Relay Term Popularization

Relay Term Popularization

1. Contact Parameters

1.1 Contact form: it is a description of relay contact state and pole numbers, among which there are generally three forms of contact state, namely normally open type, normally closed type and transition type, and group number is generally 1 pole, 2 poles, and 3 poles.

1.2 Contact resistance: It refers to the total resistance between contact points, the sum of the reed connected to contact and the conductor resistance at the leading end, which is generally expressed as mΩ.

1.3 Contact drop: Generally refers to the total voltage drop between contact points and the reeds connected to contact points and on the leading end of a load circuit.

1.4 Contact material: The material used for a contact, usually expressed in a chemical formula, such as AgNi for a silver-nickel alloy contact.

1.5 Contact rated load: Generally refers to the load under certain specified conditions that the contact can switch reliably. It is generally expressed as a combination of voltage and current. Unless otherwise specified, the load listed in the specification is generally a resistive load.

1.6 Surge current: Generally the maximum instantaneous current at which a relay contact can withstand a particular type of load. 

2. Performance parameters

2.1 Insulation resistance: The impedance at which a specified voltage is applied between the disconnected conducting parts, generally expressed in terms of MΩ. The specified voltage above is generally 500Vd.c.(or 250 VDC)

2.2 Dielectric withstand voltage: the voltage at which the leakage current is less than the specified value when the voltage is applied between the disconnected conducting parts for a specified period of time. The specified voltage is generally the valid value of the ac voltage. Unless otherwise specified, the leakage current is generally defined as less than 1mA.

2.3 Pick-up time: refers to the time of the relay in the release state from the moment when the rated voltage is applied to the coil to the moment when the normally open contact of the relay closes (excluding the time of pick up and return jump), generally expressed as "ms".

2.4 Release time: refers to the time of the relay in operation from the moment when the rated voltage applied on the coil is disconnected to the moment when the normally closed contact of the relay is opened (excluding Release bounce time), generally expressed as "ms".

3. Coil parameters

3.1  Rated coil power: Refers to the power consumed by the coil when the rated voltage is applied to the coil. Generally, dc relays are denoted by W and AC relays by VA.

3.2 Rated voltage: refers to the voltage applied on the coil in order to make the relay work normally, generally expressed as V for the polarized relay, attention should be paid to the direction of the applied voltage.

3.3 Operating voltage: refers to the relay in the release state (the reversion state for the magnetic latching relay), which gradually increases the voltage on the coil. When the normally open contact is closed, the voltage is generally expressed as V, and the maximum value is given in the general instruction, which is about 80% of the rated voltage.

3.4 Release voltage: refers to the relay in the operating state, the voltage on the coil is gradually reduced from the rated voltage, when the normally closed contact is opened, the voltage is generally expressed in V, the general instruction gives the minimum value, about 10% of the rated voltage.