Transcript SYNCHRONISATION-CHANNEL SELECTION IN POWER …

Power Quality &
Synchronisation
Ben Kemink
Power Quality
What is the Quality of the Power
Measurement?
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Subjects Covered
1. Definition of Electrical Power
2. The meaning of “T”
3. Should we select the Voltage or the Current input
channel for Synchronization?
4. Is an Observation Time an alternative for “T”?
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Power Quality
Before discussing quality of power,
lets have a look at how do we
define
the measurement of electrical power?
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Traditional
 Applied Voltage : u(t) = Upk.sin(t)
 Resulting Current : i(t) = pk.sin(t+)
Amplitude=UrmsxIrms
 p(t) = u(t) . i(t) =
= ½ . Upk . Ipk . cos( ) - ½ . Upk . Ipk . cos(2t+ )
CONSTANT
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AVERAGE=0
Definition of Average Power
P
average

1
T
 p(t ). dt
T0
The most difficult task for the power
meter is to find the period time T
correctly!
Especially with distorted signals this can
be very difficult.
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Traditional 50Hz
Vpk
Tu
Ipk
Ti
Pavg
Tp
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Amplitude=Urms x Irms
Zero Crossing?
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Δt = resolution of Tperiod
The zero crossing lasts at least for one acquisition interval. An
uncertainty caused by time resolution.
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Current input channel is used for synchronization.
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What if the period is longer than the acquisition memory of the
power meter?
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A too low Display Update Rate will not detect changes of short
duration despite a high acquisition speed.
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Power Quality is first of all related to an accurate Power Measurement
Factors that influence the total error for power are:
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Amplitude
Frequency of the fundamental of the input signal
Crest Factor of the input signal (BW)
Crest Factor setting of the Power Meter
Power Factor
Temperature
Use of filters
Acquisition interval
Acquisition Clock Stability
 Correct
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Detection of Period Time “T”
There is enough energy. The challenge is how to control it!
 For Example:
If of 1 gram uranium all atoms split, the heat developed
(energy) can make a water basin, 6 x 6 x 5 meter filled
with water of 0 degrees Celsius, boil.
Source: Van Barnsteen naar Kernchemie,
Dr. K.K. Darrow
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Three ways to control Electrical Power
1. The current is manipulated.
Example:
Switched Power Supplies, Resistors.
2. The
voltage
is manipulated.
Example:
Pulse Width Modulated Power Inverters, Frequency Converters,
Soft-starters, Thyristor Controlled Power Supplies,
Inductive Cooking.
3.
Both
the voltage and the current
Example:
Electronic Ballasts for Lighting
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are manipulated.
1. Current Manipulation
Example: Switching Power Supply
Voltage
Current
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1. Current Manipulation
example: Switching Power Supply, Voltage, Current & Power Harmonics
Voltage
Current
Power
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2. Voltage Manipulation
example: Inductive Cooking
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2. Voltage Manipulation
example: 3-Phase Frequency Inverter Output
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2. Voltage Manipulation
example: Soft starter
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3. Voltage & Current Manipulation
example: Lighting Industry, electronic ballast
WT1600
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3. Voltage & Current Manipulation
example: 50kHz Electronic Ballast for TL
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Summary
 Today electric power consumption is controlled by high
speed (switching) electronics.
 Design engineers are very creative.
 To limit the negative side effects for others, new
regulations are issued frequently to set new guidelines
for design.
 The definition of the average electric power has not
changed, but the selection of the true repetition time T
(period) requires special attention.
 The power meter should allow the user to select the
appropriate synchronisation source for the
measurement calculations.
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The power meter should allow the user to select the synchronisation source for the
measurement calculations.
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THANK YOU
QUESTIONS?
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