Basler Electric SMC-250 - Manual (Page 4)

overexcitation persists and is not corrected, the
DECS-250 closes the SMC-250 Alarm output
contacts (TB1-64, 65).
Reactive Power (Var) Limiter
The DECS-250 compares the level of motor reactive
power with the user-established var threshold. A var
level outside the established setting initiates var
limiting.
During var limiting, the DECS-250 closes the SMC-
250 General Limiting output contacts (TB1-64, 65).
Setpoint Limiter
Adjustment of the active DECS-250 setpoint to either
the upper or lower limit will result in a General
Limiting annunciation at SMC-250 terminals TB1-64
and 65.
Alarms Function
DECS-250 system parameters, communication links,
protection functions, and remote inputs/outputs are
continuously monitored for alarm conditions. An
active alarm triggers closure of the DECS-250
General Protection output contacts at plate/chassis
terminals TB1-66 and 67.
Communication
The DECS-250 supports simultaneous Modbus™
communication through its copper Ethernet port
(Modbus/TCP) and its RS-485 port (Modbus RTU).
Short-term communication with a PC operating
BESTCOMSPlus
® .
Operating Logic
In the SMC-250, the DECS-250 is preconfigured with
operating logic that is tailored specifically to
synchronous motor applications. If desired, this logic
scheme can be customized by using the logic
programming capabilities of BESTlogic™Plus. The
BESTlogic™Plus chapter of Basler publication
9440300990 provides information about customizing
DECS-250 logic.
Motor Protection System (BE1-11m)
The BE1-11m provides startup coordination and
power factor protection for the motor. The BE1-11m
enhances motor reliability by providing the following
features:
•
Comprehensive protection and control functions
•
Standard, IEC, or custom thermal curves which
adapt to thermal, inertia, and voltage conditions
•
Accurate metering of motor parameters
•
Extensive reporting capabilities: current demand,
watthours, varhours, motor start records, and
motor maintenance data
•
Oscillography capabilities can be used to
evaluate motor characteristics (V curves) and
reduce commissioning time
Information about the BE1-11m can be found in
Basler publication 9424200998 (quick-start guide),
9424200996 (device manual), 9424200997
(communication quick-start guide), and 9424200890
(Modbus communication protocol manual).
Startup Coordination
At system startup, a Start contact input is applied to
the BE1-11m which enables DECS-250 excitation
control and prevents an SMC-250 Alarm output from
being issued during startup before the motor reaches
a nominal operating state.
Protection
The SMC-250 is supplied with the BE1-11m
configured for power factor protection. In a
synchronous motor application, power factor
protection prevents the motor from consuming
excessive reactive power (vars). If the var level is
permitted to escalate, a loss of synchronism can
result. A power factor trip closes the contact of
BE1-11m output 8.
Other BE1-11m protection elements can be enabled
and implemented at the user’s discretion.
Communication
The BE1-11m supports simultaneous Modbus
communication through its copper Ethernet port
(Modbus/TCP) and its RS-485 port (Modbus RTU).
Short-term communication with a PC operating
BESTCOMSPlus
® is possible through the front-panel
USB port.
Operating Logic
As implemented in the SMC-250, the BE1-11m
operating logic is preconfigured for basic protection of
the synchronous motor and annunciation of
preselected motor/SMC-250 conditions. If desired,
the BE1-11m logic scheme can be customized by
using the logic programming capabilities of
BESTlogic™Plus. The BESTlogic™Plus chapter of
Basler publication 9424200996 provides information
about customizing BE1-11m logic.
DC Millivolt Sensing Relay (BE3-74SD)
The BE3-74SD monitors the level of exciter field
current through metering shunt SH1 and functions as
an overexcitation/underexcitation relay. The
adjustable underexcitation setpoint is preset at 20%
of the full-load excitation current rating. The
adjustable overexcitation setpoint is preset at 110%
of the full-load excitation current rating. A time delay
setting of 5 seconds for both setpoints prevents
nuisance tripping during transient disturbances.
When an underexcitation or overexcitation condition
is detected, the BE3-74SD trips and closes the SMC-
250 Alarm output contacts. During motor startup,
BE3-74SD tripping is inhibited by the BE1-11m.
Publication
9494900994
Revision
A
Instructions
Date
10/14
Page
4 of 6