Electrical Circuits and Electronics

Reading (Tu 8:00) – Doc. Ing. Jan Chyský, CSc

Lab. Exercises (Tu 16:00) – Ing. Josef Vlček, CSc

http://elektro.fsid.cvut.cz/en/

Literature:Chapman Stephen J.,  Electric Machinery Fundamentals, McGraw-Hill Publishing Company,  1985, ISBN 0-07-010662-2Crecraft D.I., Gorham D.A., Sparkes J.J., Electronics, Chapman&Hall 1993,ISBN 0-412-41320-5Rizzoni Giorgio, Principles and Applications of electrical Engineering, McGraw-Hill Publishing Company ISBN 0-256-26116-4Roadstrum William H., Wolaver Dan H., Electrical Engineering for All Engineers, John Wiley&Sons, Inc.,  ISBN 0-471-51043-2

First Part

Analysis of Electrical Circuits(Ohm’s law, Kirchhoff’s laws, loop and nodal analysis, principle of superposition. Thevenin’s and Norton theorems. Circuits supplied by DC and AC. Transient states in electrical circuits.

Second Part

Electronics(Semiconductors, diodes, transistors, thyristors, operating amplifiers.Basic analogue and digital circuits)

Electricity at work

National Grid

Serves for distribution of electrical energy from powerplants to consumers

Distribution Systém

AC and DC electricity

Voltage from batery is in one direction.Current flows from + lead to – lead

Voltage on coils terminal when the coil is turned in magnetic field.

Single and 3 Phase Generator

Delta connection

Star connection

One end of each phase coils is commonly linked to form a star or neutral point

Voltage between any phase line and neutral is 1/sqrt(3) times that between any two phases

phase/phase = 400 Vphase/line = 230 V

31

Distribution

Circuit protection

Means of isolating supply

Means of protection against axcess current

Means of protection against earth leakage

Circuit protection (2)

Fuses and beakers must be accomodated to load.For motors should be used other fuses than for bulbs

Personal protection

Preserve persons to injury by electric current.The injury causes current not voltage, but the voltage causes the current (Ohms law)

I = V/R

System earthing

Earth electrode Earthing

conductor Protective

conductor

System earthing (2)

System earthing (3)

TN-S systém

Uses separate protective

PE and neutral N

conductor

System earthing (4)

TN-C-S systém

Uses common

protective PE and

Neutral conductor

System earthing (5)

Earth leakage protection

Safety of work

Basic prescript - Law 50/1978 Sb

Divides persons according their qualification

§3 - Introduced workers

§4 – Instructed workers (students in universities labotarory)

Both paragraphs are valid for workers without electrotechnical educations

Safety of work (2)

TerminologyLiving parts (hot) serves for current

conducting, or aro under voltage or parts are conected vith voltage

Non-living are construction parts regulary without any voltage or current. Due to concern some voltage or current

may be there there

Safety of work (3)

Incidence of electric curent on body

Safety current

AC 15-100Hz

DC charge

1 mA 3 mA 0,5 C

parts which need NOT to be touch by personal during function

3,5 mA 10 mA 5O C

Magnitude of current, when it is not possible to release hand. Current causes paralysis, suffocation

>25 mA >100 mA ----

AC 15-100Hz DC Charge

Limited constant current parts which have to be touch by personal during function

1 mA 3 mA 0,5 mC

Parts which need NOT to be touch by personal during function

3,5 mA 10 mA 5O mC

Magnitude of current, when it is not possible to release hand. Current causes paralysis, suffocation

>25 mA >100 mA ----

Contact voltage Ud

Safety voltage

Area In contact ( during handling )

Safety voltage of living (hot) parts [ V ]

AC [V] DC [V]

Normal living 50 100

non living 50 120

Dangerous living 25 60

non living 50 120

Extra dangerous living 12 25

non living 25 60

Protection against dangerous voltage

1. Using isolation of living parts Basic isolation Suplementary isolation Double isolation

2. Using covering

3. Using barrier

4. Using position

Protection against dangerous voltage

5. Additional protection with current protector

6. Additional isolation (insulated pads, glove, etc.)

Protection using automatic disconnection in TN system

Uses fuse or circuit breaker for disconnecting power supply