IEC 60034-29 pdf download Rotating electrical machines – Part 29: Equivalent loading and superposition techniques – Indirect testing to determine temperature rise
4 General test requirements
Measurement of the electrical parameters shall be made as follows.
a) The class of accuracy of measuring instruments shall be not greater than 0,5.
b) The measuring range of analogue instruments shall be chosen with a view to the measured values being higher than 30 % of the full-scale range. These requirements need not be complied with in the case of the three-phase power measurement by means of two wattmeters, but the currents and voltages in the measured circuits shall be at least 20 % of the rated currents and voltages of the wattmeters being used. The range of the other measuring instruments shall be chosen in such a way that the measuring errors are not increased.
c) The waveform and symmetry of the supply voltage at the machine terminals shall be in accordance with the requirements of Clause 7 of IEC 60034-1 .
d) Each line current shall be measured. The arithmetic average value shall be used to determine the machine operating point. NOTE When using the two-wattmeter method, it is acceptable to measure only two currents.
e) Power input to a three-phase machine shall be measured by either two single-phase wattmeters connected as in the two-wattmeter method, or one polyphase wattmeter, or three single-phase wattmeters.
The total power read on a wattmeter shall be reduced by the amount of the I 2 R loss in the voltage circuits or in the current circuits of the instruments in accordance with their connection whenever this loss is a measurable portion of the total power. Unless otherwise indicated all electrical quantities to be measured are root-mean-square values.
5 5.1 Superposition method Basic principles
5.1.1 General Superposition tests may be applied to any d.c. or a.c. machine. The method comprises a series of tests at operating conditions other than rated load, for example: reduced load, no load, short circuit, reduced voltage, positive (inductive) or negative (capacitive) reactive load.
The method allows the full-load temperature rise of various component parts of the machine to be deduced. For each component, the loss shall be known at each particular test condition and at full load. The machine should be tested with the same cooling conditions as when operating at rated load. Hence, a locked-rotor test will not be suitable as the air-flow distribution and magnitudes will be incorrect.
On completion of the individual tests, a series of equations based on equivalent thermal circuit theory is constructed, each equation being of the form: 1 m = K 1 1 P 1m + K 1 2 P 2m + K 1 3 P 3m