CN101694934A

CN101694934A - Contactor with function of limiting short circuit current

Info

Publication number: CN101694934A
Application number: CN200910070852A
Authority: CN
Inventors: 姜和发
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-10-19
Filing date: 2009-10-19
Publication date: 2010-04-14

Abstract

The invention provides a contactor with a function of limiting short circuit current. The circuit structure of the contractor is realized in such a way that a contact K of the contactor is connected in series with a PTC element and a leak resistor R0 which are connected in parallel. The invention has the effects that the contractor with a function of limiting short circuit current is connected in a motor control loop to achieve evident circuit short circuit current limitation effect; 50KA current can be clamped below 3KA within 0.5ms; and a miniature circuit breaker (MCB) with less breaking capacity is used to protect the contactor within 10-20ms section by section, thereby not only protecting the contact of the contactor from fusion welding, but also reducing a half of investment by adopting a miniature circuit breaker (MCB) with 6KA breaking capacity.

Description

Contactor with function of limiting short circuit current

Technical field

The present invention relates to a kind of Low-voltage Electronic device, particularly a kind of contactor with function of limiting short circuit current.

Background technology

The control of motor and protection are low-voltage electrical apparatuses main an application of industrial control field, and it is made up of fuser motor A and contactor B two parts, and the former plays various protections and in failure condition incision deenergizing; The latter is started to control to make and is used.Its structure as shown in Figure 1.

A key technical problem of this combined electrical apparatus is the cooperation problem under short circuit current between contactor and motor circuit breaker.Promptly under the motor circuit short-circuit conditions, before the circuit breaker disjunction, probe of contactor should bear the ability of short circuit current.According to GB14048.4 and IEC60947-4 regulation, have two classes to cooperate and require: the 1st class cooperates requirement after short circuit, can continue behind the contactor renewal part to use, and does not cause people and equipment harm; The cooperation of the 2nd class requires the non-exchange part of contactor, people and equipment is not caused danger, can continue to use.

The 1st class compound mode, the circuit breaker of rated current and the combination of the contactor of rated current.During short circuit, the circuit breaker disjunction, protection people and equipment do not damage.But motor and contactor all might damage behind the short circuit, need to change, and not only investment, and influence production continuously, this is in steel-making, and industries such as chemical industry are unallowed.The combination of the 2nd class can be when short circuit, and contactor is had no progeny at the circuit breaker branch, remains intact, and can continue to use.But it is very difficult to satisfy the 2nd class cooperation, generally solves by the contactor of selecting big specification for use, and initial investment is big.

Summary of the invention

At structural deficiency in the prior art; the purpose of this invention is to provide a kind of contactor with function of limiting short circuit current; this contactor is connected in the motor control loop; when the motor fault that is short-circuited; under short circuit current 50KA current conditions; PTC in 0.5mS rapidly with the 50KA current clamp below 3KA; contactor can carry out the disjunction protection with the less miniature circuit breaker of breaking capacity (MCB) in 10-20mS; can protect not melting welding of probe of contactor; can adopt the miniature circuit breaker of breaking capacity 6KA to protect again, reduce investment.

For achieving the above object, the technical solution used in the present invention provides a kind of contactor with function of limiting short circuit current, and wherein: the circuit structure of this contactor includes contact K and the PTC element and the bleeder resistance R of described contactor ₀Back in parallel series connection.

Effect of the present invention is to adopt the contactor with function of limiting short circuit current; be connected in the motor control loop; the short circuit current limitation effect is obvious; can be wherein at 0.5m: in the time with the 50KA current clamp below 3KA; contactor can carry out the disjunction protection with the less miniature circuit breaker of breaking capacity (MCB) in 10-20ms; can protect not melting welding of probe of contactor, can adopt the miniature circuit breaker of breaking capacity 6KA to protect again, can reduce to invest half.

