Soft Starters

General information

When designing applications driven by electric motors, you should always consider what happens when you start and stop the motor. Unsuitable configurations can result in reduced product lifetime or even complete system malfunction. Besides direct on line (DOL), Star/Delta starters and the use of variable frequency drives, another typical starting method is to use a soft starter.

A soft starter works by gradually increasing the voltage to the motor which allows a more smooth and soft start. When reversing the process and gradually reducing the voltage a more controlled stop is ensured. The main advantages of using a soft starter are better application control and the prevention of power spikes.
As your one point of contact Hoyer Drives & Controls offer combined soft starter and electric motor solutions based on the Hoyer motor range and the ATS 22 & ATS 48 series from Schneider Electric.

Choosing a soft starter depends on the following criteria:

• Application type and load
• Nominal power and current of the motor
• Supply voltage conditions and locations
• The frequency of starts and stop in a given period

Product information

ATS 22

• Mainly for industry applications
• Motor power from 4 – 400 kW
• Voltage supply from 3 x 208 to 600V 50/60 Hz
• Integrated bypass contactor in the starter as standard
• Integrated display for easy programming
• Integrated thermal motor protection

ATS 48

• For marine and industry applications
• Motor power from 4 – 900 kW
• Voltage supply from 3 x 208 – 690V 50/60 Hz
• Wide range of marine approvals
• Integrated display for easy programming
• Integrated thermal motor protection

Hoyer can also offer line contactors and bypass contactors together with the soft starters.

Application benefits

Pumps

For pump applications such as centrifugal pumps a soft starter is often used to reduce motor torque during the start sequence. However, a soft stop by slowly decreasing the current is also an effective way of preventing water hammering which can cause wear and tear on the piping.
Soft starters are used for a wide range of marine pump applications, including ballast water pumps, cargo pumps, and scrubber pumps. They are frequently used for cargo pumps, which require soft start and stop, but otherwise operate at full speed.

Fans and ventilation

For centrifugal fans soft starters are often used to reduce the starting torque to prevent belt slipping and prevent voltage drops due to high inrush currents. A significant number of large fans are driven by powerful motors mounted with flywheels which require a heavy duty start. On these applications a soft starter can support a smooth start and stop.

Compressors

A soft starter provides better starting performance for compressors and especially screw compressors where the load torque increases with the speed. It reduces the initial strain on the application and can thereby extend the product lifetime.

Marine market

The ability to eliminate inrush current peaks by using a soft starter is beneficial for generator use and it prevents the generator from overloading and potential malfunction.

Get in touch

Please always contact us for a talk about your specific start and stop requirements.