The Rotor Tester RT1(2) is the result of years of experience and application feedback in
the field of manufacturing, testing and maintenance of electric induction motors. Since
many years RM Prüftechnik has been asked for a simple but flexible solution for
checking for damaged or broken bars or end rings of squirrel cage rotors of induction
machines.
For this problem, there exist other designs and solutions but they are either very
complex and not flexible enough.
The goal was the design of a hardware which allows a quick but precise determination
of the kind of damage and its location when the rotor is removed from the stator and
special developed test probes are put on its surface.
Above mentioned damages or quality problems could be voids or blowholes and
partially or completely broken bars or end rings. All these damages lead to less efficient
operation of the motor or to a total malfunction of the drive.
This test solution is based on a special power supply, a display unit and two different
probes: one is called the excitation probe and the other the measuring sensor. The test
system consists of more than one set of probes to cover a wide range of rotor sizes and
slot width´s.
In the tester model RT1(2) with integrated oscilloscope the test results are displayed on
the oscilloscope screen. The tester contains a printer and PC connection.
The tester model RT1A without oscilloscope contains only a digital milli-voltmeter for
indication of the peak amplitude of each bar. For display of the waveforms an external
oscilloscope can be connected to the RT1A.
The physical method is a voltage induction which generates a current through the tested
bar which will be finally reconverted into an output voltage by the sensor. This allows a
step by step testing of the conductivity of each bar of the rotor and therefore precise
fault determination and location. Because of the low voltage levels the method is without
any danger of test piece damage or for the user.
