BECKWITH ELECTRIC M-4272, Instruction Book

Page: 148 / 217

System Setup and Setpoints – 4
4–37
• Sequential — With a transfer initiated,
the command to trip the old source breaker
is sent within 10 ms. Upon confirmation
from the old source breaker status contact
that the old source breaker is open. Within
4ms of receipt of this confirmation, all
three transfer methods, Fast, Delayed In-
Phase Transfer and Residual Voltage
Transfer are enabled to supervise closure
of the new source breaker and the Fixed
Time Transfer is enabled 30 cycles later.
Refer to
Appendix F , Transfer Logic Time
Sequence for Timing Sequence of Transfer
Logic in Sequential Transfer Mode.
Common Settings/Upper-Lower Voltage Limit
New Source
This setting defines the upper and lower voltage
limits of the new source. If the new source voltage
is not within these limits, then a transfer is blocked.
If a transfer is blocked and an initiate transfer signal
is received, the transfer is not started (no trip or
close command is sent to the supply breakers).
This prevents a transfer to a new source that does
not meet the voltage requirements established by
the Upper and Lower Voltage Limits. The result is
that the motor bus will lose power when the protective
MBTS trips the supply breaker and initiates a transfer
to the new source at the same time. Since the
existing power is being tripped (due to some
abnormality) and the new source is outside of the
setting range, a transfer will not occur and the motor
bus will lose power.
Common Settings/Breaker Closing Time
The Breaker Closing Time setting defines the breaker
closing time (the time period from when the close
command is issued to when the new source breaker
status contact closes) of the Source 1 and Source
2 breakers that the MBTS is controlling. The breaker
closing time is used during an In-phase transfer.
The in-phase transfer sends the close command in
advance of the phase coinsidence based on this
breaker time and the rate of change of the frequency
of the decaying motor bus.
The purpose of using the breaker closing time is to
have the breaker actually close just at the time of
the phase coinsidence setting is in cycles, so time
changes based on frequency. The Adaptation
feature, when selected calculates the S1 and S2
breaker closing times based on the average time of
the Last 8 breaker operations. When initially selected,
the selected breaker closing time will be used until
eight breaker operations have been averaged.
Breaker Closing Time setpoints cannot be changed
while this feature is enabled.
Common Settings/S1(S2) Breaker Closing
Time Deviation
The S1(S2) Breaker Closing Time Deviation setting
establishes when the breaker has exceeded the
normal expected variations, plus or minus from the
programmed closing time.
When the Breaker Closing Time Deviation setting is
exceeded a “S1/S2 Breaker Closing Time Out of
Range” indicator on the System Status section of
the Secondary Metering and Status screen will be
activated. Activation of this indicator would indicate
that the breaker may require maintenance.
Common Settings/S1(S2) Breaker 52a & 52b
Position Disagreement
The S1 Breaker 52a & 52b Position Disagreement
settings define the time the 52a and 52b breaker
status contacts of the same breaker are allowed to
be in the same state before the MBTS responds to
that condition. If the 52a and 52b contacts on the
same breaker are both closed or both open, then
transfers are blocked. The Pickup Time is the time
that both breaker status contacts are either closed
or both open before the unit responds to that
condition. The Pickup Time allows for possible
overlap of the contacts as the breaker changes
position. The Dropout Time Delay is the time period
for the MBTS to consider the breaker status contact
inputs in the same state after they are no longer in
the same state. This setting is only applicable when
both the 52a and 52b breaker status contacts are
connected to the MBTS.
Common Settings/Incomplete Transfer
Lockout Time
The Incomplete Transfer Lockout Time setting
establishes the time period in which an Automatic
Transfer must be completed. The time period is
defined as the time at which the transfer is initiated
until the transfer is complete.