T&R 228-1, Operating And Maintenance Manual, Page: 35 / 56

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Loading unit Metering range Range full scale
Approximate timer
start/stop current
Secondary
Injection from
CU-Ps
10A 10A 2A
20A 20A 4A
100A 100A 20A
PLU-5k
Parallel Mode
10% 500A 100A
50% 2500A 500A
100% 5000A 1000A
PLU-5k
Series Mode
10% 250A 50A
50% 1250A 250A
100% 2500A 500A
PLU-6k
Parallel Mode
10% 600A 120A
50% 3000A 600A
100% 6000A 1200A
PLU-6k
Series Mode
10% 300A 60A
50% 1500A 300A
100% 3000A 600A
2.3.1.6 Pulse Mode
‘Pulse’ mode may be used to generate high current pulses into the test object. The electronic
trips are set to double the normal trip current in the 0.2s, 0.5s and 1s pulse modes. In the 2s
pulse mode, the trips function as normal. This is useful for setting the current when testing
thermal devices and testing instantaneous trips.
2.3.2 General Procedure for Timing Tests
The procedure for timing is the same whether an external loading unit is connected or the
secondary current injection output from the CU-Ps is used.
2.3.2.1 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 2.1. In the case of the
secondary injection output, make the connections shown in figure 2.2.