Electrical Circuits and Electronics

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Electrical Circuits and Electronics

• Reading (Tu 800) Doc. Ing. Jan Chyský, CSc
• Lab. Exercises (Tu 1600) Ing. Josef Vlcek, CSc
• http//elektro.fsid.cvut.cz/en/

LiteratureChapman Stephen J.,  Electric
Machinery Fundamentals, McGraw-Hill Publishing
Company,  1985, ISBN 0-07-010662-2Crecraft D.I.,
Gorham D.A., Sparkes J.J., Electronics,
ChapmanHall 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 WileySons, Inc.,  ISBN
0-471-51043-2
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First Part

• Analysis of Electrical Circuits(Ohms law,
  Kirchhoffs laws, loop and nodal analysis,
  principle of superposition. Thevenins and Norton
  theorems. Circuits supplied by DC and AC.
  Transient states in electrical circuits.

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Second Part

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

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Electricity at work

• National Grid
• Serves for distribution of electrical energy from
  powerplants to consumers

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Distribution Systém
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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.

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Single and 3 Phase Generator
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Delta connection
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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
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Distribution
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Circuit protection
Means of isolating supply Means of protection
against axcess current Means of protection
against earth leakage
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Circuit protection (2)
Fuses and beakers must be accomodated to
load.For motors should be used other fuses than
for bulbs
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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

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System earthing

• Earth electrode
• Earthing conductor
• Protective conductor

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System earthing (2)
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System earthing (3)

• TN-S systém
• Uses separate protective
• PE and neutral N
• conductor

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System earthing (4)

• TN-C-S systém
• Uses common
• protective PE and
• Neutral conductor

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System earthing (5)

• Earth leakage protection

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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

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Safety of work (2)

• Terminology
• Living 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

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Safety of work (3)
Incidence of electric curent on body
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Safety current
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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 gt25 mA gt100 mA ----
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Contact voltage Ud
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Safety voltage
Area In contact ( during handling ) Safety voltage of living (hot) parts V 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
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Protection against dangerous voltage

• Using isolation of living parts
• Basic isolation
• Suplementary isolation
• Double isolation
• Using covering
• Using barrier
• Using position

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Protection against dangerous voltage

1. Additional protection with current protector
2. Additional isolation (insulated pads, glove, etc.)

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Protection using automatic disconnection in TN
system

• Uses fuse or circuit breaker for disconnecting
  power supply