With the VoltageAnalyzer, all types of high voltages can be measured. The frequency response covers the space from DC up to very high pulse frequencies in the MHz-space, making it ideal for high voltage, surge test, and partial discharge measurements.

With the active probe, voltages and voltage peaks are measured where they occur, e.g., in the electric motor directly at the motor terminal board. These voltage peaks can be caused by an inverter. During a surge test, the peaks can be caused by overshoots of the supply line.

Voltage measurement during surge test and partial discharge

It can happen that the voltage measured internally in the surge tester does not exactly match the voltage at the device under test. This is because the unavoidable line inductances and Capacitances in measurement leads between the measurement leads can alter the voltage waveform of the surge signal on its way to the device under test. The steeper the surge impulse rises, the more pronounced this difference.

To accurately measure, for example, the actual partial discharge inception voltage present at the motor terminal board during a partial discharge test, a measurement via the active probe directly at the terminal board is required.

The VoltageAnalyzer was developed precisely for this purpose: the voltage measurement takes place between the phases where the surge test is also performed.

To be able to Test a three-phase Motor quickly and without time-consuming re-clamping, the VoltageAnalyzer therefore has three measurement Connections. These are connected directly to the terminals U, V, and W of the device under test via the shortest possible measurement leads. The measurement point switch-over between the three measurement Connections is fully automatic in the VoltageAnalyzer and synchronized with the surge test.

Communication with the test device

The VoltageAnalyzer has a communication link to the surge tester. Via this link, it is remotely controlled, and the measured values are transmitted to the surge tester. During the surge test, the VoltageAnalyzer automatically switches to the Connections currently being tested. This remote control is performed by the surge tester.

Measured values

The following voltages are automatically measured by the active probe:

• U_Peak: maximum amplitude
• U_Peak-to-Peak: maximum voltage between the highest positive and negative amplitude
• Rise time in ns

At the frequency converter output, the switching edges are still very close to the optimal rectangular shape. The illustration shows the voltage impulses between two phases at the output terminals of the converter. The voltage impulses, pulse width modulation, and the negative and positive half-wave of the sine are clearly visible.

The voltage level results from the AC supply voltage of the frequency converter. Since every frequency converter first rectifies the input voltage, each converter is equipped with a DC link consisting of capacitors that are charged to the input voltage x √2. For 230 V AC, a value of 320 V DC results, and for 400 V AC, a value of approx. 560 V DC. The illustration shows a level of 315 V DC, which corresponds well with the 230 V AC supply.

The electric motor is connected to the frequency converter via cables.

Cables are not ideal electrical components. They consist of resistances, line inductances, and coupling Capacitances between the conductors. As a result, the ideal rectangular impulse, which is still present at the output of the frequency converter, is significantly distorted on its way to the electric motor.

• Active probe with built-in switch-over between three phases
• Potential-free voltage measurement
• Exact surge test directly on the winding
• Elimination of voltage influence on the measurement lead
• Exact measurement of PD voltages – PDIV, RPDIV, PDEV, RPDEV
• Perfect for standard-compliant measurement according to DIN EN 60034-18-41:2021
• Including determination of pulse rise times
• Determination of voltage peaks caused by frequency converters