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Power Quality & Synchronisation Ben Kemink Power Quality What is the Quality of the Power Measurement? QUALITY 2 INNOVATION FORESIGHT 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”? QUALITY 3 INNOVATION FORESIGHT Power Quality Before discussing quality of power, lets have a look at how do we define the measurement of electrical power? QUALITY 4 INNOVATION FORESIGHT 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(2t+ ) CONSTANT QUALITY 5 INNOVATION FORESIGHT 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. QUALITY 6 INNOVATION FORESIGHT Traditional 50Hz Vpk Tu Ipk Ti Pavg Tp QUALITY 7 INNOVATION FORESIGHT Amplitude=Urms x Irms Zero Crossing? QUALITY 8 INNOVATION FORESIGHT Δt = resolution of Tperiod The zero crossing lasts at least for one acquisition interval. An uncertainty caused by time resolution. QUALITY 9 INNOVATION FORESIGHT Current input channel is used for synchronization. QUALITY 10 INNOVATION FORESIGHT What if the period is longer than the acquisition memory of the power meter? QUALITY 11 INNOVATION FORESIGHT A too low Display Update Rate will not detect changes of short duration despite a high acquisition speed. QUALITY 12 INNOVATION FORESIGHT Power Quality is first of all related to an accurate Power Measurement Factors that influence the total error for power are: 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 QUALITY 13 INNOVATION FORESIGHT 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 QUALITY 14 INNOVATION FORESIGHT 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 QUALITY 15 INNOVATION FORESIGHT are manipulated. 1. Current Manipulation Example: Switching Power Supply Voltage Current QUALITY 16 INNOVATION FORESIGHT 1. Current Manipulation example: Switching Power Supply, Voltage, Current & Power Harmonics Voltage Current Power QUALITY 17 INNOVATION FORESIGHT 2. Voltage Manipulation example: Inductive Cooking QUALITY 18 INNOVATION FORESIGHT 2. Voltage Manipulation example: 3-Phase Frequency Inverter Output QUALITY 19 INNOVATION FORESIGHT 2. Voltage Manipulation example: Soft starter QUALITY 20 INNOVATION FORESIGHT 3. Voltage & Current Manipulation example: Lighting Industry, electronic ballast WT1600 QUALITY 21 INNOVATION FORESIGHT 3. Voltage & Current Manipulation example: 50kHz Electronic Ballast for TL QUALITY 22 INNOVATION FORESIGHT 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. QUALITY 23 INNOVATION FORESIGHT The power meter should allow the user to select the synchronisation source for the measurement calculations. QUALITY 24 INNOVATION FORESIGHT THANK YOU QUESTIONS? QUALITY 25 INNOVATION FORESIGHT