100
agility
TM
Series Soft Start User Manual
MAN-AGY-001. Version 04. 21/09/2018
Replacement of Fluid Couplings
Soft-starters can replace fluid couplings yielding benefits of higher efficiency running and lower
costs to the user. If the coupling is used to magnify the available breakaway torque, it may be
necessary to replace the fitted motor with another of a larger size or one with a high starting
torque characteristic before a soft-start can be employed.
Two-speed Motor Applications
Two speed motors, whether Dahlander connected or with dual windings, can be soft started at
each speed, provided that the start is initiated when the actual motor speed is less than the
synchronous speed for the winding selected. This is particularly important when changing from
high to low speeds.
Overhauling Loads
Certain applications can over-speed the motor as part of normal operation. Power flow is then
from the motor to the supply. It is important that the optimising is disabled during the over-speed
condition and reinserted during normal conditions.
Application Table
The table on the following page shows many common motor applications that suit the agility
TM
soft-starter. It lists typical breakaway torque requirements as a percentage of motor full-load
torque (FLT). For the most satisfactory soft-start in a given application, the motor should have a
full-voltage locked-rotor-torque (LRT) that is at least twice the breakaway torque. (E.g. For a
reciprocating compressor the FLT is normally in the region of 50% motor LRT.) As a general rule,
the higher the motor LRT is above the load breakaway torque, the greater the control over the
starting process.
Applications (continued)
