7
4.7 Short Time (ST) Pick-Up Test
To test the ST pick-up:
1) Hold down the Current Preset while
adjusting the Amp Coarse and Fine pots
to 90% of the calculated ST
SPU.
2) Set the Phase selector to either Phase a,
B or C.
3) Push the Start button but leave the test
current on only long enough to see if a
ST trip occurs. If the current is left on
long enough a LT trip will occur.
A ST trip should NOT occur.
4) Hold down the Current Preset while
adjusting the Amp Coarse and Fine pots
to 110% of the calculated ST
SPU.
5) Push the Start button.
A ST trip should occur. The test set
current will stop and the timer will
freeze displaying the trip time.
6) Verify that the AC-PRO saved the
proper last trip data.
7) Repeat for the other two phases if
desired.
4.8 Short Time (ST) Test
To test the ST time delay trip:
1) The first step is to select a test current.
For example, 150% of the ST pick-up.
The desired test current is then 1.5 X
ST
SPU
.
Note, to accurately test the ST delay, the
test current must be at least 110% of the ST
pick-up.
2) Hold down the Current Preset while
adjusting the Amp Coarse and Fine pots
until the display shows the test current
calculated in step 1.
3) Set the Phase selector to either Phase A,
B or C.
4) Push the Clear button to reset the timer
to zero.
5) Push the Start button.
6) When the AC-PRO trips, the test set
current will stop and the timer will
freeze displaying the trip time.
7) Compare the trip time with the TCC
(Figure 4) for the ST time band setting
in the AC-PRO.
8) Verify that the AC-PRO saved the
proper last trip data.
9) Repeat for the other two phases if
desired.
