| 摘要 |
548,946. Converting. ELECTRIC CONSTRUCTION CO., Ltd., and MILNE, J. C. April 25, 1941, No. 5329. [Class 38 (ii)] In an arrangement for connecting a loader resistance X across a D.C. circuit L+, L- in response to rise in circuit voltage, e.g. on regenerative braking in a traction system fed by rectifiers, a mercury arc discharge device A is connected in series with the resistance X across the mains and is rendered conductive by a positive impulse applied to a control grid Gr, the impulse being derived from the circuit of an auxiliary anode T or a separate valve which is rendered conductive by application of positive voltage to its grid Gt when the voltage of the circuit L+, L- increases by a predetermined amount. The circuit voltage is applied to a potentiometer P and a proportion thereof, determined by a tapping p, is applied in opposition to negative bias from an auxiliary rectifier B1 to the grid Gt. The circuit of the anode T, controlled by the grid Gt, is energized from a transformer secondary S1, or, to ensure instantaneous response, from a condenser maintained charged through a rectifier, and includes the primary of a transformer T2 the secondary of which provides the positive impulse which overrides a negative bias provided by a rectifier B2 on the grid Gr. A relay system (not described) is associated with the circuit of the main anode for disconnecting the resistance X by extinguishing the arc when the circuit voltage returns to normal. In a modification, Fig. 2 (not shown), a plurality of loader resistances are connected in parallel through a discharge device having a corresponding number of main. anodes. Specification 502,568 is referred to.
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