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Digistart IS User Guide
37
Issue: 4
www.controltechniques.com
7.
Operation
7.1
Start, stop and reset commands
The soft starter can be controlled in three ways:
using the buttons on the keypad
via remote inputs
via a serial communication link
The
LCL/RMT
button controls whether the Digistart IS will respond to local control (via the keypad) or remote control (via the remote
inputs).
The Local LED on the keypad is on when the soft starter is in local control mode and off when the soft starter is in remote
control mode.
The Remote LED on the Digistart IS is on when the soft starter is in Remote mode and off when in Local mode. The
Remote LED is located on the main body of the starter (behind the keypad) and is only visible if the keypad is remotely
mounted.
Control via the serial communication network is always enabled in local control mode, and can be enabled or disabled in remote
control mode (see Pr
3O
). Control via the serial communication network requires an optional communication module.
The
STOP
button on the keypad is always enabled.
To reset a trip on the soft starter, press the
RESET
button on the keypad or activate the Reset remote input.
NOTE
Adaptive Control, Jog, Brake and PowerThrough functions are not supported with inside delta (six-wire) operation. See
Inside Delta Operation
on page 43
7.2
Soft start methods
Soft starters offer a variety of methods to control motor starting. Each soft start method uses a different primary control parameter.
Table 7-1 Soft start methods
Soft Start Method
Parameter Controlled
Performance Parameters Influenced
Timed Voltage Ramp
Voltage
Start current, start torque, acceleration
Constant Current
Current
Start torque, acceleration
Torque Control
Torque
Start current, acceleration
Adaptive Control
Acceleration
Start current, start torque
Best results are obtained by selecting the soft start method that directly controls the parameter of most importance for the
application. Typically soft starters are used to limit motor start current or control load acceleration and/or deceleration.
The Digistart IS offers Constant Current or Adaptive Control. Use Pr
2A
to select the soft start method.
Table 7-2 Control functions of soft start methods
To Control
Use
Motor Start Current
Constant Current
Motor/Load Acceleration
Adaptive Control
To soft start the motor, press the
START
button on the keypad or activate the Start remote input. The motor will start using the start
mode selected in Pr
2A
.
7.2.1
Constant current
Constant current is the traditional form of soft starting, which raises the current from zero to a specified level and keeps the current
stable at that level until the motor has accelerated.
Constant current starting is ideal for applications where the start current must be kept below a particular level.
Figure 7-1 Constant current soft start
C
ur
re
nt
(%
mot
or
fu
ll
loa
d
cu
rre
nt
)
700%
600%
500%
300%
100%
400%
200%
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
1
3
2
1: Initial current (Pr
2C
)
2: Current limit (Pr
2B
)
3: Full voltage current
Rotor speed (% full speed)
