MIL-PRF-28776 Relays, Hybrid, Established Reliability, General Specification ForThis specification establishes the general requirements for relays that use a combination of solid state circuit input elements functioning with an electro-mechanical relay that performs the switching functions associated with control system applications \(see 6.1\). These relays are designed to operate in low and medium power switching circuits with contact ratings up to 1 ampere alternating current \(ac\) or direct current \(dc\). The failure rate level is established at a confidence level of 90 percent for qualification and 60 percent for maintenance of qualification based on 100,000 cycles at +125┬░C under rated load conditions specified herein. Excludes time delay relays. CAUTION: The use of any coil voltage less than the rated coil voltage will compromise the operation of the relay. CAUTION: Pick-up, hold, and dropout voltages are for test purposes only and are not to be used as design criteria. For additional application and caution information, see 6.1.

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MIL-PRF-28776F

4.3.1 Power supply. Unless otherwise specified herein, the power supply shall have no more than 10 percent

regulation at 110 percent of the specified test load current. A dc power supply shall have no more than 5 percent

ripple voltage. An ac power supply shall be within 1 percent of the specified frequency and shall be sinusoidal with a

form factor between 0.95 and 1.25.

4.3.2 Grounding. Unless otherwise specified (see 3.1), the negative side of the dc power supply shall be

grounded. One side of single-phase ac power supply shall be grounded.

4.3.3 Load conditions during tests. The coil of the relay being tested shall be connected to a power supply

separate from the load power supply. The loads of the relay being tested shall be connected individually to each

stationary contact. The polarity of the load power supply is optional. The movable contacts of the relay being tested

may be connected to either the high or low side of the load power supply. All tests during which the contacts are

loaded and being cycled, except dielectric withstanding voltage, shall be conducted with the case of the relay

connected to the power supply ground or neutral through a normal blow fuse rated at 5 percent of the contact load

maximum, but not less than 0.100 ampere. For relays with nongrounded case ratings, tests for isolated-case ratings

may be made with the case electrically isolated from the power supply ground.

4.3.4 Input conditions during test. Unless otherwise specified, the relay is turned on when rated coil supply voltage

and control signal voltage is applied. The relay is turned off when rated coil supply voltage is applied but the control

signal voltage is turned off.

4.3.5 Testing devices. Unless otherwise specified herein, devices used in the testing of relays shall not load the

contacts above 10 mA resistive at 6 V dc or peak ac maximum open circuit.

4.3.6 Mounting relays for ambient temperature tests. When the relays are subjected to the tests specified in

4.8.19 and 4.8.14 (intermediate current and coil life, respectively), they may be mounted on a heat sink in accordance

with the following:

Each relay may be attached by its normal mounting means to a .062 inch (1.57 mm) thick minimum, flat

aluminum plate heat sink. The heat sink shall be designed to place every relay in the center of its own

square space whose total surface area (both sides) is eight times the outside surface area of the relay,

excluding mounting. Relays without mounts shall be held to the heat sink with a metal strap .25 inch (6.35

mm) wide by .015 inch (0.38 mm) maximum thickness. The heat sink assembly shall be suspended by twine

or other nonheat conducting material. The leads shall not constitute a heat sink.

Chamber temperature shall be controlled to maintain the temperature at the specified ambient extremes

(see 3.1).

4.3.7 Methods of examination and test. Application of coil power to relays under test shall be such that plus

polarity is applied to the color coded terminal when applicable; or to the lower numbered terminal when color coding

is not used.

4.3.8 Reliability requirements. The reliability requirements specified herein are in accordance with MIL-STD-690.

The confidence level for qualification is 90 percent and the confidence level for maintenance of qualification is 60

percent.

4.3.9 Tolerances. Unless otherwise specified (see 3.1), all electrical, environmental, and mechanical parameters

shall have a tolerance of �10 percent.

4.3.10 Alternate test equipment. Test circuits and test equipment herein are intended to provide guidance to the

relay manufacturer. Use of any alternate test circuits or test equipment shall be approved by the qualifying activity

prior to use.

4.4 Qualification inspection. Qualification inspection shall be performed at a laboratory acceptable to the

Government (see 6.3) on sample units produced with equipment and procedures normally used in production.