Delixi Relays can be divided into single side steady state type, single coil self holding type and double coil self holding type.
Unilateral steady state relay (common relay): when the coil of unilateral steady state relay is powered on, the relay will be set, and when the coil is powered off, it will be reset;
Single coil self holding type: the single coil self holding type relay has a self holding structure. After a positive pulse is input on the coil, the relay will remain in the set state, and when a negative pulse is input, the relay will reset;
Double coil self holding type: The self holding structure of double coil self holding type relay is composed of two coils, the setting coil and the reset coil. If pulse is added to the setting coil, the relay will be set, and if pulse is added to the reset coil, the relay will be reset.
Self holding relay has a good power saving function compared with ordinary relay, so more and more common relays are accepted by users.
Circuit breaker It refers to the equipment that cuts off the current, which is equivalent to a tap. It controls the water flow, while the circuit breaker controls the current.
The circuit breaker is mainly used to protect the circuit from short circuit current. When a short circuit occurs in the circuit, it will immediately disconnect the circuit to protect the safety of the load. The rated breaking capacity of circuit breaker is divided into rated limit short-circuit breaking capacity and rated operating short-circuit breaking capacity.
The national standard Low Voltage Switchgear and Control Equipment Low Voltage Circuit Breakers (GB14048.2) explains the rated ultimate short-circuit breaking capacity and rated operating short-circuit breaking capacity of circuit breakers as follows:
(1) Rated ultimate short-circuit breaking capacity (Icn) of the circuit breaker: according to the conditions specified in the specified test procedure, excluding the breaking capacity of the circuit breaker to continue to carry its rated current capacity;
(2) Rated operating short-circuit breaking capacity (Icn) of the circuit breaker: according to the conditions specified in the specified test procedure, including the breaking capacity of the circuit breaker to continue to carry its rated current capacity;
(3) The test procedure of rated ultimate short-circuit breaking capacity (Icn) is O-t-CO. The specific test is to adjust the current of the line to the expected short-circuit current value (such as 380V, 50kA), and the test Button If it is not closed, the tested circuit breaker is in the closing position. Press the test button, the circuit breaker will pass the 50kA short circuit current, and the circuit breaker will immediately open (O for short). The circuit breaker should be intact and can be re closed. T is the intermittent time, generally 3min. At this time, the line is still in the hot standby state, and the circuit breaker is closed again (referred to as C for short) and then opened (O for short) (the closing test is to assess the electrical and thermal stability of the circuit breaker under peak current). This procedure is called CO. If the circuit breaker can completely break, its limit short-circuit breaking capacity is qualified.
(4) The test procedure for rated operating short-circuit breaking capacity (Icn) of circuit breaker is O-t-CO-t-CO. It has one more CO than Icn's test procedure. After the test, the circuit breaker can completely break and extinguish the arc, so its rated operating short-circuit breaking capacity is qualified. Therefore, it can be seen that the rated limit short-circuit breaking capacity Icn refers to that the low-voltage circuit breaker can operate normally and break the short-circuit current again after breaking the maximum three-phase short-circuit current at the outlet of the circuit breaker. As for whether it can be normally connected and disconnected in the future, the circuit breaker will not guarantee; The rated operating short circuit breaking capacity Ics refers to that the circuit breaker can break normally for many times when the maximum three-phase short circuit current at its outlet occurs.
IEC947-2 Low voltage Switchgear and Control Equipment Low voltage Circuit Breakers stipulates that Ics of Class A circuit breakers (referring to circuit breakers with only overload long delay and short circuit transient) can be 25%, 50%, 75% and 100% of Ics. Ics of Class B circuit breaker (circuit breaker with overload long time delay, short circuit short time delay and short circuit instantaneous protection) can be 50%, 75% and 100% of Ics. Therefore, it can be seen that the rated operating short-circuit breaking capacity is a breaking current value smaller than the rated limit short-circuit breaking current, and Ics is a percentage of Icu. Generally speaking, circuit breakers with overload long time delay, short circuit short time delay and short circuit instantaneous action three section protection functions can achieve selective protection, and most trunk lines (including the outgoing line end of the transformer) use it as the main protection switch. Circuit breakers without short circuit short delay function (only overload long delay and short circuit instantaneous two section protection) cannot be used for selective protection, and they can only be used for branch circuits.
IEC92 Marine Electrical pointed out that the circuit breaker with three section protection focuses on its operating short-circuit breaking capacity, while the circuit breaker used for branch lines should ensure that it has sufficient limit short-circuit breaking capacity. No matter what kind of circuit breaker is, it has two important technical indicators, Icu and Ics. However, as the circuit breaker used on the branch line, it can only meet the rated limit short-circuit breaking capacity. Now there is a common bias that it is better to take the big than the right one, and that it is better to take the big insurance. However, excessive gains will result in unnecessary waste (for the same type of circuit breaker, the price of H-type high breaking type is higher than that of S-type ordinary type.
