Short Circuit Isolator:CFT-957

Short Circuit Isolator:CFT-957

I. Overview

  CFT-957short circuit isolators are used for the short circuit fault protection ofbuses. When a bus circuit is operating normally, the GL-957 short circuitisolator will not operate; when a short circuit fault occurs at a place at theoutput end of the short circuit isolator in the bus circuit (short-circuitcurrent 200mA), the section suffering the shortcircuit fault will be cut off from the bus, thus ensuring the normal communication of the other sections of the bus. Upon elimination of the shortcircuit fault, the short circuit isolator can automatically bring the isolatedsection into the system again. A short circuit isolator will make it convenientto confirm the location suffering a short circuit fault. The short circuitisolator does not needcoding nor occupies the address in the bus circuit.

II. Main technical parameters

1.     Modeof operation: Nonpolar two-wire system

2.     Quiescentcurrent: 5.0mA

3.     Operative current: 200mA

4.     Operationindicator: Red (It is out in the normal monitoring status or remains lit in theoperation status)

5.     Operating environment: Temperature: 1050; relative humidity: 95% (40±2, withoutcondensation)

6.     Externaldimensions: 86×86×40mm (with the base)

7.     Weight:about 125g (withthe base)

III. Instructions for use

1.      Outside drawing (Fig.1)

Short Circuit Isolator:CFT-957

Fig.1Main Body of a CFT-957Short Circuit Isolator

2.      Schematic diagram of theterminals on the base of a short circuit isolator

Short Circuit Isolator:CFT-957

Fig.2 Base of a CFT-957 Short Circuit Isolator

Terminal description:

Terminal No.


Terminal No.



Bus input


Bus output


Bus input


Bus output

3.      Wiring method

 Short Circuit Isolator:CFT-957                       


4.      It is recommended to arrange32 or less intelligent detectors (or intelligent modules) at the output end ofa short circuit isolator.

IV. Installation anddebugging

1、 Make sure the type of the module matches thetype given on the construction drawings.

2、 Conduct correct wiring as instructed in Fig.2or Fig.3.

3、 Use two M4 screws to fix the module base viathe two elliptic screw holes shown in Fig.2, and then insert the main body ofthe module into the module base and make sure they contact properly.

4、 After the short circuit isolator is installedand checked, connect the power supply of the controller. Conduct automaticlogin to the intelligent terminal connected to the output end of the shortcircuit isolator. Upon successful login, the intelligent terminal’s inspectionindicator will blink once about every 12 seconds, which suggests that the shortcircuit isolator has begun to operate.

5、 Conduct debugging after the installation iscompleted. Make the output end of the short circuit isolator short. After that,the short circuit isolator will start to operate immediately, the red indicatorwill be lit, the intelligent terminal at the output end of the short circuitisolator will continually report loss and the circuit board will not report ashort circuit fault. About 10 seconds after the elimination of the shortcircuit fault, the short circuit isolator should be able to restore its normaloperation and the intelligent terminal at its output terminal should be able torestore its normal operation, too.

V. Precautions

1、 The concatenation application of multipleshort circuit isolators is not supported. If such concatenation is done, theshorting of the end of the post stage short circuit isolator will make theshort circuit isolators keep operating and restoring and the bus operatingabnormally.

2、 If the controller is reset after a shortcircuit occurs within 10 seconds or the output end of the short circuitisolator is shorted, the short circuit isolator may first restore for about onesecond after it starts to operate and then maintain the operation status.

3、 In case of a slight short circuit fault inthe bus circuit, the short circuit isolator will not always start to operate asit will start to operate when the short-circuit current of the load is largerthan the design value. So, if the short circuit isolator is not operating, itcannot be evidence that there is no slight short circuit fault in the buscircuit.