1.6 Relay Coil and Contact Symbols

Commonly used symbols for relays of various kinds and applications are illustrated in Figure 1.6 and 1.8 through 1.12. (ANSI Y32.2)

Fig. 1.6 Symbols for Relay Contact Combinations established by the American National Standards Institute (ANSI).


The heavy arrow indicates the direction of operation. Contact chatter may cause some electrical discontinuity in forms D and E. Symbols taken from ANSI C83.16-1971 and Y32.2-1975.
The proper polarization for a polarized relay is shown by the use of plus (+) and (-) designations applied to the winding leads. The current in the direction indicated is to be interpreted to move, or tend to move, the armature toward the contact shown nearest the coil on the diagram. If the relay is equipped with numbered terminals proper numbers should be shown.
The following relay abbreviations are to be used on elementary wiring diagrams drawn according to the Joint Industry Conference Standard for Industrial Equipment (JIC):

TYPE OF RELAY DESIGNATION
General use CR (1CR, 2CR, etc.)
Master CRM
Automatic CRA
Electronically Energized CRE(1CRE, 2CRE)
Manual (pushbutton) CRH
Latch CRL (1CRL, 2CRL)
Unlatch CRU (1CRU, 2CRU)
Time delay TR (1TR, 2TR)
Overload relay OL (1OL, 2OL)
Motor starter M (1M, 2M)

Fig. 1.7 Preferred contact arrangement in a relay pileup.

Fig. 1.8 Symbol used in motor control relay circuits (JIC-NMTBA).



(a) Two wire control is generally thought of in relation to a pilot device such as a thermostat, pressure switch, etc., or to a simple maintained SPDT toggle or push-button switch. As the term implies, these devices require the use of only two wires between the control unit and the starter. The device is connected in series with the main contactor coil of the starter and the opening or closing of the pilot device directly controls the de-energizing or energizing of the starter. The major feature of a two wire control system is low voltage release. The starter drops out in the event of a power failure but picks up or recloses automatically when the power is restored, (b) In three wire control the main contactor coil of the starter is wired in series with its own NO auxiliary contacts. The "Start-Stop" push-button station, which requires the use of three wires between the control and the starter, is connected in parallel with the coil. In the event of a power failure, the starter will drop out and remain de-energized until the "Start" button is depressed. Since the starter drops out when there is a power failure and will not pick up or reclose again until the start button is depressed, this Control system provides low voltage protection.
Graphic Symbols is DoD mandatory. Section 22 covers letter designations for components and "K" is the letter for relay-e.g., K1,K2,etc. See Footnote to paragraph 1.1.

Fig. 1.9 Alternative symbols for relay contact combinations.

Sources of symbols: IEC-International Electrotechnical Commission; JIC-Joint Industry Conference, Electrical Standards for Industrial Equipment; NMTBA - National Machine Tool Builders Association/Electrical Standards. Mod. Tel-Modern telephone practice. Note: CT indicates continuity transfer, one asterisk denote Make-Before-Break, and two asterisks denote Break-Make-Before-Break.

Fig. 1.10 Combined symbol of relay coil and its contacts.

APPLICATION: RELAY WITH TRANSFER CONTACTS

Fig. 1.11 Comparison Relay, Electronic and Logic symbols.


Fig. 1.12 Symbols used in cam-operated timer control.