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Relay Holdover Timer

IP.com Disclosure Number: IPCOM000097991D
Original Publication Date: 1961-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Auch, AG: AUTHOR [+2]

Abstract

So long as the input pulse which energizes the relay is of relatively short duration, the holdover timer provides a standard total duration of relay operation. The total duration is uneffected by repetition of the input pulse. The relay operates as if it had a cam type hold circuit.

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Relay Holdover Timer

So long as the input pulse which energizes the relay is of relatively short duration, the holdover timer provides a standard total duration of relay operation. The total duration is uneffected by repetition of the input pulse. The relay operates as if it had a cam type hold circuit.

The relay includes several contacts not shown, pickup coil P, normally open contact 2, which closes when the relay is energized, and hold coil H, which is polarized oppositely to coil P. Coil H is isolated from ground by normally open contact 2. A positive polarity input pulse energizes coil P by a direct path to ground. The alternate path to ground through coil H, via the holdover circuit, initially maintained open by normally open contact 2, is completed at the instant the relay energizes. This marks the start of the operating duration. The holdover circuit also includes capacitor 4, resistor 5 and diode 6 and controls the end of the operating period. During the remainder of the input pulse, there is some bucking of P by the oppositely polarized coil H, but this is inconsequential. With the relay picked up, capacitor 4 charges quickly to block current flow, and the resistor-diode shunt 5, 6 around H shorts out the positive polarity transient which occurs prior to charging of 4.

When the input pulse terminates, capacitor 4 discharges through coil H to ground in holding relationship. Diode 5 presents a high resistance to the negative polarity pulse flowing out of...