2. Tutorial: Mechanic - electrician Topic: Electric measurement the 2nd. Year Measuring devices 3 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.

3.  Types of system ◦ Resonance  Uses  frequency measurement - especially industrial frequency ◦ Inductance  Uses  measurement of electricity  1 Phase  3 Phase  active  reactive

4.  The system of resonance Construction: The measuring system comprises: an electromagnet, yoke steel springs (tongues), tuned to the mechanical resonance vibrations of certain frequencies of measured currents.

5.  Principle of operation:  the most vibrated tongue, whose own mechanical frequency is in resonance with the frequency strength, which vibrated the tongue – ie double the frequency of the current coils  Describe the function:  tongues are put into electromechanical resonance alternating magnetic field to excite immobile coils.

6.  Properties: Measured frequency 16 – 1500 Hz Accuracy to 0,2 % (currently 0,5%) Need to observe the approximate nominal voltage Dependence on temperature - change in flexibility of tongues vibration pads  Uses: Measurement of industrial frequencies (50 Hz) Tachometers, with a narrow speed range Symbol:

7.  Induction system – with a gradual field Construction: 2 electromagnets small air gap voltage coil a lot of thread, thin wire large air gap current coil few turns, strong wire aluminium wheel, revolution counter  Properties: Large overload, large private consumption, low accuracy, a large influence of temperature and frequency. measures only AC electrical energy. Symbol:

8.  Principle of operation:  currents in the electromagnet coils are phase shifted  influence of spatial distribution of nuclei produces a gradual magnetic field.  This field raises in the wheel eddy currents that cause torque  Principle function:  the measurement of energy consumption is a current coil associated with a network in series with the appliance, ◦ in a 3 phase meter there are 3 current coils  voltage coil is connected to the network in parallel  counter records the consumption of electrical energy  usually in kilowatt-hours - kWh

9.  Name the known measuring systems ◦  Describe the design of some of the systems  Describe principle functions 1. system  Draw a symbol of the measuring device 1. system  Name the uses of the system 1. system

10.  Fill in the missing words :  currents in the coils of the electromagnet are …………………….. …………………….  influence ……………… ………………cores produces ………………. magnetic field.  the field raises in the wheel……….. ……….., that ……….. torque.

11.  Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN 80-7361-269-7.  Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013.  Dostupné na: http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro- konkurenceschopnosthttp://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro- konkurenceschopnost  Učebnice Elektrická měření – Ing. Pavel Vylegala, SŠE Ostrava, 2006  Učebnice Elektrické měření – SNTL, 1981