Relays conforming to this specification are intended for use in direct or alternating current (single or multiphase) electrical systems as a means of controlling the making and breaking of circuits for electrically operated equipment and devices. Their principal areas of application are aircraft, missiles, spacecraft, and ground support equipment. This does not preclude the use of these relays in other military applications.

CAUTION: The use of any coil voltage less than the rated coil voltage will compromise the operation of the relay.

CAUTION: Transfer relay contacts should not be used to ground the load in one position and to the 115 volt terminal in the other position. Transfer relay contacts should not be used to transfer loads between phases or between unsynchronized ac sources.

CAUTION: When latching relays are installed in equipment, the latch and reset coils should not be pulsed simultaneously. Coils should not be pulsed with less than the rated coil voltage, and the pulse width should be a minimum of three times the specified operate time of the relay. If these conditions are not followed, it is possible for the relay to be in the magnetically neutral position.

Contact rating.

The contact ratings of relays covered by this specification are based on load life tests which establish the relay capability to switch rated loads. For the purposes of this specification, contact load ratings are defined as follows:

a. Low level: 10 μA to 50 μA at 10 mV to 50 mV.

b. Intermediate: 10 mA at 6 V to 100 mA at 28 V.

c. High level: Above 100 mA at 28 V.

Contact voltage rating.

Users of relays are cautioned that a 115/200 volt rating indicates that the relay is designed for use in a three-phase system. The relay may not be capable of having 200 volts applied per pole across the one set of contacts. Prior to using relay with such a rating in a circuit where it is required to interrupt 200 volts across an individual set of contacts, the manufacturers of the relay should be consulted.

Load transfer rating, three-phase ac.

Unless a load transfer three-phase ac rating specifying both current and system voltage is on the specification sheet, relays are not to be used in three-phase load transfer applications.

Capacitive loads.

A capacitor load or any load having a capacitor in parallel, can theoretically sustain an infinite current during switching transients. Therefore, the total circuit must be analyzed to determine the circuit impedance including wire resistance and power supply impedance in series with the capacitor, and the peak supply voltage (ac or dc). In order to ensure that this current will not weld the contacts, a relay should be specified which has a motor load rating that is greater than 18 percent of the peak switching current. A second detrimental phenomena associated with the capacitive loads and dc power supplies affects the number of life cycles. The arc generated during contact bounce when closing contacts will transfer material from one contact to the other. Since the break current is very low, the material transferred tends to build up like a stalactite leaving a corresponding cavity on the mating contact. (With loads having break currents, the materials tend to disperse (smooth out) during contact break.) After a number of cycles, the stalactite will catch in the cavity and the contacts will not open. Thus, the number of life cycles may be reduced. Since it is difficult to predict the total life cycles for a relay used under these conditions, it is recommended that the applications engineer contact the manufacturer and discuss any applications where the inrush current is greater than the motor load divided by 18 percent.