Operation
Constant Current with Current Ramp
Current ramp soft starting raises the current from a specified starting level (1) to a
maximum limit (3), over an extended period of time (2).
Current ramp starting can be useful for applications where:
• the load can vary between starts (for example a conveyor which may start loaded or
unloaded). Set the initial current (parameter 2C) to a level that will start the motor
with a light load, and the current limit (parameter 2D) to a level that will start the
motor with a heavy load.
• the load breaks away easily, but starting time needs to be extended (for example a
centrifugal pump where pipeline pressure needs to build up slowly).
• the electricity supply is limited (for example a generator set), and a slower
application of load will allow greater time for the supply to respond.
Current (%mo
current)
700%
600%
500%
300%
100%
400%
200%
1
4
3
2
1: Initial Current (parameter 2C)
2: Start Ramp Time (parameter 2B)
3: Current Limit (parameter 2D)
4: Full voltage current
Timed Voltage Ramp
Timed voltage ramp (TVR) soft starting ramps the application of voltage to the motor over a
defined time period. The voltage ramp reduces the initial starting torque and slows the
motor's rate of acceleration.
TVR starting can be useful for applications where multiple motors of different sizes are
connected in parallel, and/or the loads are not mechanically linked.
NOTE
For multiple motors of the same sizes, and/or mechanically coupled loads, use
constant current starting.
NOTE
TVR soft starting is not suitable for high inertia loads (such as fans), which require
a high level of voltage to accelerate the load.
For a timed voltage ramp start, the following are typical values and can be adjusted to suit
your specific application:
• Add the FLC value of all the connected motors. Use this combined value to set
parameter 1B Motor Full Load Current. (Note that the combined value must not
exceed the starter rating.)
• Set parameter 2C Initial Current to 100%, parameter 2D Current Limit to 500%, and
set the ramp time as required (parameter 2B Start Ramp Time).
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