Soft starters for industrial asynchronous motors

Electronic soft starters are the modern answer to the challenges of starting large asynchronous motors. Using the principle of phase control, they specifically reduce the voltage during switch-on and increase it successively up to the full mains voltage. This minimizes dangerous inrush current peaks and protects the power grid as well as the mechanical components.

Since the torque of asynchronous motors decreases quadratically with the voltage, a soft start ideally takes place in a no-load state or with a low load. Modern devices offer decisive advantages here:

• Reduced wear: Reduction of mechanical shocks in gears, belts, and bearings.
• Efficiency: Many devices bypass the electronics after startup using relays or bypass contactors to minimize power loss and heat generation.
• Retrofit: Soft starters today efficiently replace outdated star-delta circuits and offer more precise control with a more compact design.

Soft starter or frequency inverter: Making the right choice

While the soft starter primarily optimizes the start and stop process, a frequency inverter (VFD) offers continuous speed control. The essential difference lies in the torque: a frequency inverter provides high torque even at minimum speeds. This is indispensable for applications under full load, such as compressors that have to start against existing pressure.

Advantages of the frequency inverter compared to the soft starter:

• Variable speed control during the entire operation.
• Targeted braking and controlled stopping of heavy masses.
• Maximum energy savings in pump and fan applications through demand-based control.

Compact soft starters of the SSCi series with integrated motor protection

The SSCi series represents a particularly economical and space-saving solution for modern drive technology. Designed according to international IEC/UL/KC standards, these soft starters combine performance with maximum operational reliability.

Special features of the SSCi series:

• Integrated bypass: Reduces the operating temperature and enables a compact design for DIN rail mounting.
• Intelligent motor protection: The SSCi model permanently monitors the motor current and calculates a thermal image from it. When critical values (105%) are reached, the device trips automatically, often making external protective devices redundant.
• Diagnostic LEDs: Two clearly visible LEDs on the front enable immediate fault diagnosis and minimize downtimes.

Whether for industrial fans, conveyor belts, or machine drives – choosing the right soft start module is crucial for the longevity of your entire system.