T&R PCU2 mk5, Operating And Maintenance Manual

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2.4 Timing System
The PCU2 timing system is very flexible, and is closely integrated with the main output. A
summary of the start and stop events for the timer is shown in the table below.
Timer Mode Timer Start Condition Timer Stop Condition
Off - -
Internal Start Main output on Contact set 1 change
Single Contact Contact set 1 change Contact set 1 change
Dual Contact Contact set 1 change Contact set 2 change
Current Operated Current >20% of range Current <20% of range
The timer is reset by pressing the small pushbutton on the front of the timer display. In each
mode that the timer is active, the output of the unit must be switched on to arm the timer.
Contact set 1 has a contact input for volt-free contacts and a Vdc input for dc voltages. The
Vdc input may be used to trigger the timer from a dc voltage, and will trigger from either the
voltage switching from zero to 24-240Vdc or 24-240Vdc to zero. The voltage must be
connected with positive to the red “Vdc” terminal and negative to the blue “com” terminal.
Contact set 2 has a volt-free contact input.
2.4.1 Timer Modes
2.4.1.1 Timer Mode: Off
In the ‘off’ mode, the timer has no effect on the operation of the set, and the timer does not
run. This mode is used to set the required current through the test object before a timing test.
2.4.1.2 Timer Mode: Internal Start
The internal start mode starts the timer when the main output is switched on, and stops the
timer on the first change of contact set 1. When the timer is stopped, the output of the unit is
automatically switched off.
2.4.1.3 Timer Mode: Single Contact
In single contact mode, the timer starts on the first change of state of contact set 1 after the
output is switched on, and stops on the second change on contact set 1. The output is
automatically switched off when the timer is started. The timer is reset when the output is
switched on. This timer mode is ideally suited to timing auto-reclose devices.
2.4.1.4 Timer Mode: Dual Contact
Dual contact mode uses both contact set 1 and contact set 2. The timer starts on the first
change of contact set 1 after the output is switched on, and stops on the first change of
contact set 2. The output of the unit is automatically switched off when the timer starts.