99
agility
TM
Series Soft Start User Manual
MAN-AGY-001. Version 04. 21/09/2018
EU Compliance with the EMC Directive
When considering the use or fitting of any Soft Starter, users and installers in European
countries must comply with the EMC Directive 89/336/EEC. The manufacturer of the soft starter
has a statutory obligation to provide a guide for compliance with this directive. For agility
TM
, this
guidance is given in the EMC guide which is A3 of this manual. It is essential that users and
installers understand and comply with the requirements described in these sections.
Fuses
Circuit protection fuses should be rated at twice the motor rated current for normal low inertia
applications. See also section relating to high inertia loads. Semiconductor fuses are available for
the short circuit protection of the thyristors in agility
TM
. See Electrical Installation section for fuse
recommendations.
Rules for Specific Applications
High Inertia Loads
High inertia loads such as centrifugal and axial fans, grinders, flywheel presses, etc., may require a
larger size of soft-start than the motor. For example, a 75kW starter may be needed for a 55kW
motor. This is necessary due to the extra heat produced by the thyristors due to the extended
start times and/or higher over-currents. If very high inertia loads are involved, then an analysis of
the starting characteristics should be made. This will require accurate data about the motor
speed-torque and speed-current characteristics as well as the load characteristics. For further
information, consult your supplier. Consideration must also be given to thermal overload and
fuse protection systems when extended start times are involved. This must be as 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.
Frequent Starting
High starting frequencies require careful consideration of the soft-start thermal capabilities. In
many cases a standard sized agility
TM
may be suitable as start times are generally shorter for this
type of application. If this is not the case then a larger soft-start may be required. (Please refer to
Fairford for further information.)
Soft-Stopping
Soft-stopping can reduce positive surge pressures in pipelines on shutdown. It is necessary to
make sure that the ramp-down time is long enough to remove the energy from the fluid before
the firing of the thyristors is stopped, otherwise the surge pressure may still be present. Soft-
stopping can also be successfully applied to loads such as conveyer belt systems where sensitive
items such as bottles are being transported.
Reversing Configuration
agility
TM
soft-starters used in conjunction with contactor controlled reversing and plug-braked
motors show considerable benefits to the user by reducing mechanical and electrical stresses,
particularly when utilising the current limited start feature. It is required, with this type of
application, to insert a 150 to 350 millisecond delay between the opening of one contactor and
the closing of the other, to allow any residual flux in the rotor to die away.
Applications (continued)