IEC 60051-3:2018 pdf download – Direct acting indicating analogue electrical measuring instruments and their accessories – Part 3: Special requirements for wattmeters and varmete.
5.3.2 Limits of variations See IEC 60051 -1 :201 6. 5.3.3 Conditions for the determination of variations See IEC 60051 -1 :201 6. 5.3.4 Determination of variation due to power factor The power factor shall be lagging for instruments of class indices 0,5 and greater. For instruments of class indices 0,3 and smaller, the test shall be carried out using both lagging and leading power factors. The test shall be carried out with PF = 0. For the recommended test, see IEC 60051 -9. 5.3.5 Special tests for variations Special tests using combinations of the components of the measured quantity may be carried out when considered necessary by agreement between manufacturer and user. 5.4 Operating uncertainty, overall system uncertainty and variations See IEC 60051 -1 :201 6. 5.5 Electrical requirements 5.5.1 Electrical safety requirements See IEC 60051 -1 :201 6. 5.5.2 Self-heating See IEC 60051 -1 :201 6. 5.5.3 Permissible overloads 5.5.3.1 Continuous overload For the recommended test, see IEC 60051 -9.
Wattmeters and varmeters, together with their non-interchangeable accessory (if any), except for instruments fitted with a non-locking switch, shall be subjected to a continuous overload of 1 20 % of the rated values of current and voltage sequentially, the other value being maintained at its rated value. The duration of each application shall be 2 h. After having cooled to the reference temperature, the instrument, together with its non-inter- changeable accessory (if any), shall comply with its accuracy requirements; however, the overload shall not be repeated. The continuous overload test shall be carried out under reference conditions except for current and voltage. The test shall be carried out with PF = 1 . 5.5.3.2 Overloads of short duration 5.5.3.2.1 For the recommended test, see IEC 60051 -9. Wattmeters and varmeters, together with their non-interchangeable accessory (if any), shall be subjected to overloads of short duration.
5.5.3.2.3 The full duration of each overload shall be applied except when an automatic cut- out (fuse) fitted to the instrument has interrupted the circuit in less than the time specified in Table 3. The automatic cut-out shall be reset (or the fuse replaced) before the application of the next overload. 5.5.3.2.4 After having been subjected to the overloads of short duration and after having cooled to the reference temperature, wattmeters and varmeters whose mechanical zero is within the scale, together with their non-interchangeable accessory (if any), shall comply with both of the following requirements: a) the deviation of the index from the zero scale mark, expressed as a percentage of the scale length, shall not exceed the following value: 1 ) 0,5 for instruments of class indices 0,5 and smaller, 2) the class index for instruments of class indices 1 and greater; b) the wattmeter or varmeter, together with its non-interchangeable accessory (if any), after adjustment of the zero (if necessary) shall comply with the accuracy requirements; however, the overloads shall not be repeated. A wattmeter or varmeter whose mechanical zero is outside the scale is considered to have complied with these requirements if, after having cooled to the reference temperature, it has errors not exceeding those relating to its class index; however, the overloads shall not be repeated. 5.5.4 Limiting range of temperature See IEC 60051 -1 :201 6.
5.5.5.1 General For the recommended test, see IEC 60051 -9. If a wattmeter or varmeter has a zero position marked on the scale, it shall be tested for deviation from zero. The test shall be carried out under reference conditions. 5.5.5.2 All circuits energized After a period of energization of 30 s at the upper limit of the measuring range, the deviation of the index from the zero scale mark, expressed as a percentage of the scale length, shall not exceed a value corresponding to 50 % of the class index. 5.5.5.3 Voltage circuit(s) only energized With only the voltage circuit(s) energized, the deviation of the index from the zero scale mark shall not exceed a value corresponding to 1 00 % of the class index. 5.5.6 Electromagnetic compatibility (EMC) See IEC 60051 -1 :201 6. 5.6 Constructional requirements 5.6.1 General constructional requirements See IEC 60051 -1 :201 6. 5.6.2 Damping 5.6.2.1 General See IEC 60051 -1 :201 6. 5.6.2.2 Overshoot See IEC 60051 -1 :201 6. 5.6.2.3 Response time See IEC 60051 -1 :201 6.