MIL-PRF-17773C(SH)
6.4.15 Operating transfer time. Operating transfer time is the time measured from the instant of monitored
voltage source deviation to the recognition of an available alternate source, exclusive of any purposely introduced
time delay.
6.4.16 Phase angle difference. Phase angle difference is monitored only if the phase angle difference feature is
enabled. The phase angle difference is measured between the normal and alternate sources.
6.4.17 Pick-up voltage. The pickup voltage of a device is the minimum voltage at which the device starts to
operate. Pick-up voltage is the lowest voltage of a power source at which the ABT will consider that source
available, provided the other monitored parameters are specified and are also within their acceptable ranges.
6.4.18 Preferred source. The source to which the SABT will automatically re-transfer the load in the event
both power sources become available. Either normal or alternate source can be selected to be preferred. If the re-
transfer feature is not active, however, the term effectively has no meaning. When a source is selected as preferred,
it will be so indicated on the front panel.
6.4.19 Re-transfer. The automatic switching of loads from the non-preferred to the preferred source after a
transfer has occurred earlier and subsequently the preferred source has become available. If the phase angle
difference feature is enabled, the re-transfer is performed only with the sources within the maximum allowed phase
angle difference, otherwise it will occur regardless of phase mismatch between sources. The re-transfer feature can
be disabled, in which case, there is effectively no preferred source; the ABT will not automatically re-transfer loads
after the preferred source has been restored to an available state. An indicator on the front panel is lit if the re-
transfer feature is enabled.
6.4.20 Short-circuit withstandability. Short-circuit withstandability is the ability of the ABT switch switching
mechanism to carry the required short-circuit current without permanent damage for the period of time necessary for
circuit protective devices in the system to clear the fault.
6.4.21 Time delay. Time delay is an intentionally introduced delay in the operation of a bus transfer switch.
6.4.22 Transfer. Transfer is the switching of loads from the active to the inactive source. It is triggered by the
ABT upon sensing that the active source is outside preset transfer limits while the inactive source is available.
6.5 Acronyms.
ABT
Automatic Bus Transfer Switch
CCTD Control Circuit Time Delay
EMI
Electromagnetic Interference
ESD
Electrostatic Discharge
LCTD Line Circuit Time Delay
MBT
Manual Bus Transfer Switch
RMS
Root Mean Square
V&V
Verification and Validation
6.6 Subject term (key word) listing.
ABT
MBT
Switch gear
Switching mechanism
6.7 Changes from previous issue. Marginal notations are not used in this revision to identify changes with
respect to the previous issue due to the extent of the changes.
28
For Parts Inquires submit RFQ to Parts Hangar, Inc.
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business