A Short Circuit Protection Method Using Ordinary Luminous Body Instead of Relay

Abstract

The invention provides a short circuit protection method using a common luminous body for replacing a relay. Specifically, a luminous component is used for replacing the relay and is in series connection with a PLC output circuit. The current capacity of the luminous component is lower than the rated capacity of the current of a PLC. When a controlled operation station works normally, the luminous component is not lightened; when the controlled operation station has a short circuit, namely a load current is overloaded, and the overcurrent is lower than the rated capacity of the PLC, the luminous component is lightened slightly. When the overcurrent is higher than the rated current of the PLC for a certain reason, the luminous component is broken by burning or fusing, namely the current in a circuit is restricted at the rated current of a bulb, therefore, the relay does not need to be used, the PLC is used directly for driving a load, and the PLC cannot be burnt out even if the load has a short circuit. Meanwhile, the luminous component which is used has the advantages of reducing cost, adding the alarm display function and being convenient to replace.

Description

technical field [0001] The invention relates to a method for replacing a relay with a common luminescent component, which is used in an external circuit of a PLC to serve as a short-circuit warning and protection function when the load short-circuit current is less than the PLC rated current, and when the load short-circuit current is greater than the PLC rated current Directly fusing or burning the light-emitting components, which is used to protect the entire control circuit and protect the PLC from being burned out. Background technique [0002] At present, in some high-current and high-voltage control circuits, PLC programmable controllers can control the operation of various equipment through programming, so they have been widely used. However, since the output contacts are integrated inside, once the control object is short-circuited, the internal contacts will be burned out by a large current, and in severe cases, the copper strips of the printed circuit will be burnt...

AI Technical Summary

Problems solved by technology

Its disadvantages are: the cost of the external relay is increased, and because the external relay has a certain failure rate, it does not reflect the advantages of reliable equipment and reduced failure rate after the PLC is installed.

[0004] However, the current relays also have some shortcomings in the process of use. For example, when the current and voltage value of the driving load is small, the relay does not need to output a large current for expansion. The price is relatively high, which will increase the cost in the production and application process of the enterprise. The relay has no alarm function when the load is short-circuited, and the operator cannot find the overload phenomenon and the overloaded part or line in time. After the PLC is connected to the external relay, the control panel is not clean. , it is not convenient to replace the relay

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