How many ohms should a fuse have?
If the reading is between 0 and 5 Ω (Ohms), the fuse is good. A higher reading indicates a bad or degraded fuse. A reading of OL (Over Limit) definitely means a blown fuse. If the fuse is blown, replace the fuse with one that is exactly the same (see panel).
How many ohms should a 20 amp fuse have?
You are checking to see if there is continuity through the fuse element. A reading of approximately 0.5 on a digital meter’s LCD indicates a good fuse. Most digital meters read their own internal fuses resistance, hence 0.5 Ohms and not 0.00 Ohms.
What is the resistance of a fuse?
For a fuse wire which is about 5 cm long and has about 1 mm^2 surface area its resistance is between 0.00075 ohm and 0.005 ohm ( , where R is resistance, is resistivity, l is wire length and S is surface area). In a physical way of speaking it means all fuse wires have about the same resistance.
Should a fuse have resistance?
A fuse wire should have a high resistance so that according to (1), a lot of heat is generated and it is easier for the fuse wire to reach its melting point. Also, a high resistance decreases the current flowing in the circuit than what would have been in the absence of it.
Does a fuse increase resistance?
A traditional wire fuse works using dissipated power P = I²R. When the current reaches the prescribed level then the power dissipation is enough to heat the fuse wire, increasing the resistance of the wire with temperature (all metals get higher resistance with temperature), which in turn dissipates more power.
Should a fuse show resistance?
A good fuse will generate the same reading. When the tips are seperated, the needle will show 100% resistance state. A blown fuse will generate the same reading. Make sure that the testing lead tips make a good connection to the metal end caps or blades of the fuse and the fuse is tested on a non-conducting surface.
How is the resistance of a Fuse considered?
Refer to the section on PULSES in the FUSE SELECTION GUIDE. RESISTANCE:The resistance of a fuse is usually an insignificant part of the total circuit resistance. Since the resistance of fractional amperage fuses can be several ohms, this fact should be considered when using them in low-voltage circuits.
What should be considered when selecting a fuse?
Refer to the section on PULSES in the FUSE SELECTION CHECKLIST. RESISTANCE: The resistance of a fuse is usually an insignificant part of the total circuit resistance. Since the resistance of fractional amperage fuses can be several ohms, this fact should be considered when using them in low-voltage circuits.
How many amperes does a fuse need to have?
Fuses listed in accordance with UL/CSA/ANCE 248 are required to have an interrupting rating of 10,000 amperes at 125V, with some exceptions (See STANDARDS section) which, in many applications, provides a safety factor far in excess of the short circuit currents available.
How long does it take for a fuse to open?
The fuse must carry 100% of its ampere rating and must stabilize at a temperature that does not exceed a 75ºC rise. The fuse must open at 135% of rated current within one hour. It also must open at 200% of rated current within 2 minutes for 0-30 ampere ratings and 4 minutes for 35-60 ampere ratings.