Automationdirect.com Stellar SR44, User Manual

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3–5
3.2 – Rules for Specific Applications
3.2.1 – In-Delta Operation
The SR44 control system allows the soft starter to be installed “in the delta” connections of the
motor, which can permit the use of a lower current rated unit. However, in this mode of operation
it is important that the soft starter is connected in accordance with the relevant wiring diagram.
The connection diagram in Figure 2.3.2 of the Electrical Installation chapter gives detailed
instructions for this configuration. If motor rotation is incorrect, the connections should be
changed as detailed in Figure 2.3.2. It should be noted that six connections are required between
the motor and soft starter. Parameter P6 must be set to 1 for delta mode, which also disables
optimizing.
An in-line isolation contactor controlled by the soft starter MUST be used with the In-
Delta Firing Mode and motor connections.
3.2.2 – High-Inertia Loads
High-inertia loads, such as centrifugal and axial fans, grinders, flywheel presses, etc., may require
a larger size soft starter than the motor. For example, a 75kW [100 hp] starter may be needed for
a 55kW [75 hp] motor. This is necessary to allow for the extra heating effects of the prolonged
over-current on the soft starter thyristors during the extended starting time. If very high-inertia
loads are involved, then an analysis of the starting characteristics should be made. This requires
accurate data about the motor and the load:
• Complete motor data: Current, Voltage, Power, Speed, Rotor Inertia, Speed/Torque/Current curves
• Complete load data: Type of load, Speed, Inertia, Speed/Torque curve, Power absorbed or Full-load
Torque
Consideration must also be given to thermal overload and fuse protection systems when extended
start times are involved. This is the case for heavy duty starting, as a standard thermal overload
will trip under these conditions. A heavy-duty start thermal overload or an electronic overload
with dual settings for start and run is recommended. Modern HRC motor fuses will allow for some
overload during the start, but the fuse curve, giving time/current data, will give an indication of
suitability for the particular application.
3.2.3 – Reserved
3.2.4 – Resistive Loads
AutomationDirect does not support the control of resistive loads with the SR44 Soft Starter.
3.2.5 – Frequent Starting
High starting frequencies require careful consideration of the soft starter thermal capabilities. In
many cases a standard sized SR44 may be suitable, as start times are generally shorter for this type
of application. If this is not the case, then a larger soft starter may be required.
3.2.6 – Optimizing
Drives which operate for long periods of time at less than their rated capacity can benefit from the
energy saving function (optimizing) of the SR44, which adjusts the thyristor triggering to reduce the
excitation losses of the motor. This feature will lower the running temperature of the machine and
help to extend its life. See Section 3.4, Principles of the Optimizing Mode.
Chapter 3: Applications
SR44 Series Soft Starter User Manual
1st Ed, Rev B 07/31/2019