Functional Description
20 S801+ Soft Starter MN03900002E—November 2012 www.eaton.com
Functional Description
Power
The S801+ Soft Starter controls the voltage applied to a
three-phase induction motor in order to control the starting
torque and provide a smooth starting characteristic. Within
the soft starter are three power poles, each of which
includes a set of anti-parallel SCRs (thyristors) in parallel with
a contact. During a start, the conduction periods of the SCRs
are continuously adjusted to apply a gradually increasing
voltage to the motor, resulting in gradually increasing torque
and a smooth start. As the motor reaches its rated speed,
the power pole contacts are closed, bypassing the SCRs for
the most efficient operation.
Inline Connected Soft Starter
For each start, the length of time the SCRs are conducting
current as well as the magnitude of that current determine
how hot the SCRs will get. Between successive starts the
SCRs must cool down to avoid exceeding their thermal
limits. Appendix C gives the S801+’s application ratings for
various starting conditions. Staying within these specified
limits will aid in avoiding over temperature trips.
Control
There is one (1) 12-position connector and one (1) RJ45
connector on the face of the S801+ soft starter that are used
for control circuit functions:
1. 24 Vdc Control Inputs—Soft Starter Permissive, Start,
Reset, and Auxiliary Relay control functions.
2. Control Interface Module (CIM)—soft starter
communication with a user interface device.
Note: Do not apply 120 Vac to any Terminal Block
Control Input. 120 Vac will permanently destroy the
printed circuit board.
M
3~
2 T1 4 T2 6 T3
1 L1 3 L2 5 L3
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