T&R PCU2 mk5, Руководство по эксплуатации и техническому обслуживанию

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2.4.1.5 Timer Mode: Current Operated
Current operated mode is used to time devices that have contacts in series with the current
sense element. This includes many types of circuit breakers and trips.
The timer is started when the output current exceeds 20% of full scale of the selected
metering range, and stops when the current falls below this threshold.
2.4.2 General Procedure for Timing Tests
2.4.2.1 Connections
Ensure that the unit is switched off and the test object is isolated and grounded before making
any connections.
Connect the loading unit to the control unit as shown in figure 2.2.
Select the desired series/parallel output arrangement on the loading unit, and connect the
output cables to the test object. Select the appropriate loading unit series/parallel position on
the PCU2 loading unit connection switch.
Connect the supply lead to the mains and move the supply switch to the on position. The
supply on lamp should now be illuminated.
2.4.2.2 Testing
It is advisable to make a preliminary test on the test object, starting at zero voltage, in order to
test the load impedance, before performing the test with regulator set at higher values.
Therefore, ensure the regulator knob is fully anti-clockwise before switching on.
Ensure the timer mode switch is in the off position, and depress the on push-button. Increase
the current by rotating the output control knob in a clockwise direction until the desired current
is indicated on the ammeter. Press the output off push-button.
Connect the test object contacts to the contact terminals on the test set, select the internal
start timer mode, and reset the timer if necessary. If the test object has no auxiliary contacts
(e.g. thermal breakers), it will be necessary to use the current operated timer mode.
When the output on pushbutton is pressed, the following will occur:
a. The timer will start and current will flow through the test object.
b. When the test object's contacts change state the timer will stop and the test current
will be automatically switched off.
c. 2 seconds must now elapse before the timer function is active and ready for a repeat
test.
It is usual to repeat a test several times, checking that the times are consistent. However, it is
advisable to allow the device under test to cool between tests particularly if the test is being
carried out at large over-current factors.
2.4.2.3 After Testing
On completion of the test, return the regulator to zero and switch off the supply. Before
disconnecting the test object ensure the mains supply switch is in the OFF position.