Should I choose a slow-blow or fast-blow fuse for the power module?[Copy link]
Fuses can be divided into many types. The following mainly discusses the issues of slow-blow and fast-blow. Fast-blow fuses will melt instantly as long as the current exceeds its rated value, and can only provide short-circuit protection. Slow-blow fuses will remain intact when non-fault pulse currents appear in the circuit, and protect against long-term current overloads. They also have short-circuit and overload protection functions. The main difference between fast-blow fuses and slow-blow fuses is their ability to withstand instantaneous pulse currents. Technically speaking, slow-blow fuses have a larger melting heat energy value, and the energy required to blow the fuse is larger. For fuses with the same rated current, slow-blow fuses are much more pulse-resistant than fast-blow fuses. Because slow-blow fuses are larger than fast-blow fuses of the same specification, when overcurrent occurs in the circuit, the melting time will be slower than that of fast-blow fuses. Fast-blow and slow-blow fuses are often used in different circuits because of their differences. For example, fast-blow fuses must be used in pure resistive circuits (no or little surge) or circuits that need to protect sensitive devices such as ICs, while slow-blow fuses are best used in capacitive or inductive circuits (surges when switching on and off) and power input and output parts. In addition to protecting IC circuits, most occasions where fast-blow fuses are used can be replaced with slow-blow fuses to improve their anti-interference capabilities. However, if fast-blow fuses are used in places where slow-blow fuses are used, the fuse will break when the machine is turned on. In actual applications, power modules often have surge currents or impact currents, that is, the current of some circuits at the moment of switching will be several times higher than usual, and the current peak is generally very high and appears for a short time. Normal ordinary fuses cannot withstand this current. If used, the circuit will not start normally. Replacing with a large-size current fuse will cause the circuit to be unable to protect when overload current occurs. Therefore, choosing a slow-blow fuse can solve this problem, avoiding the module from blowing when the instantaneous current generated at the moment of startup exceeds its limit value, instead of blowing at the moment of startup, but only when it exceeds the limit value continuously. It should be noted that if the fuse is too small, it is easy to cause false melting, and if it is too large, it cannot provide protection, which may cause a circuit input short circuit and cause power supply interruption.
TT is used to represent the extra slow fuse, T is used to represent the slow fuse, M is used to represent the medium-speed fuse, F is used to represent the fast fuse, and FF is used to represent the extra fast fuse.
qwqwqw2088 posted on 2019-3-18 14:23 Extra slow fuses are represented by TT, slow fuses are represented by T, medium fuses are represented by M, fast fuses are represented by F, and extra fast fuses are represented by FF
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