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Selecting the correct rating |
Determine amperes load of your equipment when operating under normal voltage and full load running conditions. Select circuit breaker with next higher amps rating (standard current rating). In case of high ambient conditions, or D.C. loads (rectified Half wave or full wave) consult us for correct rating.
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| Why use Circuit Breakers |
When electrical equipment is drawing excess load, the use of a precision circuitbreaker is the only way of protecting it against damage. A fuse provides very little protection because it will not operate unless there is very heavy overload or short circuit. A fuse cannot be set for a slight overload because then it will blow as a result of starting current or any short duration surge or line current variations, which are quite common, but which do not damage equipment. For example a 1/2 HP single phase AC motor drawing 4 amps full load current cannot be protected with a 6 amp. fuse, because the fuse is liable to blow even during start up. Further, during continuous sustained overloads of say 5 amps., the fuse offers no protection, though the motor is sure to burnout. But a 4 amp. circuitbreaker will provide full protection whether the load is 5 amps. or much more.
A fuse needs replacement once it has operated. A curcuitbreaker, when tripped, is again ready for use by pushing the reset button. It does not need replacement. Furthermore, often an exact replacement fuse is not available, consequently a wrong rating fuse is put, resulting in subsequent problems. Generally an overrated fuse is put, resulting in damage. Further, there is no visual indication of a blown fuse, But a circuitbreaker has visual indication when it has tripped.
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| Effect of Ambient Temperature |
Since, these devices are thermally operated, they are sensitive to ambient temperature and the tripping time will reduce as the ambient temperature rises. This characteristic provides accurate protection to equipment when operating in high ambients and likely to suffer overheat damage, because the circuitbreaker will trip earlier. Conversely in low ambients the equipment will take longer to heat up, and the circuitbreaker trip time also is extended, thereby permitting maximum utilization of the overload capability of equipment and avoiding nuisance tripping.
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| Overload Switching Capacity and Back-up Fuses |
| Up to 600% of rated current of the circuitbreakers (maximum 60 amps) can be interrupted. Since these devices have an inherent time delay before switching off, there is a possibility that in some applications where there may be overload or short-circuit far in excess of the overload switching capacity the circuit breaker may get damaged. In such cases a back-up fuse may be connected in series. The fuse rating can be up to 4 to 6 times the rating of the circuitbreaker. |
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