Automation Direct Stellar SR55 Series, User Manual

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Page B–4 Stellar
®
SR55 Series Soft Starter User Manual – 1st Ed, Rev F – 09/18/2019
Appendix B: Soft Starter Application Considerations
b.1.11 – e
ffiCienCy
Although the use of the soft starter introduces a power loss, the system still retains an overall
efficiency of approximately 99.5%. If the iERS function is selected, then the gain in motor
efficiency at partial loads is far greater than the loss of efficiency arising from thyristor heat
losses. If prolonged operation at full load is expected, the thyristor loss can be eliminated
(as in some matched motor/pump drives) by closing the internal bypass contactor around
the thyristors. (SR55 soft starters have an internal bypass contactor that is automatically
activated when at full load when iERS is turned on.)
b.1.12 – h
igh
-e
ffiCienCy
m
oTors
Due to an inherently steep front to the speed/torque curve, high-efficiency motors can exhibit
instability when lightly loaded, and the iERS parameter group may need to be adjusted to
compensate.
b.1.13 – eu C
omplianCe WiTh The
emC d
ireCTive
When considering the use or fitting of any Soft Starter, users and installers in European
countries must comply with the EMC Directive 2004/108/EC. The manufacturer of the soft
starter has a statutory obligation to provide a guide for compliance with this directive.
For the SR55, this guidance is given in the EMC guide, which is Appendix C of this user
manual. It is essential that users and installers understand and comply with the requirements
described in these sections.
b.1.14 – f
uses
Circuit protection fuses should be rated to allow for the extended start times associated with
the use of a Soft Starter. Traditional HRC motor fuses may need to be rated higher than the
motor rated current for normal low-inertia applications, but modern “extended start” fuses
will generally give full motor protection. (See also section B.2.2 relating to high inertia loads.)
Semiconductor fuses are available for the short-circuit protection of the thyristors in the
SR55. See the “Fuse and Current Ratings” section in chapter 2 (“Electrical Installation”) of this
manual for semiconductor fuse recommendations and details of the Overload incorporated
into the SR55.