The laboratory stand is designed for carrying out laboratory works in universities and secondary technical educational establishments.
Structurally the stand consists of two parts:
- body in which electric equipment is mounted, power module, electric cards, front panel and desktop of integrated table;
- aggregate containing one asynchronous motor with phase-wound rotor, one asynchronous motor with squirrel cage rotor and optical velocity meter.
The bench can be supplemented with electrical machinery unit on the basis of electric motors of 90 W power.
The stand frame contains:
Frequency converter used for alternating current three-phase circuit of regulated frequency and voltage asynchronous motor with squirrel cage rotor. The converter is based on microcontroller MB90F562 (Fujitsu) and intelligent module PS11035 (MITSUBISHI). The controller is used for calculating input (voltage and frequency) and output (power and voltage) signals, arranging data exchange with PC, displaying measured values on the front panel of the stand. Power module includes power circuits of three-phase bridge rectifier and inverter on IGBT transistors, driver and protection circuits (from short circuit currents, insufficient driver voltage and wrong control signals).
Pulse width modulator used for feeding rotor circuit of three-phase asynchronous motor with phase wound rotor in generator mode. Pulse width modulator is designed on the basis of frequency converter. Its two arms are used as irreversible PWMs for rotors of three-phase asynchronous motor. Control module is based on microcontroller AT Mega 163 (Atmel) and is used for calculating input (current) and output (rotor current, rotational frequency of the devices) signals, arranging data exchange with PC, displaying measured values on the front panel of the stand.
Control module is based on digital measuring complex built into the stand and connected to PC through USB port. Laboratory works can be done in both manual and PC interactive modes.
Relay contactor control allows:
- connecting generator in parallel work with circuit ~3 50Hz 220/127 V;
- selective engaging of the branches of double-circuit line between feeding line and synchronous generator;
- changing branch capacity of three phase transmission line;
- establishing short circuit type, varying the time of creating short circuit mode between 1 -10 sec.
- waster energy gate at intelligent module overvoltage;
- incandescent lamps for synchronizing three phase generator with network.
The additional module contains:
- relay subsystem starter;
- resistors and throttles simulating active and inductive transmission line resistances.
The module contains ventilator for cooling ceramic wire resistors. The front panel shows electrical circuits of objects under study. All the circuits shown on the panel are divided into groups according to the subject-matter of works. Patchholes, digital instruments indicators, switching equipment and the controls allowing to alter operating parameters are mounted on the panel.
The front panel controls include:
- assigning potentiometer for controlling irreversible pulse width modulator feeding the rotor of asynchronous motor with phase wound rotor in synchronous machine mode;
- assigning potentiometer of frequency converter allowing to alter output frequency smoothly (0÷89Hz) and output voltage (0÷220V) for feeding the asynchronous motor with squirrel cage rotor;
- relay subsystem controls.
Assemble a circuit of the object under study using unified jumpers allowing to assemble circuits while keeping them in evidence. Laboratory works can be done both manually and in PC interactive mode. There is a possibility to assemble customer’s own circuits using various length jumpers and switching to measurement channels of the microprocessor measuring system MPMS.
Software and user’s manual are supplied with the laboratory stand:
- Program for testing students’ knowledge before conducting the works. Both theoretical knowledge and understanding contents of the laboratory work are tested. Each student’s knowledge level id graded.
- Software for the measuring complex.
- A complete set of methodical and technical documents for teaching staff.