GE Industrial Solutions ASTAT BP - Manual (Page 7)

ASTAT BP User Manual
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11.. GENERALITIES
11..11 Squirrel-Cage Motor Starting
There are numerous applications where soft starting and limited current peak are needed, thereby making
direct starting of squirrel-cage motors impossible. Traditionally in such cases other types of starting with
reduced stator voltage have been resorted to. The best-known are star-delta starters, autotransformer
starters, stator resistance starters or using part winding motors.
Any reduced starting voltage imposes a current limitation, thus reducing the starting torque, but there will
always be peaks during the change from one point or state to another which can damage the machine being
driven.
Note that in general, all reduced voltage starts reduce torque in squared proportion to the current in the
phases of the motor (not on the line) and the latter in turn is reduced in linear proportion to the voltage. From
this it can be deduced that any start with reduced voltage reduces the torque in squared proportion to the
voltage per motor phase. From this point of view soft starting produces just like any other reduced voltage
start, a reduction in starting torque, according to the adjusted parameters. The advantage is the ease with
which this ramp can be controlled to produce a soft start in accordance with the actual requirement of the
machine.
11..22 Advantages of the ASTAT-BP Solid State Soft Starters
Increase in productivity and reliability with the use of static
soft starters
Starting and stopping the motor without steps or transitions lengthens the
life of power-driven machine mechanical elements, greatly reducing
stress on transmission and coupling parts.
Consequently, overhauling times are reduced and machine and facility
lifespans are lengthened.
Improvement in acceleration / deceleration characteristics
Being able to start by using the voltage ramp or alternatively by limiting
current lets acceleration fit the load characteristics. Application of a pulse
start may also be selected in cases of high static friction load.
Stopping may be made by cutting-off power or by soft stop ramp.
Internal bypass
In order to reduce heat dissipation and power loss and for better wiring
simplicity, an internal bypass device is incorporated in the ASTAT-BP.
Bypass is closed after ramping up and opens upon stop or soft stop
commands.
Protected motor
The soft starter protects the motor from overloads as well as from
incorrect operating conditions such as loss of an input or output phase,
blocked rotor, thyristor short circuit, etc.
Digital technology
The control system is based on the use of a highly specialized
microcontroller by which signals are treated digitally, thereby avoiding
deratings and adjustments common to analogue circuits and obtaining
excellent precision and speed of execution.
The control board is made with the technology of surface mounting
devices (SMD), which increases equipment reliability.
High level of immunity
Design of the unit was closely tied to the conditions of supply lines, which
handle more disturbances every day. The control signals are
opto-electronically isolated and various levels of protection have been set
up in the circuits to immunize the equipment against external disturbance
and its effects.
Easy to run and adjust
This unit can be used for a wide range of applications.
Adjustments are very easy to make and diverse options maybe selected
for have equipment capabilities suited to application needs every time.
Easy maintenance due to full monitoring
The alphanumeric display and the LEDs on its front overlay makes the
equipment working conditions known at any time.
Pump control
The ASTAT-BP includes several soft stop curves which is more effective
than the standard soft stop, reducing fluid surges or hammering in a pipe
line system. This method reduces the motor speed, by controlling internal
parameters in the motor as well as the output voltage in a close-loop
system.
Advanced functions
The ASTAT-BP includes advanced functions, like linear acceleration ramp,
forward and reverse jog, programmable I/O or connection to a control
system via Modbus protocol included as standard and other optional
protocols.
These functions allow the incorporation of the soft starter to a distributed
control net, in automated plant processes, together with other soft
starters,programmable controllers, variable speed drives, etc.