Description of drawings

Fig. 1 is the circuit breaker and the contactor combination schematic diagram of prior art;

Fig. 2 is PTC resistance one temperature characteristics of the present invention;

Fig. 3 is the contactor circuit schematic diagram with function of limiting short circuit current of the present invention.

Among the figure:

A, circuit breaker B, contactor

1, tentaculum contact K 2, PTC element 3, bleeder resistance R ₀

Embodiment

Reaching embodiment in conjunction with the accompanying drawings is illustrated the structure with contactor of function of limiting short circuit current of the present invention.

Shown in Fig. 2,3, the structure with contactor of function of limiting short circuit current of the present invention is: the circuit structure of this contactor includes contact K1 and the PTC element 2 and the bleeder resistance R of described contactor ₀3 back in parallel series connection.

The PTC element; be the resistance of semistor; the maximum characteristics of its temperature characterisitic are: when this material rises to the material Curie point in temperature; the starting point of positive temperature characterisitic is called Curie point; its resistance can suddenly increase with exponential form, thereby the electric current in the circuit is limited and protects.Its typical resistance one temperature characteristics as shown in Figure 2.

Organic macromolecule PTC thermistor then adopts the polymer resin (polymer) of processing and is distributed in conducting particles (carbon black) composition of the inside, have advantages such as matter is soft, resistivity at room temperature is low, now become the focus of the developing material development of PTC element, be called as " reusable fuse " (reset-able fuse).This series products is the desirable device that meets the solution overcurrent protection of IEEE-1394 standard.Organic macromolecule PTC thermistor is under normal condition, and polymer resin closely is strapped in conducting particles in the crystalloid structure, constitutes the chain conductive path, presents low resistive state.The heat energy that the PTC thermistor of flowing through on the circuit is produced is little, can not change its crystal structure.

When overload or short circuit took place circuit, the heat of the big electric current generation that semistor produced of flowing through made resin melt, and volume increases rapidly; conductive path is broken; form high-impedance state, loop current reduces rapidly, reaches short circuit or overload current protection purpose.Said process is reversible, thereby it is suitable as " reusable fuse " a kind of like this current-limiting apparatus.

The present invention organically makes up semistor with probe of contactor, make it have metering function, and the circuit breaker branch is had no progeny when reaching short circuit, and probe of contactor does not damage under first kind mated condition.

Contactor with function of limiting short circuit current of the present invention is achieved in that

Sequence number 1 is probe of contactor K as shown in Figure 3, and sequence number 2 is a semistor, and 3 is bleeder resistance R ₀With PTC and R ₀Connecting with probe of contactor in back in parallel.When being short-circuited, when having short circuit current to flow through probe of contactor K, same electric current also flows through semistor, the utmost point in the short time semistor temperature sharply rise.Because the PTC effect, the semistor limiting short-circuit current also consumes most of disjunction energy, cuts off circuit by circuit breaker at last, and meanwhile the semistor residual voltage passes through R ₀Release.When short circuit, not only protected probe of contactor like this, and reduced circuit breaker and cut off electric current, made circuit protection more safe and reliable owing to semistor has limited short circuit current.

Because PTC element current limiting capacity considers that probe of contactor and PTC element combine in the contactor arc-extinguish chamber, contactor is had bear the following function of electric current greatly of 50KA.

In the contactor arc-extinguish chamber PTC is connected with contactor fixed contact sheet, the contactor profile is constant.Because the PTC effect, the semistor limiting short-circuit current also consumes most of disjunction energy, cuts off circuit by circuit breaker at last, and meanwhile the semistor residual voltage passes through R ₀Release.When short circuit, not only protected probe of contactor like this, and reduced circuit breaker and cut off electric current, made circuit protection more safe and reliable owing to semistor has limited short circuit current.

Claims

1. contactor with function of limiting short circuit current is characterized in that: connect after the contact K (1) that the circuit structure of this contactor includes described contactor and PTC element (2) and additional resistance R0 (3) are in parallel.

2. the contactor with function of limiting short circuit current according to claim 1 is characterized in that: described PTC element (2) is a semistor.