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M-4272 Digital Motor Bus Transfer System
closes either as a result of a subsequent movement into the delta phase angle limit within the Fast Transfer Time
Window, a movement through a predicted zero phase coincidence within the Delayed In-Phase Transfer Time
Window, or by a drop in the motor bus voltage below the Residual Voltage Transfer limit, or after the fixed time
delay of the Fixed Time Transfer. Transfer is completed and the new source* breaker is closed by any of the
above methods whose criteria is first satisfied.
Refer to Figure 4 for Timing Sequence of Transfer Logic in Simultaneous Transfer Mode.
Bus VT Fuse-Loss Detection (60FL)
A Bus VT Fuse-Loss condition is detected by comparing either the three-phase voltage of the motor bus to the
three-phase voltage of the connected source (VT's in three-phase connection) or single phase voltage of the
motor bus to a single phase voltages of the connected source (VT's in single phase connection): phase a to
phase a, phase b to phase b, and phase c to phase c.
Auto Trip
If an external operation closes the second breaker while leaving the first one closed, and if the Auto Trip feature
is enabled, there is a breaker trip option: the MBTS will trip the breaker that was originally closed or the breaker
that has just been closed within an adjustable time delay (0 to 50 Cycles in increments of 0.5 Cycle) after the
second breaker is closed. This Auto Trip operates to transfer in either direction. The purpose is to allow external
parallel transfer but prohibits inadvertent parallel operation. It must be noted that the external operation that
closed the second breaker must be supervised by means external to the motor bust transfer system.
Auto Close
If an external operation opens the second breaker while leaving the first one open, and if the Auto Close feature
is selected, the MBTS will close the breaker that was originally opened. The originally opened breaker will be
closed using the Fast Transfer, Delayed In Phase Transfer, Residual Voltage Transfer or Fixed Time Transfer
method depending upon the bus voltage decayed condition. This Auto Close operates to transfer in either
direction. The purpose is to permit a transfer when the normally-closed breaker is accidentally/inadvertently
tripped resulting in two open breakers. This operation is very similar to the regular transfer process except it does
not send out the trip command, since the second breaker is already opened.
Lockout/Blocking
A transfer is blocked when any lockout/blocking condition described below is active:
•
Voltage Blocking – If prior to a transfer, the new source* voltage exceeds the Upper or Lower voltage
limits, all transfers are blocked as long as the voltage remains outside these limits.
•
External Blocking – When this control input contact is closed, all transfers are blocked.
•
Incomplete Transfer Lockout – Blocks any transfer initiated by a protective relay initiate or an
automatic initiated transfer or manual transfer if the last transfer has not been completed within the time
delay. A time delay can be set from 50 to 3000 Cycles. The MBTS remains in the lockout condition until
manually reset.
•
Bus VT Fuse Loss Blocking – Transfer is blocked if the Bus VT fuse loss is detected and the customer
has selected to block transfers when this occurs.
•
“Both Breakers Same State” Blocking – If both breaker status contacts are in the open state, due to an
external operation that opens the second breaker while leaving the first one open, and if the Auto Close
feature is not selected, no transfer sequence is initiated. Furthermore, any subsequent initiation of a
transfer sequence while the breakers are in this state is inhibited. Also, if both breaker status contacts
are closed due to an external operation that closes the second breaker while leaving the first one
closed, and if the auto trip feature is disabled, no transfer sequence is initiated.
•
Transfer in Process Blocking – Once a transfer is in process, any other transfer initiate inputs will be
ignored until the original transfer is complete.
•
Blocking After Transfer – After a transfer has been completed, any additional transfers are blocked for
0 to 8160 cycles, as selected by the user.
•
Trip/Close Circuit Open Blocking – Transfer is blocked if the Trip or Close Circuit Open is detected.
•
52a and 52b Position Disagreement Blocking – Transfer is blocked when the 52a and 52b status input
positions disagree (applicable when both 52a and 52b status inputs are used).
* NOTE: The 'new source' is defined as the source to which the bus is being transferred.
Содержание M-4272
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Страница 214: ...Declaration of Conformity Appendix I I 1 IAppendix I Declaration of Conformity ...
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