In these experiments, the behaviour of an asynchronous motor is investigated upon direct start-up and star-delta start in the network. The experiments are performed with an asynchronous machine 400/692 V. These can only be operated with the star-delta start directly on a supply network. In Germany, the direct start is only allowed with machines up to 4 kW. The high-efficiency machines and their high switch-on currents of up to 8 times the nominal current put a strain on the supply networks.
Objectives
- Mains feedback with direct start with and without load
- Mechanical load of the driven working machine
- Optimisation of the star-delta start
- Determining the switching time of an automatic star-delta circuit
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Measurements are performed by the Machine Test CASSY.
The loads are simulated by the Machine Test System. The variables of torque, speed, acceleration and current are used for evaluation purposes.
The following parameters are determined:
- Starting current
- Optimum starting time for automatic star-delta start
- Starting torque
- Tilting torque
- Nominal torque
- Maximum acceleration
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.
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.
In the following configurations there are further extended experiments performed with an asynchronous machine:
- E2.2.4.1 Squirrel cage rotor 400/690 0.3
- E2.5.4.2 Direct start or start with a soft starter 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
- Direct start of a fan (quadratic T~ nM2)
- Direct start of a fan with large flywheel mass
- Start with star-delta circuit
- automatic star-delta circuit
