MIL-DTL-19648 Relays, Time Delay, Thermal, General Specification ForThis specification covers the general requirements for thermal, time delay relays for use in electrical applications. Relays covered by this specification are capable of meeting the electrical and environmental requirements when mounted directly to the structure of aircraft, missile, spacecraft, ship, and other primary vehicles or in ground support and shipboard equipment. Other ratings may be as specified \(see 3.1\).

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MIL-DTL-19648E

automatically and instantly at the end of normal operate time by means of a high-speed magnetic-relay,

operated by the thermal relay under test. The time interval shall be measured from this cut-off point until

NO contacts reopen or NC contacts reclose (see figure 2.).

4.7.3.4.2 Saturate release time (SRT) (see 6.7.8). When specified (see 3.1), the saturate release time

shall be measured using generally the same equipment as for normal operate time. The relay shall be

saturated at rated heater power for 15 times normal operate time plus 5 minutes before power is cut off.

The time interval shall be measured from cut-off of heater power until NO contacts reopen, or NC

contacts reclose (see figure 1.).

NOTE: Set switches S2, S3, and S4 as required, then initiate test with switch S1.

FIGURE 1. Timing circuit for normal operate time and saturate release time for NO and NC relays.

FIGURE 2. Instant release timing circuit (for NO relays only).