Fairford synergy, User Manual

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Synergy Series Soft Start User Manual
MAN-SGY-017. Version 01. 27/06/2016
183
8.2.6 Reversing Drives and Plug-braking
Synergy 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. When plug-braking, there should be some form of zero-speed detection to
stop the drive after braking has been completed, otherwise the drive may either accelerate the motor in the
reverse direction or switch off before zero speed has been reached. See section 2.4.4 and figure 2.4.6 of the
Electrical Installation manual for details.
8.2.7 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.
8.2.8 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.
8.2.9 Multiple Motor Starting
See section 2.8.3 of the Electrical Installation manual for details.
8.2.10 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.
8. Applications (continued)