2. Tutorial: Mechanic - electrician Topic: Basics of electrical engineering the 2nd. year Three-phase current Fuse Prepared by: Škarka Miloš Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

3. Fuse Is an electric device protecting an electro technical mechanism or circuit against damage by an excessive current and it is a component for protection by automatic disconnection from the source. Schematic symbol of the fuse Fuse insertion

4. How does it work? The principle of the securing means that fuse is the weakest link of the electric circuit. In case of warm up with higher than allowed current the conductor inside the fuse is blown and electric circuit is disconnected. Fuse (also fuse shell or fuse insertion) is disposable, has to be replaced after the disconnection, mustn't be repaired.

5. Division according to design Fuses for housing and similar installations In practice we use series marked DII (6 A, 10 A, 13 A, 16 A, 20 A, 25 A) and DIII (35 A, 50 A, 63 A). Ordinarily we can encounter fuses with thread E27 (Edison) up to 25 A and E33 (Goliáš) from 35 A. Normalized colors are: 2 A pink, 4 A brown, 6 A green, 10 A red, 13 A black, 16 A grey, 20 A blue, 25 A yellow, 35 A black, 50 A white, 60 a 63 A brown(copper), 80 A silver, 100 A red, 125 A yellow. Delimiting contact 10A Fuse head E27 Fuse - fuse shell 6A E27

6. Division according to design Cylindrical fuses Cylindrical ceramic element has pressed metal caps on edges as contacts. Both edges are the same. Current ranges are distinguishable only by printing, color or shape distinguishing aren‘t used. There are three dimensional series: 10×38 mm for currents 0,5–25 A, 14×51 mm for currents 2–50 A and 22×58 mm for currents 4–125 A. Fuses are set into fuse switches. Cylindrical fuse 100A Cylindrical fuse switches 10x38

7. Division according to design Nožové pojistky Power knife fuse For securing performance-higher circuits (for example with three-phase motors, whole houses) we use knife fuses. Knife fuses are most often marked PN... Or NH... They are manufactured in several dimensional series, which overlap with their current range. Standard sizes are marked PN000, PN00, PN1, PN2, PN3, PN4a. Fuse bottom parts Knife fuse 160A Knife fuse 35A

8. Other fuses Glass tube fuses are used for securing consumer electronics devices. Their values range from several tenths to several amperes. In cars and other vehicles there are usually plastic fuses with knife contacts. Tube fuse Vehicle knife fuses

9. Division according to disconnection characteristics Fuses are also divided into: fast - marked F Slow - marked T Knife and cylindrical fuses are manufactured for different operations L/gG secure in whole current range against overload and short-circuit. aM fuses secure against the short-circuit, not secure against overload. They are used for motor securing. gR for semiconductor securing and gTr for securing transformer are specialties rarely seen in common environment. gF1 for cable securing

10. Describe and explain: What is a fuse? How does the fuse work? What kinds of fuses according to design do you know? What is the fuse color marking?

11. Describe and explain: Pic no.2 Pic no.1 Pic no.4 Pic no.3 Pic no. 6Pic no.5

12. Literature http://http://www.oez.cz http://http://www.google.cz http://http://www.ghvtrading.cz http://http://www.elektro-paloucek.cz http://cs.wikipedia.org