Soft Starter VS

What is a Soft Starter?
A Soft Starter is a device used to control the startup current of electric motors. As you may know, the startup current of electric motors is approximately 5 to 8 times the motor’s rated current. This surge, even over a short duration, can cause significant voltage drops (depending on motor size) on the power grid connected to the motor, disrupting protective equipment and other devices on the same network.
Since electric motors often draw high current while accelerating to nominal speed, a Soft Starter can be used to limit the surge—known as inrush current—and control motor torque, resulting in safer, smoother, and gradual startups. Soft Starters protect your electric motor from potential damage and, by reducing heat from frequent start/stop cycles, mechanical stress, and electrodynamic strain on power cables and motor shafts, they extend the lifespan of your motor and the entire system.

Key Features of VS Soft Starters

• Power range: 500KW to 10,000KW
• Operating voltage: 6KV to 10KV
• Control supply voltage: 220 to 240 VAC
• Built-in vacuum bypass contactor
• Digital configuration of the Soft Starter
• Torque and voltage ramp control for start and stop
• Protection during startup and stopping processes
• Electrical protections: phase reversal, overcurrent, undercurrent, current imbalance, overvoltage, undervoltage
• Protection for bypass contactor switch status (on/off)
• MODBUS RTU protocol over RS485 for monitoring and remote control
• Profibus card installation capability
• Easy programming and simple installation

Internal Bypass
Note that the Soft Starter only controls the thyristors during startup and stop phases. Once the motor reaches nominal speed, the Soft Starter no longer affects motor operation and only monitors it.
Therefore, after motor startup, the Soft Starter should be bypassed to reduce wear—especially on thyristors. This process, known as bypassing, significantly reduces internal heat.

Keep in mind that some Soft Starter models do not have built-in bypass. In such cases, an external parallel contactor is used, activated by the Soft Starter once the motor reaches nominal current.