Electric motor test bench
An electric motor test stand is a test stand for reproducible testing of electric motors. In addition to the mechanical design, an electric motor test bench consists of measuring systems , sensors and application software . The bus systems used to control and monitor the test items are included in the test system.
There are different types of test stands: development test stand, endurance test stand, end of line test stand, HiL test stand.
General
Tests of electric motors are usually intended to determine characteristic points or entire characteristic curves. But there are also other tests that characterize the electromagnetic behavior of the test object, such as B. generator measurement, measurement of the cogging torque or the run-out measurement .
Working method
Classic exam
Contains a test setup with load machine, coupling and torque measuring shaft. An externally applied load puts a strain on the engine. With this method, simple parameters can be measured directly and derived values can be calculated. The power consumed can be calculated from the input current and the input voltage. The mechanical output and thus the efficiency can also be determined from the output variables of speed and torque.
- advantages
- Measurement possible for different motor types
- No change to the test algorithm necessary
- After the adaptation, further tests can be carried out easily
- disadvantage
- Modification of the mechanics is necessary for every motor or shaft change
- Systematic errors in the test sequence are possible if the tests are parameterized incorrectly
- Time-consuming adaptation of the test items to the test bench before the test
Parameter identification procedure
Use the inertia of the test object as a load to dynamically run through the characteristic curve.
Testing of electric motors without mechanical coupling and without measuring torque and speed. The test is carried out using the voltage and current clamps. The parameters are determined with the help of mathematical models.
- advantages
- Easy construction
- Fast test procedure
- No adaptation for different motor types necessary
- Only current and voltage are measured
- No measurement of mechanical quantities
- disadvantage
- Model adaptation for different engine types
- No static operation with load possible. Various tests such as validation of a rotor temperature model cannot therefore be carried out.
Other exams
- Noise analysis
A noise analysis is carried out using a suitable excitation function. The test function is selected in such a way that all forces that generate noise are analyzed using a noise sensor. The most common sources of noise are: rolling bearings, commutators and electrical forces.
- Generic measurement
Excited and driven electrical machines induce a voltage. This can be measured on the connection lines of the machine. The following applies: U induced is proportional to the speed and U induced is proportional to the excitation. Information about the quality of the windings and the extent of the excitation over the circumference of the coil is obtained from the course of the induced voltage. The measurement of the induced voltage is a simple method for diagnosing the electromagnetic behavior of the device under test.
- Measurement of the cogging torque
In electrically rotating machines, the number of poles in the rotor multiplied by the number of strands in the stator corresponds to the preferred stable positions in which the rotor moves. The size of the cogging torques is influenced by the structure. Regardless of the type of measurement, the load machine drives the currentless test item. The cogging torque is measured with a torque measuring shaft between the test item and the load machine. The cogging torque can be determined in two different ways. - Measurement of the cogging torque at creep speed - Measurement of the cogging torque with a position control. An active load machine is required for both measurements to drive the test item.
See also
literature
- Prof. Dr.-Ing Klaus Metzger (Ed.): Testing of electric motors , imc Meßsysteme GmbH, 2010, ISBN 978-3-00-027178-6