closed-circuit system.
- the controls of operating mode of reversible width-pulse converter: voltage source or equivalent resistance of dynamic braking;
- setting potentiometers of width-pulse converters of power excitation windings of DC electric motors (0 ÷ 600 mA);
- setting potentiometers of frequency converter, allowing to change smoothly the output frequency (0 ÷ 150 Hz), output voltage (0 ÷ 220 V), dynamic braking current of asynchronous electric motor with phase rotor (0 ÷ 7 А);
- stopwatch and two time relay controls;
- relay subsystem controls;
To conduct the laboratory experiment it’s necessary to assemble the schematic of investigated object, using jumpers, which allow to introduce the schematic in visual form.
Laboratory experiment may be conducted in manual mode and in the mode of the dialogue with PC.
- repeat the basic theoretical principles studied in the laboratory work;
- check students’ knowledge before performing the laboratory work (theoretical questions, correct circuit assembly, knowledge of hardware, step by step control of understanding the selection of experimental circuit and measuring instruments for the implementation of specific learning objectives).