13 – CONTROL CIRCUIT COMPONENTS

13 – CONTROL CIRCUIT COMPONENTS

13 – CONTROL CIRCUIT COMPONENTS

13 – control circuit components

13 – control circuit components

13 – CONTROL CIRCUIT COMPONENTS of large overloads and short circuits the small cross-section of the fuse element melts quickly and opens the circuit. Fig. 2 . 3 shows the typical time characteristic of a HRC fuse . Fuses are provided into the circuit through fuse base and fuse carriers generally made of bakelite material . Fuse is inserted in the fuse carrier which is then fixed into the fuse base . Figure 2 . 4 ( a ) shows the power circuit for a motor . It includes four necessary elements for the control and protection of motor. None of the items used can be eliminated as they incorporate four basic functions very different in nature . Switch : To isolate the circuit for repairs and maintenance , Fuse/Fuse base: To provide short circuit protection, Contactor : To achieve automatic on-off of motor, Overload relay : To protect the motor against overloading. Development of a new type of switch gear, called fuse switch unit, has led to the use of a modified power circuit as shown in Fig . 2 . 4 ( b ) . This fuse switch unit came into existence when the fuse base was integrated with switch . The advantages of using fuse switch unit are that the number of electrical joints becomes less due to the elimination of one element from the circuit and hence requires less maintenance , and the space occupied is less as the combination fuse switch occupies less space than fuse / fuse base and switch when used separately.

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