Soft Starters

Soft Starters (sometimes referred to as Reduced Voltage Soft Starters- RVSS) are a motor starter and protection device that can bring a motor up to speed in a programmed acceleration time. They control the voltage output to the motor, and gradually increase it to ramp the speed up to 100% speed. When stopped they can be programmed to coast or ramp in a similar fashion to control voltage and ramp down to 0% speed. The protections that most soft starters offer are: Locked Rotor, Motor Overload/Overcurrent, Phase Sequence/Loss, and Smooth Ramp Up (eliminating mechanical stress on motors & connected equipment).


How do Soft Starters Work?

Soft starters work by controlling the voltage supplied to the motor, gradually ramping it up from a low level to the full operating voltage. This gradual increase in voltage allows the motor to start smoothly, reducing the stress on mechanical components and minimizing electrical stress. The soft starter also provides adjustable overload protection, reducing the risk of electrical damage and improving system reliability.

Benefits of Using Soft Starters

Reduced Stress on Motors

One of the primary benefits of using a soft starter is the reduction of stress on the motor. By gradually increasing the voltage, soft starters reduce the mechanical and electrical stress on the motor, extending its lifespan and reducing maintenance requirements.

Lower Inrush Currents

In addition to reducing stress on motors, soft starters also limit the inrush current, which is the surge of current that occurs at start-up. This surge can cause damage to the electrical system, as well as increase energy consumption. Soft starters are designed to limit the inrush current, providing additional protection for the electrical system.

Improved Power Factor

The gradual acceleration provided by soft starters also improves the power factor, which is the ratio of active power to apparent power in the electrical system. An improved power factor can lead to reduced energy consumption, lower energy costs, and improved system efficiency.

Choosing the Right Soft Starter

When choosing a soft starter, there are several factors to consider, including the type of motor, the size of the motor, the voltage and current requirements, and any specific application requirements.

Type of Motor

The type of motor is an important factor when choosing a soft starter. Different types of motors, such as induction motors and permanent magnet motors, have different start-up characteristics and may require different soft starter configurations.

Size of the Motor

The size of the motor is another important factor when choosing a soft starter. Larger motors require more current at start-up, and therefore may require a larger soft starter.

Voltage and Current Requirements

The voltage and current requirements of the motor are also important factors when choosing a soft starter. The soft starter must be capable of handling the voltage and current requirements of the motor, as well as any specific requirements for the application.

Application Requirements

Any specific requirements for the application must also be considered when choosing a soft starter. This may include requirements for over-current protection, under-voltage protection, or thermal protection.