Characteristics - Applications Calculations

1 Isolated Current andVoltage TransducersCharacteristics - ApplicationsCalculations2 The LEM Group today provides multidisciplinary know-howand solutions for power electronic measurements and tasksin key economic segments like Energy, Transportation,Industry, R&D, Engineering, Medical, Environment, TestFacilities, total commitment to the quality of our products andservices is a priority. Together with the best combination ofunderstanding and competence, is this the only way to gaincustomer confidence and to guarantee long term Current and Voltage TransducersCharacteristics - Applications - CalculationsSummaryPage1 Optimal solutions with 5 differentLEM transducer technologies42 Determining parameters fortransducer parameters need to be selection selection criteria53 hall effect to the hall loop current and principle of and Typical of the measurement loop current and principle of and Typical of calculation and of the

2 Measurement power loop voltage and principle of transducer without incorporatedresistor transducer with incorporatedresistor Typical applications174 Closed loop transducers, C and principle of and CT current CD differential current CV voltage CT current CD differential current CV voltage of the measurement CT current CV voltage transducers205 Closed loop transducers, IT and principle of of the measurement accuracy22 Isolated Current and Voltage TransducersCharacteristics - Applications - CalculationsPublished byLEM Coporate Communications LEM Geneva, Switzerland 1996 All rights are reservedPrinted on non-polluting brochure has been written together by several employees.

3 R diger B rkel, Michel Friot, Hartmut Graffert, Hans-DieterHuber, J rgen Ko , Andreas Nemitz, Alfred to change design or specifications are for protection against supply polarity dv/dt disturbances237 LEM-flex - the flexibleAC current and principle of and of the measurement accuracy258 Current and principle of and of the measurement accuracy279 Glossary A - Z28-2910 Design specification, questionnaire31 LEM International Sales Representatives3241 Optimal solutions with 5 different technologies of LEM transducersDuring its 25 years of existence (1972-1997), LEM has beenable to respond to a number of specific demands, thuscreating a wide range of galvanically isolated current andvoltage transducers, which have become standards in themeasurement field and the Characteristics of which areclearly shown in the catalogue.

4 The user may select fromnumerous models divided into 5 main groups for themeasurement of current and voltage (Table 1):- Open-loop hall effect transducers- Closed-loop hall effect transducers- C-type closed-loop transducers- IT-type closed-loop transducers- LEM-flex, flexible transducers for AC summary table hereafter and the detailed description ofthe typical Characteristics of these technologies, make iteasier to choose the most suitable transducer for though most of the Applications will find their bestsolution with a standard transducer selected out of one ofthe 5 technologies mentioned.

5 Please contact your LEMspecialist if your needs are not totally met. He will thenpropose a transducer, specific for your solutions with 5 different technologies of LEM transducersCurrent measurementHall effectHall effectC-typeIT-typeLEM-flex, flexibleopen loopclosed loopclosed loopclosed looptransducerstransducerstransducerstra nsducerstransducersfor AC currentMeasuring rangeIP0 - 18000 A0 - 15000 A0 - 150 A0 - 600 A0 - 60000 ABandwidthf0 - 25 kHz0 - 200 kHz0 - 250/500 kHz0 - 100 kHz8 Hz - 100 kHzTyp. accuracyat 25 CX 1 % % %2 ppm 1 %Linearity % % %1 ppm %Response timetr<3 - 7 s<1 s<50 sOperatingtemperatureTA-25 - +70 C-40 - +85 C-25 - +70 C-10 - +50 C-20 - +85 CTable 1.

6 Overview of the various LEM transducer technologies with their corresponding main characteristicsVoltage measurementHall effectC-typeclosed loopclosed looptransducerstransducersMeasuring rangeVP0 - 9500 V0 - 7000 VBandwidthfseveral kHz0 - 400/700 kHzTyp. accuracyat 25 CX 1 % %Linearity 1 % %Response s0,6 sOperatingtemperatureTA-25 - +70 C-25 - +70 C5 Determining parameters for transducer selection2 Determining parameters for transducer selectionThe wide variety of the LEM transducer range is the directresult of our know-how and many years of experience.

7 Thisenables us to respond to the specific problems of ourcustomers within the greatly diversified application fields ofpower parameters need to be considered?The selection of a transducer is linked to parameters whichare both technical as well as aspects of an application must therefore be globallyenvisioned and taken into account. Among the technicalparameters the following must be mentioned in particular:- The electrical constraints- The mechanical constraints- The thermal constraints- The environmental conditionsIn the development phase of a product, when it has to becharacterised, each parameter is tested, usually individually,without being combined with several others.

8 As regardsproduction control, a quality plan is set up, which indicatesthe tests to be carried out on each product so as to check itscompliance. These tests, which are termed routine tests,are, unless otherwise specified, generally carried out at no-minal current and within a laboratory environment, the practical application is considered, it often is thecase of a combination of several factors which must beevaluated in their totality, so as to select the example, the current to be measured is not the nominalcurrent, the environment combines with magnetic, thermaland mechanical constraints, there are phenomena oftransient overloads.

9 Thus an assembly of parameterswhich may influence the correct operation and the quality ofthe selection criteriaFor a simple application, namely in an environment whichcan be qualified as "clean", electrically, climatically andmechanically, one must first of all refer to the generalcatalogue of LEM transducers, which shows the variousranges of available products with their main Characteristics intabular form. The individual data sheet of each product willthen inform you in greater detail of its following parameters will guide you to a first sample ofproducts which, among the various existing technologies,may prove satisfactory for selection criteriaFor an application of higher complexity, involving acombination of various environmental elements, such as:- Disturbed magnetic environment;- Electro-magnetic interference;- Fast transitory fronts generating important common modevoltage variations (dv/dt).

10 - Disturbances of mechanical origin (vibrations, shocks, )- Specific requests relative to a desired level of partialdischarges;- Compliance with specific standards;- information may be necessary to carry out yourdefinitive is therefore generally useful to supply us with a set-updiagram of your installation and the most detailed possibledescription of the operating conditions of your application ( graph of the waveform of the signal to be measured,nearby disturbing elements such as inductances, othercurrent carrying conductors, or other environmentalconditions).