Application Cases

Experiment Name: Observation of Metal Particle Discharge

Test Equipment: High-voltage amplifier, Signal generator, High-speed camera, etc.

Experimental Process:

Figure 1: Schematic diagram of the experimental platform

The experimental setup is shown in Figure 1. To facilitate the collection of metal particles moving beyond the electrode range, the electrodes were suspended in an acrylic funnel-shaped cavity using plastic bolts, with a particle collection cylinder placed at the bottom. The electrode spacing was set to 2 cm, and experiments were conducted in air. A positive DC voltage signal generated by the signal generator was amplified by the high-voltage amplifier and applied to the electrode plates. A high-speed camera was used to observe the motion and breakdown of metal particles. During particle motion observation, a strong LED light was used to supplement the illumination for the high-speed camera. When capturing arc discharge images in the air gap, a blackout cloth was attached to the outer surface of the cavity for shading.

Experimental Results:

Figure 2: Motion images of aluminum spheres (r = 1 mm)

Aluminum spheres with radii of 0.5 mm, 1 mm, and 1.5 mm were used to verify the particle lift-off voltage. A stepwise voltage increase method was applied using a function signal generator. Under supplementary illumination from a strong LED, the lift-off and motion images of the particles were captured with a high-speed camera (as shown in Figure 2), and the lift-off voltage values were recorded. The experimental results were found to be largely consistent with the theoretical calculations. Observations from the high-speed camera revealed that an aluminum sphere with r = 1 mm completed one motion cycle (from the lower electrode to the upper electrode and back to the lower electrode) in an electrode gap of d = 2 cm, taking approximately 80 ms.

Figure 3: Breakdown images of copper spheres (r = 1.5 mm)

Under shaded conditions, experiments were conducted with 1.5 mm copper spheres. The voltage was gradually increased, but the particles did not lift off until breakdown occurred, indicating a static direct breakdown. The breakdown arc originated from the top of the particle, perpendicular to the upper electrode, as shown in Figure 3.

Figure 4: Breakdown images of aluminum spheres (r = 1 mm)

Experiments were conducted with 0.5 mm, 1 mm, and 1.5 mm aluminum spheres and 0.5 mm copper spheres. The voltage was gradually increased, and the following observations were made: after reaching the lift-off voltage, the particles lifted off and moved reciprocally between the two electrodes. When the voltage was further increased until gap breakdown occurred, the breakdown arc captured under shaded conditions is shown in Figure 4. The arc extinguished in approximately 0.8 ms, which is very short compared to the 80 ms motion cycle of the metal particles. Therefore, the position of the particles can be considered unchanged during the entire arc discharge process.

Figure 5: Breakdown images of copper spheres (r = 1 mm)

Experiments were conducted with 1 mm copper spheres. The voltage was gradually increased, and the particles lifted off. When the particles first approached the upper electrode, gap breakdown occurred. The captured breakdown process is shown in Figure 5. Multiple experiments revealed that for 1 mm copper spheres, breakdown only occurred when the particles were near the upper electrode, which is consistent with the analysis of the third type of breakdown location in the model discussed in this paper.

High-Voltage Amplifier Recommendation: ATA-7050

Figure: ATA-7050 High-Voltage Amplifier Specifications

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