Main technical parameters of fuse
Feb 10, 2022
1. Protection characteristic curve (ampere second characteristic curve)
Characterizes the relationship between the current flowing through the melt and the melt break time. It's an inverse time curve.
Minimum melting current Ir-the current at the dividing line between the fusing current and the non-fusing current, i.e. the minimum current that can cause the melt to fuse within 1-2h according to the requirements of fuses, the melt should never fuse at rated current. Rated current.
Minimum melting coefficient - the ratio of the minimum melting current to the rated current of the melt. It is an indicator of the sensitivity of a fuse to protect against small multiple overloads.
(When the current through the melt is 1.3 times the rated current. The melting time of the melt is more than 1 hour, and it should be fused within 1 hour when passing 1.6 times of the current; the melting is almost instantaneous when passing 2 times of the rated current. The relationship between the current passing through the melt and the fusing time has an inverse time characteristic.
From the point of view of overload protection, small P is beneficial to small multiple overload protection. For motor overload protection, the best P value is between 1.2 and 1.4.
2. Breaking ability
Usually refers to it in the rated voltage and a certain power factor (or time constant) under the cut-off short-circuit current limit ability.
: is often expressed by the limit break current value (the effective value of the periodic component).
The ampere-second characteristic curve mainly serves for overload protection, while the breaking capacity mainly serves for short-circuit protection, and the former needs reverse time. The latter requires transient current limiting characteristics.
3, pay attention to
It is ideal for short circuit protection, but not for overload protection of motor.
· 19-(4-7)I for AC asynchronous motors
In order for the melt not to fuse when the motor starts, the rated current of the melt must be much higher than the rated current, so that the fuse cannot play the role of overload protection when the motor is overloaded in operation.
