Electricity And Electrical Safety

Transcription

1 Electricity And Electrical Safety Dr Shiv Kumar Singh Consultant Anaesthesia Royal Liverpool University Hospital

2 Knowledge is of two kinds: We know a subject ourselves, or we know where we can find information about it." Samuel Johnson

3 Today s Lec Basics of electricity Electrical and electronic components in anaesthesia equipments Electrical Safety: Principles and examples Electrical symbols: What do they mean and importance Diathermy: Principle and electrical safety issues

4 Basics of Electricity Conductors, insulators and semiconductors Current,Voltage & Resistance

5 Insulator Conductor ELECTRONIC CLASSIFICATION OF SOLIDS Semi-conductor

6 Conductors, Insulators and Semi-conductors Conduction band Conduction band Conduction band Forbidden band Forbidden band Valence band Valence band Valence band

7 Electric Field Direction Conduction Band Hole Forbidden Band Valence Band (Filled)

8 COUPLING HOLES ELECTRONS P TYPE SEMICONDUCTOR N TYPE SEMICONDUCTOR

9 Current flow

10 Electrons

11 Relation between current, voltage and resistance? Ohm s law

12 Potential difference T Resistance Flow I = V R

13 R = V --- I I V R I = V --- R V = I X R

14 The power supply

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16 Turbine Generator Steam Water Electricity Boiler Condenser

17 Magnet Induction Coils Live 1 Live 2 Live 3 Neutral Generator

18 Power POWER Station STATION Substation toaster Earth

19 Power POWER Station STATION Live Socket Fuse Substation Neutral Earth Plug Soil

20 R.M.S and Peak voltage U.K main Voltage: 230V [ 253 V (+10%) and 216 V (-6%)] R.M.S value of the voltage. The Peak Voltage: ( 2) x 240 V i.e 340 V

21 Square P o t e n t i a l Mean Square root Root mean square potential

22 Electricity Components & applications

23 Cell Capacitor Battery Resistor

24 Cell Battery Capacitor Resistor Transformer Inductor

25 Diode Transformer Amplifier Inductor

26 Capacitors

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28 V Insulator Capacitor plates Q α V Capacitance (C) = Q / V 1 F = 1 Coulomb / 1 Volt

29 Separation d Area A Capacitance α Area (A) Separation (d)

30 Charge Q Voltage V

31 Energy stored Q E = Q x V V Q α V C = Q/V or Q =C X V Area = Work done = ½ Q V But Q = CV Energy stored = ½ CV 2

32 Charge Q V Insulator E = ½ Q x V Voltage V Q α V C = Q/V or Q =C X V Area = Work done = ½ Q V But Q = CV Energy stored (E) = ½ CV 2

33 Capacitance and interference 50 Hz Capacitance link INSULATOR CONDUCTOR

34 Inductors

35 Inductors Magnetic field

36 Continuously varying magnetic field Alternating Current Inductor Switch

37 Inductance and interference Diathermy

38 Oscillator MAGNETIC FIELD CAPACITOR INDUCTOR

39 CAPACITOR INDUCTOR

40 Reactance and Frequency Capacitors And Inductors

41 Inductors Reactance Capacitor Frequency

42 Transformers Application of Inductance

43 PRIMARY COIL SECONDARY COIL V P V S N P N S V P / V S = N P /N S V S = V P x N S /N P

44 240 V 240 V 240 V 120 V STEP DOWN 240 V 480 V STEP UP

45 Diodes Semiconductors

46 Diodes

47 Bridge Rectifier Positive cycle Input Output Negative cycle

48 Defibrillators Circuit Waveforms

49 Charging Diode V Inductor

50 Diode V Inductor

51 Monophasic Current (Amps) Damped sine wave Time (msecs)

52 Biphasic Current (Amps) Biphasic Truncated Exponential - BTE (SMART, Philips) Time (msecs)

53 Biphasic Current (Amps) Rectilinear Biphasic waveform (Zoll) Time (msecs)

54 Biological signals Amplifiers & Filters

55 Amplifiers Device that responds to a small input signal (current, voltage, power) and delivers a larger output signal that contains the essential waveform features of the input signal. Amp

56 Single ended pre-amplifier Output Input Amp Ref earth

57 Single ended pre-amplifier Output Input Amp Ref earth

58 Differential / balanced pre-amplifier Input Inverting Non- Inverting Ref earth Amp Output

59 Differential / balanced pre-amplifier Inputs Amp Output Ref earth Noise

60 Input Output Inv Non Inv Amp Inv Non Inv Amp

61 Differential / balanced pre-amplifier Input Output RA I LA - Amp II III LL + + Ref earth

62 Interference Inv Non Inv - Amp + COMMON MODE REJECTION

63 Filters What are they? Why do we need them?

64 Filters Arrangement of electronic components that allow only those electric waves lying within a certain range, or band, of frequencies to pass and block others

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66

67 Output Frequency

68 Output Frequency

69 Output Frequency

70 High f Low f Amplifier

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72 Filters & amplifiers Channel? Filter Volume? Amplifier

73 Resistances Wheatstone Bridge

74 A R 1 R 3 C D R 2 R 4 B

75 A R 1 R 3 R 2 R 4 B R 1 R = 3 R 2 R 4

76 R 1 R v R 2 R 1 R 2 = R v R m R m = R 2 R 1 R v R m

77 R 1 R 2 R v R m

78 R 1 R 2 R v R m

79 R 1 R 2 R v R m

80 R 1 R v R 2 R m

81 12Kg 20 Kg?

82 R 1 R V Pressure R 2 R M Saline R 1 R 2 = R V R M R M = R V R1 R 2 Strain gauge Diaphragm

83 SIMPLE CIRCUIT BULB - + BATTERY SWITCH

84