RELAY TERMINOLOGY
  • Image A black coil represents the energized state. For latching relays, schematic diagrams generally show the coil in its reset state. Therefore, the coil symbol is also shown for the reset coil in its reset state.
  • A single value (or narrow range) of source voltage intended by design to be applied to the coil or input. It is the voltage applied to the coil in order to make the relay work normally.
  • As the voltage on an un operated relay is increased, the value at or below which all contacts must function (transfer).
  • As the voltage on an operated relay is decreased, the value at or above which all contacts must revert to their un operated position.
  • It is refers to the maximum voltage which can be applied to the coil in the short time.
  • The value of current flow in the coil when nominal voltage is impressed on the coil.
  • The value of power used by the coil at nominal voltage. For DC coils expressed in watts; AC expressed as volt amperes.
    Nominal Power (W or VA) = Nominal Voltage x Nominal Current.
  • This is the DC resistance of the coil in DC type relays for the temperature conditions listed in the catalog. (Note that for certain types of relays, the DC resistance may be for temperatures other than the standard 20 °C 68°F.)
  • Denotes the contact mechanism and number of contacts in the contact circuit. Images Form A contacts are also called N.O. contacts or make contacts.
    Form B contacts are also called N.C. contacts or break contacts.
    Form C contacts are also called changeover contacts or transfer contacts.
  • Generally refers to the load which the contacts can switch reliably under the certain regulated conditions. Generally it is shown as the combination of the voltage and the current. The loads listed in the catalogue are resistive loads, unless otherwise stated.
  • The design value in watts (DC) or volt amperes (AC) which can safely be switched by the contacts. This value is the product of switching voltage x switching current, and will be lower than the maximum voltage and maximum current product.
  • The maximum open circuit voltage which can safely be switched by the contacts. AC and DC voltage maximums will differ in most cases.
  • The maximum current which can safely be switched by the contacts. AC and DC current maximums may differ.
  • The minimum value of voltage and current which can be reliably switched by the contacts. These numbers will vary from device type to device type. Factors affecting minimums include contact material, contact pressure, wipe, ambient conditions and type of relay enclosure (sealed vs. non-sealed), therefore the confirmation by actual load is suggested.
  • This is listed in the data column for each type of relay as the maximum value of the contact capacity and is an interrelationship of the maximum switching power, maximum switching voltage, and maximum switching current. The switching current and switching voltage can be obtained from this graph. For example, if the switching voltage is fixed in a certain application, the maximum switching current can be obtained from the intersection between the voltage on the axis and the maximum switching power.
  • The upper limit of power which can be switched by the contacts. Care should be taken not to exceed this value.
  • The resistance value between all mutually isolated conducting sections of the relay, i.e. between coil and contacts, across open contacts and between coil or contacts to any core or frame at ground potential. This value is usually expressed as "initial insulation resistance" and may decrease with time, due to material degradation and the accumulation of contaminants.
  • The maximum voltage which can be tolerated by the relay without damage for a specified period of time, usually measured at the same points as insulation resistance. Usually the stated value is in VAC (RMS) for one minute duration.
  • The elapsed time from the initial application of power to the coil, until the closure of the normally open contacts. (With multiple pole devices the time until the last contact closes.) This time does not include any bounce time.
  • The elapsed time from the initial removal of coil power until the reclosure of the normally closed contacts (last contact with multi-pole) this time does not include bounce.
  • Generally expressed in time (ms), this refers to the intermittent switching phenomenon of the contacts which occurs due to the collision between the movable metal parts or contacts, when the relay is operated or released.
  • The time period immediately following operate time during which the contacts are still dynamic, and ending once all bounce has ceased.
  • The time period immediately following release time during which the contacts are still dynamic, ending when all bounce has ceased.
  • The acceleration which can be withstood by the relay during shipping or installation without it suffering damage, and without causing a change in its operating characteristics. Usually expressed in "G"s.
  • The acceleration which can be tolerated by the relay during service without causing the closed contacts to open for more than the specified time. (usually 10 ms)
  • The vibration which can be withstood by the relay during shipping, installation or use without it suffering damage, and without causing a change in its operating characteristics. Expressed as an acceleration in G's or displacement, and frequency range.
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