Roy Hali reveals how Hioki’s new High Voltage Divider VT1005 is providing accurate high voltage power measurement for high frequency applications
Hioki’s new High Voltage Divider VT1005 is an important addition to the company’s power measurement solutions. In combination with one of Hioki’s Power Analysers, the VT1005 enables users to accurately measure power up to 5kV, delivering a significant improvement in accuracy for high frequency applications such as SiC-based solutions or loss measurement of HV coils and transformers.
Alongside the ongoing electrification of our society, there is a rapidly growing need for more electrical power. One of the ways to meet this demand is to increase the system voltage. Obvious applications are ultra-high-speed chargers for electric vehicles (EVs) and solid-state transformers that help to increase the flexibility and reduce the losses of the power grid. For the development of these high voltage systems, accurate power measurement is essential.
A high accuracy power analyser like the Hioki PW8001 can measure power up to a voltage of 1500V. In combination with the VT1005 High Voltage Divider, engineers have the solution for accurate voltage and power measurements from 1500V up to 5kVrms. To guarantee such accurate power measurement results, a HV divider needs to have two main features: high noise resistivity and excellent frequency flatness.
High Noise Resistivity
The VT1005 is highly resistant to both common-mode and high-frequency noise, allowing it to measure voltage accurately even in noisy environments. Since conversion devices like inverters are sources of noise, this level of noise resistance is important to ensure accurate efficiency evaluation.
SiC power devices are characterised by a fast voltage response, and their output waveforms contain numerous high-frequency components. If you check the output voltage of SiC power devices, the VT1005 shows no ringing effect and ensures accurate power measurement.
Frequency Flatness
Frequency flatness defines the gain and phase error of a power measurement system over a defined frequency range. As the VT1005 High Voltage Divider and the current sensors are developed and produced by Hioki, these devices are optimised for the Hioki Power Analysers and offer outstanding performance both in gain and phase accuracy over the entire frequency measurement band.
To further increase the efficiency of high power systems, SiC semiconductors have become popular switching devices. As the switching frequency of SiC semiconductors is 50kHz or higher, power needs to be measured accurately over a broad frequency spectrum, from DC to several hundred kHz. This can become a challenge because not only do voltage and current need to be measured accurately at high frequencies, but the phase angle as well. If your power measurement system does not have a sufficient frequency flatness it could happen that the system efficiency measured exceeds 100%.
Hioki power measurement systems, including HV Dividers and Current Sensors, offer excellent frequency flatness that ensure accurate measurements. To guarantee this at higher voltages, the VT1005 High Voltage Divider delivers a gain error of just ±0.1% up to 200 kHz, and a phase error of just ±0.1° up to 500 kHz (after phase correction by the power analyser).
Loss Measurement Of HF Reactors And Transformers
Hioki provides a solution to measure loss of high voltage HF reactors and transformers used in inverter drives and solid-state transformers. Both the noise resistivity and the frequency flatness make the combination of the VT1005 High Voltage Divider, PW8001 Power Analyser, and the CT6904A Current Sensor ideal for these applications. With this setup, accurate loss measurements can be guaranteed even at a frequency of 300kHz.
Roy Hali is the head of product management at Hioki Europe
