Download AVOP-ELEKTRO-SMI-004

Tutorial :Mechanic - electrician
Topic:
Electrical measurements
the 2nd. Year
Performance measurement DC, AC 1f
Prepared by: Ing. Jiří Smílek
Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002
je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.
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Work is a physical quantity.
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Power output equals work done in one second.
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◦ Designation – W- el. work (energy) - A –mechanical work
◦ Unit - 1J = 1 W.s (electrical ) joule (symbol J) - other
◦ Designation - P
◦ Unit - watt (symbol W).
Power output equals work done in one second P=W/t (W;Ws,s)
Electrical power output– electrical power current I at a voltage
U
◦ P=U.I
◦ Unit - watt (symbol W).
 Direct current power output- DC
 P=U*I, Unit - W - watt
only active
 Using Ohm’s law I=U/R (U=RI, R=U/I)
 P=RI2
 P=U2/R
 Alternating current power output- AC
 1 f - single-phase
 apparent S=U*I ,
 unit – V.A – volt-ampere
 active
P=U*I*cos φ,
 unit - W - watt
 idle
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Q=U*I*sin φ,
unit - var – volt-ampere

reactive
 3
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f - three-phase
apparent S=√3U*I
active
P=√3U U*I*cos φ
idle
Q=√3U U*I*sin φ
 Power output P – common name
 Power appliances P1 – power output, which
the appliance consumes – the motor
voltage and current
 Power output appliances P2 – power
output, which the appliance puts out –
the motor speed and torque
Power input(100 %)
 Supplied power
 P1 = P2 + ΔP
Power output (85 %)
power put out
P2 = P1 - ΔP
 Loss of power- ΔP=P1-P2 - Unit W
 The engine heat
 Efficiency η=P2/P1 . 100 - Unit %
Power input(100 %)
 Supplied power
 P1 = P2 + ΔP
Power output (85 %)
power put out
P2 = P1 - ΔP
 Loss of power (15 %)
 ΔP = P1 – P2
 DC – direct current power output
 Measurements using the method:
 indirect – voltmeter and ammmeter
 RV – internal
resistance of the
voltmeter
 RA – internal
resistance of the
ammeter
a) I = IA , U = UV – UA = UV - RA . IA
P = U . I = U V . I A - RA . I A 2
RA << R
b) U=UV , I = IA – IV = IA - UV / RV
P = U . I = UV . IA - UV2 / RV
RV >> R
 AC – Alternating current power output
 Measurements using the method :
 direct – wattmeter,
 To check using a voltmeter and ammeter
 With the current coil voltage
 Actual power output Ps
 PS = P – RAI2 – RWAI2
 RWA – coil current resistance meter
 AC – Alternating
 Measurements using the method:
 direct – wattmeter,
 To check using a voltmeter and ammeter
 With the current coil voltage
 Actual power output Ps
 PS = P – U2/ RV – U2RWU
 RWU – coil resistance voltage meter
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Name the types of power output:
a)
b)
c)
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d)
e)
f)
Explain what power input is
◦
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Explain how you prove a loss of power
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Write how to calculate the motor efficiency
◦
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How can you overload:
a) A current coil wattmeter,
b) A voltage coil wattmeter
c) Two coils,
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Even when the hand shows deflection within
the scale?
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Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN
80-7361-269-7.
Wikipedie
Příručka elektrotechnika, Europa 2000
Elektrické měření - E. Viteček, Vl.HOS - SNTL 1978
Elektřina kolem nás – Zdeněk Opava – Albatros 1981
Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013.
Available at: http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-prokonkurenceschopnost