Static converter drives with asynchronous machines

The power electronics part of this lab course uses training panels. The electrical machine employed is an industrial machine, whereby its characteristic are evaluated with the machine test system 0.3. Power is supplied to the machine under test via a static converter, which obtains its power from the (three-phase) mains network.

Objectives

• Protective measures and electrical safety
• Set-up of power generating systems according to circuit diagrams
• Putting electrical drives into operation
• Recording of load characteristics with various operating parameters
• Achieving skills in measuring electrical machines
• Start-up with reduced mains voltage
• Automatic speed control for an asynchronous (induction) machine

The equipment is used to carry out experiments on influencing the speed of asynchronous machines (IM) as slip-ring rotors with line-operated power converters. The speed of the IM depends on the stator voltage and the rotor resistance and can be influenced in the experiment via these two variables. In addition to commissioning and parameter setting, the changed behaviour of the machine is examined. For this purpose, load characteristics are recorded and characteristic values determined. With a PID controller, the experimental set-ups can be extended to speed-controlled drives.

Highlights:

• Soft start function via three-phase current controller with thyristor.
• Rotor current control via IGBT transistor.
• The measurements are carried out with the Machine Test CASSY.
• All measuring channels are potential-free and can therefore be used freely.
• All measurements can be carried out with or without a computer.
• To protect against overheating, the stator windings of the slip-ring motor are equipped with temperature detectors.
• The slip-ring motor has a didactic terminal board with the winding diagram printed on it.

All functions of the Machine Test CASSY 0.3 can be operated quickly and directly via the display, the rotary wheel and the buttons on the unit. All settings and measurement results can be saved on the unit and quickly called up again later or simply downloaded.

In addition, the Machine Test CASSY 0.3 is fully controllable in real time via RJ45 Ethernet, W-LAN and USB-C interfaces.

These interfaces can be used by the following software:

• CASSY Lab 2 for drives and energy systems,
• MATLAB® and LabVIEW ™
• Lab Docs Editor Advanced

The following integrated servers are available in the Machine Test CASSY 0.3 for the local media connection of at least four end devices simultaneously.

For more details, see product data 7731900 or 7731901 Machine Test CASSY 0.3

The equipment is equally suitable for pupil and student experiments in the laboratory with low voltage (DC, AC and three-phase current) and - with a mobile trainer - for teacher demonstrations in the classroom or lecture hall. The experiments are carried out according to the manual.

The target group is made up of commercial apprentices and students of electrical machine construction. The course offers experiments at an intermediate level and also allows for the necessary insight into machine behaviour for scientific interpretation at undergraduate level. The media connection makes the experiments suitable for demonstration in the classroom or a lecture hall.

In the following set-ups, there are further experiments with a slip-ring machine:

• E2.4.2.1 Uncontrolled / controlled rectifier circuits
• E2.5.4.3 Starting of large flywheel masses with slip-ring motor

Topics

• Drives using motors with slip-ring motors and three-phase power controllers
• Drives using motors with slip-ring rotors and pulse-controlled rotor impedance