POWER ELECTRONICS
18
TECHNICAL CHARACTERISTICS
o Bypass vacuum contactor:
After the SS starts the motor, the bypass contactor will close allowing the current flow to the motor
through the bypass contactor placing the SCR in bypass. When the soft starter receives a stop
command, the bypass contactor will open allowing the soft starter to make a soft motor stop.
o Fuses (Optional)
The SS could optionally include input overcurrent protection with fuses. Check the maximum interrupting
to ensure the compatibility with the connection point.
o Ground Fault Monitoring Relay (Optional)
Although the SS integrate as standard a current unbalance protection, it can be equipped with an
optional ground fault monitoring relay that fulfills safety installation requirements.
o User interface
The VS65 SS integrates as standard multiple door push buttons and pilots (Start, Stop, ready ...) and an
alphanumeric display suitable for industrial environments. Additionally, it is available with multiple
communication interfaces and analog and digital I/O.
3.2. Operating Principles
The VS65 has a microcontroller as control nucleus which can start and protect the motor. The CPU is
able to control and trigger the SCR phase degree. The effective voltage applied to the motor is controlled
by controlling the thyristor trigger instant. This way, the torque is smoothly increased until the motor
spinning rated speed is reached after the acceleration ramp.
Figure 3.2 Block diagram example
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