MENTOR 12 USER’S MANUAL SECTION 3: ADVANCED CONTROL – Page 74
amount of accuracy in this search, the fixed increase selected should be very small,
which would make the test very long, and not very practical, for this same reason.
The Binary Search function is designed to cover this circumstance, that is, when you do
not know the trip value or even, when you wish to verify a known trip value carrying out
the test in a different way.
An initial search point is defined in this function as well as an end point that may be
separated from the initial one as much as we want (for example, between 0.01 and 25
A) as well as a maximum function Precision or Resolution.
After defining these limits, the function will give a first pulse at half the value of the
range defined by the initial and end values (21 + 10.10 = 31.1 which / 2 = 15.55, in our
example). If it detects a trip it drops to half the difference between the last applied value
and previous value (if this is the first point the previous value would be the starting
level). If it does not detect a trip it increases to half the difference that it dropped
previously (If it is the first pulse then this would be the upper limit)….and so on and so
forth, until the value of the increase to be reduced is the same or less than the value
entered in the resolution box. This is a very quick and accurate way of searching for trip
values.
The most significant difference, however, between a Binary Search and the previous
Ramps is that only one trip is detected in the Ramps (going up or down until this occurs)
whereas in the Binary Search multiple trips occur for the relay tested.
This is not a trivial difference, as the majority of the relays block the output relay in their
active mode if a trip occurs and do not reset again until they detect that the switch is
unquestionably open.
This behaviour obviously represents a problem when the test comprises multiple trips.
The state of the switch is analysed either by confirming that the current measured is null
or very close to zero (typically < 100 mA) or detecting that the input corresponding to
52A is open. The 52A is the auxiliary contact of the switch that indicates its position,
which would correspond with a binary output in the Mentor if the power switch is being
simulated. Some relays even need to confirm both circumstances before resetting the
trip contact.
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