An Energy-Saving Technique for Studying an Electron Beam Valve Based High-Voltage Inverter Physical Model

Abstract

The schemes of inverters applied in static reactive power compensators (SRPC) are as a rule developed with the use of power semiconductor devices (PSD); however, attempts to develop industry-grade prototypes of high-voltage inverters on the basis of serially produced vacuum-tube devices (VTD) are also made. High-voltage electron beam valves (EBV), which feature—owing to beam recovery at the anode — the minimum possible voltage drop across the anode-cathode section in the conductive state among the VTDs and a high steepness of the impulse front and trailing edges in comparison with PSDs, seem to be promising for such applications.

An EBV was simulated in the EWB circuit engineering computer program environment to determine the minimum permissible load resistance at which the EBV has the maximum electrical efficiency up to 0.99.

To determine whether it is advisable to construct such inverters, it is necessary to conduct not only theoretical, but also experimental investigations on physical models using dedicated test benches. A high-voltage energy-saving bench for testing EBVs operating within the SRPC circuit in an inverter mode has been developed. The bench takes power supply from the 3x380 V, 50 Hz network. The bench comprises a three-phase high-voltage transformer, using which the power supply voltage can be increased to a 40 kV level. This voltage is rectified according to the Larionov bridge scheme, and, owing to an artificial midpoint, the 0 to +20 kV and 0 to -20 kV voltages with the maximum current up to 1 A are obtained. The voltage amplitude can be smoothly varied using a three-phase electromechanical regulator installed in the high-voltage transformer primary winding.

A 50 Hz sine-wave voltage is produced in the inverter mode by means of pulse-width modulation (PWM) with a clock frequency smoothly variable in the 1...3 kHz range and is applied to a water equivalent of load. To increase the bench power level during the test and achieve energy saving, a gating logic device (GLD) was introduced, which allows the EBV control system to operate in an intermittent PWM generation mode. The GLD produces pulses using which three cycles of a 50 Hz sine-wave voltage (with the total duration equal to 60 ms) repeating at approximately 1.2 s intervals are generated.

The use of the GLD producing packs of control pulses makes it possible to study the EBV operation modes on the bench at a short-term power of up to 200 kW in pulse-periodic mode, which is significantly (by 10.20 times) higher than the average power of the bench constant-voltage network power supply source. The GLD output voltage waveforms and the load voltage and current front and trailing edge waveforms are given.