AS NZS IEC 60947.5.9:2015 pdf download.Low-voltage switchgear and controlgear Part 5.9: Control circuit devices and switching elements——Flow rate switches.
8.3.3.2.2 Time delay before availability
The test is performed with the flow rate switch connected to a test circuit shown in Figure 3.
The medium is put in a state such that the switching element is first in the ON-state and then in the OFF-state. With rated operational voltage Ue, or with the minimum value of the rated operational voltage when it is given as a range, the load is adjusted to obtain the minimum operational current ‘m
The time delay before availability and the duration of any false signal are measured by recording the signal across the load with an oscilloscope as the bounce-free “Switch” is closed. Figure 4 shows typical oscillog rams for a d.c. switching element. Figure 4a shows the oscillogram when the switching element is in the ON-state and Figure 4b shows the oscillogram when the switching element is in the OFF-state.
The medium is adjusted to a state 200 % above the set point or 66 % below the set point minus hysteresis.
The measured time delay before availability, the time between t3 and t0 in Figure 4, shall be according to 7.2.1.6. The duration of the false signal, if any, the time between t2 and t, in Figures 4a and 4b, shall be according to 7.2.1.6.
8.3.3.2.3 Minimum operational current Urn)
The test is performed with the flow rate switch connected to a test circuit as shown in Figure 5.
The medium is put in a state such that the switching element is in the ON-state. With supply voltage Ue and the switch S being open, the load R1 is adjusted to obtain the current ‘m The measured value shall not exceed the value specified in 7.2.1.10. The switching element shall not change state during the test.
8.3.3.2.4 OFF-state current (Ir)
With the circuit as in Figure 5 and the switch S closed, the load R2 is adjusted to obtain the rated operational current ‘e when the supply voltage is the highest U0. The medium is then put in a state such that the switching element is in the OFF-state.
The current ‘r shall be measured with supply voltage Ue +10 % or with the maximum value of the supply voltage UB where it is specified as a range. The current ‘r shall not exceed the value specified in 7.2.1.11.
8.3.3.2.5 Independent (snap) action
Independent (snap) action shall be checked at maximum and minimum operating load currents at both maximum and minimum rated operating voltages. Resistive loads of appropriate value shall be used for each of the four tests.
These tests shall be carried out by changing the flow rate of the medium from a state where the switching element is in the OFF-state to a state where the switching element is in the ONstate and observing the output on an oscilloscope. The switching element function shall be substantially independent from the velocity of the change and the output shall switch between the ON and the OFF states without oscillating, or holding at any intermediate level.
8.3.4 Performance under short-circuit current conditions
8.3.4.1 Test circuit and test procedure
The flow rate switch (EUT) in new condition shall be mounted as in service, in free air, and
connected to the test circuit with the same size wire as used in service, see Figure 6.
The short-circuit protective device (SCPD) shall be of the type and rating stated by the manufacturer. This SCPD shall be omitted if the flow rate switch is integrally protected against short-circuits.
The medium is put in a state such that the switching element is in the ON-state, R1 is selected so that the current flowing through the flow rate switch is equal to its rated operational current. The supply S shall be adjusted to 100 A prospective short-circuit current. The SC switch, parallel with R1 load, is intended to cause the short-circuit. The open-circuit voltage shall be 1,1 times the rated operational voltage or the maximum value of the voltage range.AS NZS IEC 60947.5.9 pdf download.

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