Measuring accuracy meets perfection.
The VoltageAnalyzer serves to measure all kinds of high-voltages. The frequency range covers DC voltages up to very high pulse frequencies in the MHz-range.
This it is perfectly suited for high voltage, surge voltage and partial discharge measurements.
The active test probe measures voltages and voltage peaks exactly there, where they appear. This may be e.g. in the motor´s terminal board.
These voltage peaks may be caused by a frequency converter or by harmonics caused by the lead.
Voltage measurement at surge voltage and partial discharge
It happens, that the voltage internally measured by the surge voltage tester does not exactly correspond to the test object´s voltage.
This is due to unavoidable inductances in measuring leads and capacities between themn which influence the surge signal´s voltage course on the way to the test object. This especially occurs the higher the surge impulse rises.
However, to be able to precisely measure the partial discharge inception voltage (PDIV) connected to the motor´s terminal board, a direct measurement at the terminal board with the active test probe is required.
For exact this purpose, the VoltageAnalyzer has been developed! The voltage measurement is carried out between the same phases used for the surge voltage test.
To be able to fastly inspect a three-phase motor without reclamping, the VoltageAnalyzer is equipped with three measuring connections which are directly connected to the test object´s clamps U, V and W via preferably short measuring leads. The switchover between the three measuring connections is performed fully-automatic and simultaneously to the surge voltage test.
Communication with the tester
The VoltageAnalyzer is eqipped with a communication interface to the surge voltage tester. This interface serves to remote-control the tester and to transfer the measuring results to the surge voltage tester.
During the surge voltage test, the VoltageAnalyzer automatically switches to the currectly tested connections. The remote-control is done by the surge voltage tester.
Measured values
The following voltages are automatically measured by the active test probe:
- Upeak , maximum amplitude
- Upeak-peak , maximum voltage between the highest positive and negative amplitude
- Rise time in ns
Based on over 25 years experience, extensive know-how and constant improvements, with the combination MTC2/VoltageAnalyzer you get the perfect "state-of-the art surge voltage tester".
Voltage peaks due to frequency converter operation
At the frequency converter´s output the switching slopes are still very close to the rectangular, optimum shape. The following picture shows the voltage´s pulse course between two phases at the frequency converter´s clamps. The pulses, the pulse width modulation as well as the sine´s negative and positive half wave may easily be detected.
The voltage level results from the frequency converter´s AC- supply voltage. As each frequency converter firstly rectifies the input voltage, each converter is equipped with a DC link, which charges with the input voltage x √2 auflädt. For 230VAC a value of 320 VDC and for 400VAC a value of approx. 560 VDC results. The picture shows a level of 315VDC, which matches well with the 230VAC supply.
The motor is connected with the frequency converter via leads. Leads are no ideal electric components as they consist of resistances, lead inductances and capacities. Due to this, the ideal rectangular pulse, which is still existent at the converter´s output, is strongly distorted on the way to the motor. High voltage peaks arise at the rectangle´s edges. Und dies wird umso schlimmer, je länger die Leitung zum Motor ist. Die nachfolgenden Bilder zeigen dies eindrucksvoll.
Lead 10m length
Lead 20m length
In this example the voltage peaks are almost twice as high as the normal rectangular voltage. In practice, even higher voltage peaks may occur, which will inevitabely destroy the motor in case of an insulation which is not suitable for frequency converters.
The next picure shows a voltage peak in detail.
It is clearly visible, that the voltage peak is almost twice as high as the normal rectangular pulse.
