EDUTEC   Educatie en Techniek

EEM04/C Recording the Characteristics of Asynchronous Motors with a PC

System Description

This LN training system is based on the use of a 300W three-phase motor with squirrel-cage rotor. Loading on the motor is supplied by a magnetic powder brake which can be controlled either manually from a front panel control or by the ASMA software. Sensors are integrated in the brake for detecting speed and torque, so that these values can either be measured on a multimeter (1V/1000 rpm or 1V/Nm), or displayed on a PC with the ASMA software.

Topics Covered

EEM0401 Starting, speed control and rotation reversing.
EEM0402 Checking the power rating.
EEM0403 Short-circuit / Smooth-start circuit.
EEM0404 Starting characteristics (Star circuit).
EEM0405 Load characteristics (Star circuit).
EEM0406 Load characteristics (Delta circuit).
EEM0407 Reactive power compensation.
EEM0408 Load characteristics in circuits and reactive power compensation.
EEM0409 Steinmetz circuit, Connection and rotation reversing.
EEM0410 Steinmetz circuit, Run-up characteristics.
EEM0411 Steinmetz circuit, Load characteristics.

Computer Connection

The AMA software provides online measurement of the characteristics of asynchronous machines. The measured values can be displayed as a chart, digital values or as a table. Operation follows the familiar Windows® techniques with mouse support. A ramp can be defined for recording the measurements, which is applied to control the magnetic powder brake so that the motor is continuously braked down to standstill. The following values can be accessed and displayed:
speed/torque characteristic  excitation and armature current curves  excitation and armature voltage curves  electrical power, mechanical power, efficiency, cos phi, reactive power, apparent power, slip

The LN PC/I1 is used as an interface, which has an integrated microprocessor (type Motorola 68000). A4-channel isolating amplifier is used for galvanic isolation of the machine voltages and currents, connected between PC/I1 and oscilloscope.