What Is a Voltage Transducer?

A voltage sensor is a sensor that can sense the measured voltage and convert it into a usable output signal. In various automatic detection and control systems, it is often necessary to track and collect high-speed changing AC and DC voltage signals, and perform spectrum analysis on more complex voltage waveforms. ^[1]

A voltage sensor is a sensor that can sense the measured voltage and convert it into a usable output signal. In various automatic detection and control systems, it is often necessary to track and collect high-speed changing AC and DC voltage signals, and perform spectrum analysis on more complex voltage waveforms. This type of signal may be a high voltage, high current and other strong current, or it may be a weak current with a poor load capacity or a small amplitude signal. In these cases, it is necessary to use a suitable voltage sensor to collect voltage signals that cannot be directly measured or do not match, so as to obtain standardized, electrically isolated voltage signals.

With the development of more and more new technologies, voltage sensors have been further developed and applied. For example, inverters and rectifiers in drive systems, uninterruptible power supplies, active filters, reactive power compensation, battery charging and discharging, semiconductor protection, drive protection and other equipment or systems use a wide variety of voltage sensors. The function of the voltage sensor is to automatically detect the voltage, so that we can control and display the voltage of the equipment or system, and take automatic protection measures such as overvoltage and undervoltage when necessary.

For AC voltage measurement, a voltage transformer can be used as a sensing element, that is, a voltage transformer is used to reduce the measured voltage to a usable low voltage, and then converted into a DC voltage linearly related to the measured voltage through related circuits Send to the data acquisition system and A / D converter.

When the measured voltage is a DC voltage, a voltage-dividing resistor can be used as a sensing element, and the resistance value connected in parallel across the measured element should be sufficiently large (generally, the power consumption should be less than 1/1000 of the rated power of the measured motor) In order to minimize the influence of the loss caused by the loop current on the measured value,

The function of the voltage sensor is to automatically detect the voltage, so that we can control and display the voltage of the equipment or system, and take automatic protection measures such as overvoltage and undervoltage when necessary. Commonly used voltage sensors can be roughly divided into several main types such as voltage transformers, Hall voltage sensors, and fiber-optic voltage sensors according to their different working mechanisms and applications.

(1) Voltage transformer.

With the increasing power system capacity and the continuous improvement of the grid voltage operation level,

To measure voltage with a voltage sensor, it is generally required that the collected voltage signal is proportional to the measured voltage amount, and the phase angle of the two is exactly the same or the phase difference is extremely small. In addition, the voltage sensor has the following basic requirements.

(1) The voltage sensor connected to the circuit under test shall not substantially affect the amplitude and waveform of the voltage under test.

(2) The voltage waveform obtained by the voltage sensor shall be the same as the measured voltage waveform, and the voltage division ratio shall be independent of the frequency and amplitude of the measured voltage.

(3) The voltage partial pressure ratio has nothing to do with the atmospheric conditions (barometric pressure, air temperature, humidity).

(4) The power consumed by the voltage sensor should be small. Under certain cooling conditions, the temperature rise caused by the electrical energy dissipated by the voltage divider should not cause a change in the voltage divider ratio.

(5) The voltage sensor should not be disturbed by the external electromagnetic field.

In voltage measurement, a suitable voltage sensor should be selected according to the specific situation. The basic principles for selecting a voltage sensor are:

The range of the measured voltage is an important basis for selecting a voltage sensor, so there must be a wide enough voltage measurement range;

It should have a sufficiently wide frequency range and a sufficiently high measurement accuracy;

There is a sufficiently high input impedance. The input resistance of the voltage sensor is the extra load of the circuit under test. In order to reduce the impact of the measurement circuit access on the circuit under test, it is required to have a high input impedance;

It should have high anti-interference ability. The measured voltage often contains some components that do not need to be measured such as noise interference. ^[3]