| 摘要 |
<p>The LV unit (1) supplies (4) the HV applicator (5) at variable voltage and frequency. The electrode (9) derives its HV supply from a step-up transformer (7) and voltage multiplier (8). A signal representing HV current(IHT) produces, across a measurement resistance (12) with capacitor filter (13) and peak-looper (14), dual inputs to a calculating unit (20), via a measuring circuit, and via a differentiator (17). At switch-on, current rises rapidly, overshooting before settling at the pre-set level. Too near approach of the earthed work-piece causes dangerous current rises. The calculator initiates alarm (21) and shut-down (22) if a set value, exceeding the permitted overshoot, is attained. The derivative w.r.t. time of the current, monitored at each switch-on, confirms the integrity of the detecting loop; its unsatisfactory behaviour also initiates shut-down.</p> |
