The training laboratory system is used to study automated electric drive, power converter equipment, electric drives controls and automated control systems.
The training system is the modification of NTC-07.24 “Electric drive” and supplied with the laboratory experiment on the investigation of electric drive, based on DC motor.
Structurally, the training system consists of two parts:
- the case, with installed electric equipment, electric circuit boards, front panel, power module, tabletop of the integrated desktop;
- two machine equipment, operating in the generator-motor system. The first machine equipment consists of two DC electric motors. The second one consists of one DC electric motor and one asynchronous electric motor with phase rotor.
The training system may be complected by electric machine units, based on the electric motors with low (90 W) and high (0,55 kW) power.
The following equipment is located inside:
1. Servo drive is used to investigate the servo drive, based on DC motor. Servo drive may operate in two modes:
- Programming. In this mode, after clicking the “Start”, the servo drive moves, according to the angle, set by the position sensor .
- Tracking. In this mode the servo drive tracks the position sensor. Digital servo drive regulator may operate in two modes: PID-regulator or polynomial regulator. It’s possible to change the coefficients and regulator type from the front panel of the training system.
2. Frequency converter is used to form three-phase AC power system of regulated frequency and voltage supply 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 measure input signals of voltage setting, frequency and current of dynamic braking of asynchronous electric motor, to organize data exchange with PC (RS-485), to output measured values (current, voltage, frequency) on the front panel of the training system.
The power module is based on the power intellectual module PS11035 (Mitsubishi), consisting of power circuits of three phase bridge rectifier and three phase bridge inverter, based on IGBT-transistors, the circuits of drivers, current, voltage measurement and protection. The intellectual module allows to protect from short-circuit current, insufficient voltage of drivers supply, fault control signals injection. The control system of intellectual module is realized on the microcontroller MB90F562 (Fujitsu).
The frequency converter allows to investigate the asynchronous electric motor in all four quadrants of the mechanic characteristic, to realize the dynamic braking of the motor with regulated current.
3. The bridge reversible symmetrical pulse-width converter is used to supply the armature circuit of DC electric motor. The pulse-width converter consists of the control module and power module.
The control module is based on the microcontroller AT Mega163 (Atmel) and is used to measure the input setting signal of duty cycle, output current value from the Hall sensor, to organize data exchange with PC (RS-485), to output the measured values (current, voltage) on the front panel.
The power module is based on the power intellectual module PS11035 (Mitsubishi), consisting of the power circuits of three-phase bridge converter and three-phase bridge inverter, based on IGBT-transistors, the circuits of the drivers, current, voltage measurement and protection. The intellectual module allows to protect from short-circuit current, insufficient voltage of drivers supply, fault control signals injection. The control system of intellectual module is realized on the microcontroller MB90F562 (Fujitsu)>
The pulse-width converter allows to investigate the DC motor with independent excitation in all four quadrants of the mechanic characteristic, to realize the dynamic braking of the motor with regulated equivalent resistance of the dynamic braking.
4. Three channel pulse-width converter is used for current regulation in excitation windings of DC motors. MOSFET transistors of International Rectifier are used in the power circuit. The control system is based on the microcontroller AT Mega163 (Atmel) and realizes current measurement in excitation windings of DC motors, display of measured values on the front panel, connection with PC.
5. The control and additional measurements subsystem is realized on four modules: the parameters measurement module of generator-motor system, speed measurement module and time relay, relay subsystem, digital thermometer module.
- Parameters measurement module of generator-motor system is based on the microcontroller AT Mega163 (Atmel) and realizes current and voltage measurement of two armatures of DC electric motors of generator-motor system, display of the measured values on the front panel, connection with PC.
- The speed and time relay measurement module is based on the microcontroller AT Mega163 (Atmel) and programmable logic EPM7064S (Altera). The time relay has two independent channels with 25,5 sec time-delay and 0,1 sec actuating accuracy. The speed measurement is made on two machine units, using discrete optical speed sensors (determine the rotation direction, have the accuracy of determining the position of the shaft in 1/440 revolution) and displays on the front panel in rad/sec. The speed and time relay measurement module organizes the stopwatch operation, all parameters display on the front panel, connection with PC.
- The relay-subsystem allows to realize the relay schematics of the start, reverse, electric drives braking.
- The digital thermometer module is based on the microcontroller AT Mega8 (Atmel), digital temperature sensors DS1820 (Dallas Semiconductors) and realizes the temperature measurement of DC electric motor and asynchronous electric motor with phase rotor with measurement accuracy 0,1 sec. The module displays the measurement temperature on the front panel and connects to PC.
6. The closed system of subordinate regulation is used to study the automated control systems. It realizes the functions of current, speed back coupling and the function of intensity setting of inject signal.
The power module consists of:
- resistors in armature circuit (two levels);
- resistor of the dynamic braking of DC electric motor;
- resistors in rotor circuit of asynchronous electric motor (three levels);
- power starters of relay subsystem;
- power discharge resistors in overvoltage on the intellectual modules.
On the front panel are displayed the electrical schematics of investigated objects. All schematics, displayed on the panel, are divided on the groups, according to the theme of investigated laboratory experiments. Switch sockets, indicators of digital equipment, switch gear apparatus, controls, allowing to change the elements parameters during laboratory experiment are installed on the panel of the training system. The test points of input, intermediate and output signals of power converter equipment are located on the front panel.
The test points:
- setting signal of reversible pulse-width converter;
- control signals form the microcontroller to the drivers of the intellectual module of all four keys of reversible pulse-width converter;
- voltage and current on the output of reversible pulse-width converter;
- voltage on the output of frequency converter;
- signals in closed system of subordinate regulation.
The controls on the front panel:
- setting potentiometer to control the reversible pulse-width converter, the setting signal of closed system;
- operating mode controls of reversible pulse-width converter: voltage source or equivalent resistance of the dynamic braking;
- setting potentiometers of pulse-width supply converters of excitation windings of DC electric motors (0 ÷ 600 mА);
- setting potentiometers of the frequency converter, allowing to change smoothly the set of output frequency (0 ÷ 150 Hz), output voltage (0 ÷ 220 V), dynamic braking current of asynchronous electric motor with phase rotor (0 ÷ 7 А);
- multifunctional control encoder of servo drive circuit board;
- 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.
The training system is supplied with:
- a set of methodical and technical documentation for teaching staff.
- a software.
The software provides the opportunity to:
- repeat the basic theoretical principles, studied in the laboratory experiment;
- check students’ knowledge before performing the laboratory experiment (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).