Direct starting or starting with a soft starter of an asynchronous motor under load

Asynchronous machines with a voltage range of 230/400 V can only be operated in the star on a supply network.

The first experiments perform investigations of the behaviour of an asynchronous motor 230/400 V with direct start and direct rotation in the network. Starting the resistors contradicts the current efficiency guidelines. Thyristor-controlled soft starters have been developed for these motors, which can reduce motor voltage without a loss of power.

Objectives

• Mains feedback with direct start with and without load
• Mains feedback with direct rotation with and without load
• Mechanical load of the driven working machine
• Start with soft starters
• Optimisation of the soft starter
• Measurements are performed by the Machine Test CASSY.

The following parameters are determined:

Load simulation:

• Starting current
• Optimum starting time for automatic star-delta start
• Starting torque
• Tilting torque
• Nominal torque
• Maximum acceleration

Power Analyser Mode:

• Voltage of the three phases at idle with and without soft starter
• Current of the three phases at idle with and without starter

Highlights:

• The measurements are carried out with the CASSY Machine Test.
• All measurement channels are potential-free and can therefore be used freely.
• All measurements can be carried out with or without a computer.
• In order to protect against overheating, the stator windings of the asynchronous motor are equipped with thermal detectors.
• The asynchronous motor has an educationally designed terminal board with the winding configuration 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 configurations there are further extended experiments performed with an asynchronous machine:

• E2.2.4.2 Squirrel cage rotor 230/400 0.3
• E2.5.4.1 Direct start and star-delta start of an asynchronous motor under load
• E2.5.4.3 Starting of large flywheel masses with slip-ring motor
• E2.5.4.4 Operating behaviour of speed-variable asynchronous motors under load

Topics

• Direct start at idle
• Rotation at idle
• Direct start of a lift (constant T~ 1)
• Direct start of a lift with large flywheel mass
• Start with soft starters
• Parametrising the soft starter