A soft starter is a device responsible for gently starting an electric motor. It works by gradually increasing the voltage, which limits the starting current and torque. As a result, the motor starts smoothly, without any sudden impact on mechanical components, and the power supply network is free from adverse current peaks. Although soft starters and inverters may seem similar at first glance, their applications differ significantly.
Traditional direct-on-line starting causes the motor's rated current to be exceeded several times over. This, in turn, translates into significant stress on the couplings, bearings, and gears, shortening the life of the entire drive. A soft starter eliminates this problem by gently bringing the motor up to speed and reducing the load on the system. As a result, the machine starts stably, and other devices connected to the same network are not affected by voltage drops.
Where does a softstarter make the most sense?
Soft starters are best suited for applications where starting torque control and mechanical protection are essential. This is particularly true for pump, fan, conveyor, compressor, and mixer drives. In such systems, soft starters prevent sudden overloads and vibrations that could damage the installation. In pump systems, soft starters also protect pipelines against water hammer, a sudden increase in pressure during motor shutdown.
It's also worth using in locations where the motor starts frequently. Cyclic starts and stops are particularly taxing on a traditional DOL (Direct On Line) system, while a soft starter allows for current reduction and gentle acceleration of the drive. This allows for reduced component wear and significantly lower operating costs.
Softstarter or inverter - what to choose?
The choice of device depends on the application's needs. A soft starter is used where smooth motor starting and safe stopping are required, while an inverter is useful where speed regulation is necessary during operation. In many simple systems, such as pumps, fans, or fixed-speed conveyors, a soft starter is a simpler, less expensive, and less prone to failure solution.
An inverter offers greater capabilities, but also involves higher purchase costs and a more complex configuration. A soft starter, on the other hand, is most effective when the drive always operates at a single speed and does not require dynamic torque control.
Advantages of using a soft starter
The greatest advantage of soft starting is protecting the drive from mechanical and electrical overloads. Limiting the starting current reduces wear on system components and improves the overall system's stability. In the case of the mains, limiting the starting current also means fewer voltage fluctuations and reduced electromagnetic interference.
Soft starters improve not only machine operation but also their durability. Furthermore, modern models are equipped with diagnostic functions, monitoring current, voltage, and temperature. In the event of an overload, they can automatically stop the motor, protecting it from damage. Increasingly, they can also be integrated with PLC or SCADA control systems, allowing maintenance departments to respond more quickly to potential problems.
When is a soft starter not enough?
A soft starter, however, isn't a universal solution. It doesn't regulate the motor's speed during operation, so it's not suitable for applications requiring variable speed or precise positioning. In such cases, an inverter remains the only reasonable option. A soft starter also requires the proper selection of voltage and current ramps. Too short a start-up time can prevent the motor from accelerating smoothly, while too long a start-up time can cause it to overheat.
A soft starter is used in conditions where smooth operation, mechanical protection, and ease of use are essential. It is used wherever the motor operates at a single speed and requires gentle starting without excessive loads. It is a cheaper, less complex alternative to an inverter, which can significantly extend the life of drives and mechanical components.
Modern manufacturing plants increasingly consider soft starters as standard drive protection. This compact device can effectively safeguard fundamental processes and reduce the risk of failures, which can be the most costly in industry.
