• Soft Starters

Soft Starters

Soft Starter
A Soft Starter is used to accelerate, decelerate, and protect three-phase induction motors. Soft starters limit the high inrush currents on motor startup. These solid-state starters incorporate thermal overload electric motor protection.

Soft Starters are Solid State devices that protect motors from inrush currents that occur during start up. Our WEG soft starters are available in two series: SSW07 and SSW06. In addition, we also offer enclosed combination soft starters built-to-order by our panel shop.

  • 17 to 1400 Amps
  • 5 to 1500HP
  • 230, 460, or 570V Models
  • Duty cycle: 300% FLA for 30 seconds, 10 starts per hour (with vent kit)
  • IP20 Finger-safe option
  • Operates in ambient temperatures up to 131ºF (55ºC)
  • Variety of wire ranges and stud hole sizes
  • Built-in electronic thermal relay

What is a Soft Starter?
A reduced voltage soft starter helps protect the motor and connected equipment from damage by controlling the terminal voltage. This limits the initial inrush of current and reduces the mechanical shock associated with motor startup and provides a more gradual ramp up to full speed. Soft Starters are also beneficial to electrical systems with limited current capacity when using a soft starter for motor starting to limit the inrush current. By gradually increasing the motor terminal voltage the soft starter produces a more regulated motor acceleration up to full speed. Soft starters are also capable of providing a gradual ramp to stop where sudden stopping may create problems in the connected equipment.

Benefits of Using Soft Starters
  • Speed ramping and torque control are desired when starting or stopping
  • Limits high inrush currents associated with starting a large motor to avoid supply network issues or penalty charges
  • Strong reduction on mechanical stresses over the coupling and transmission devices (gearboxes, pulleys, gears, conveyors, etc.)
  • Avoiding pressure surges or ‘hammering’ in piping systems when fluid changes speed too rapidly
  • Avoids “water hammer” in pump applications
  • Use chart from SSW07 P4 (Starting Method Comparison)

Operational Functions
Voltage Ramp
Permits smooth acceleration and/or deceleration through voltage ramps.
Current Limit
Enables operator to set current limit during the start according to their application’s requirements.
Voltage Kickstart
Enables an initial voltage pulse which provides starting torque reinforcement. This is necessary for starting high breakaway torque loads.
Built-in Bypass
Minimizes power losses and heat dissipation in the thyristors, providing size reduction and contributing to energy savings.

Solid State
Our soft starters are solid state devices that feature electrical components instead of mechanical components. Solid state devices typically see greater lifespans due to no wear-and-tear from small moving components.

Enclosed Combination Soft Starters
We offer enclosed combination soft starters that include WEG soft starters installed in a wall mount enclosure. These enclosed combination starters also include other devices in the order such as circuit protectors, start/stop pushbuttons, control transformers, and more.

Soft Starters are helpful in extending the life of a system by limiting mechanical shock. They ultimately give you more control over your AC Motors by allowing you to control the ramp up and even ramp down.

Where are Soft Starters Used?
Soft Starters are used in many types of applications due to the control they give operators. Some examples of applications that soft starters are typically coupled with include:
  • Conveyor Belts
  • Pumps
  • Milling Machines
  • Stone Crushers
  • Mixers
  • Fans
  • Compressors

Who Uses Soft Starters?
Soft Starters see widespread use across many industries due to the wide array of applications that make use of them. Some industries that use Soft Starters include:
  • Food & Beverage
  • Textile
  • Lumber
  • Cement
  • Mining
  • Pulp & Paper Mills
  • Sanitation

Do You Know Your Full Load Amps?
The Full Load Amps (FLA) rating of the AC Drive must meet or exceed the FLA of the motor. To properly determine your AC Drive needs, you must size the drive based on Amps:
  • Identify the Full Load Amps (FLA)* of the motor
  • Select the AC Drive that meets or exceeds this FLA rating

Full Load Amps (FLA) refers to the current of the motor at its rated load and voltage. It is equal to the amps the motor draws while producing the rated output horsepower. For more information on determining your FLA, view the applicable section of this Knowledge Base entry.

Starts Per Hour
Another important factor when choosing your Soft Starter is the amount of starts per hour that you expect out of your application.

SSW06 & SSW07: Up to 10 starts per hour (with optional Vent Kit installed) at 300% Duty Cycle for 30 seconds.

WEG is one of the largest industrial electric control manufacturers, producing more than 21 million units annually and always striving to improve. Attention to detail is the hallmark characteristic at WEG. All products, including their line of AC Drives, are driven by the desire to increase efficiency. WEG manufactures reliable AC Drives with varying module attachments. Depending on the project environment and application, WEG provides a wide variety of product types, sizes, and technology.

WEG Products Include:
  • Variable Frequency Drives
  • AC Motors
  • Pushbuttons
  • Soft Starters

More about WEG

5 to 400 HP
230, 460, or 575V Models

from $603

25 to 1500HP
230, 460, 575V Models

from $1,444

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UL Type 1, 3R, 4, and 12
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