Key Advantages of Soft Starters for Motor Control

Soft starters are becoming increasingly popular in the industrial and commercial sectors due to their numerous advantages over traditional hard starters. These devices are designed to smoothly ramp up the voltage and current supplied to electric motors, reducing the stress and strain on the motor and the rest of the system. In this article, we will explore the many advantages of using soft starters in industrial and commercial applications.

Advantages of Soft Starters

The followings are the benefits of soft starters:

1. Low starting current

Soft starters control the acceleration during startup. A typical low-voltage motor will require six to seven times its rated current during starting. The soft starter can typically reduce those requirements to two-and-a-half to four times the motor-rated current during motor startup.

The benefit of such a process is the improved lifespan of your system as the mechanical stress on the motor and shaft has been reduced, as well as the electrodynamic stresses on power cables and the electrical distribution network.

2. Soft stop function

It is also possible to stop the motor as soft starters can gradually decelerate the motor to a controlled and safe stop. Combining your electric motors with a soft starter not only reduces starting risk, breakage, and maintenance downtime but also increases your production efficiency and results in stopping.

3. Wide application areas

Soft starters can be used in almost all applications where there are motors. The most common applications where soft starters are needed: an axial fan, band saw, bow thruster, centrifugal fan, centrifugal pump, circular saw, compressor, conveyor belt, crusher, cutter, escalator, grinder, high-pressure pump, hydraulic pump, lift/elevator, mill.

4. Complex circuit and motor protection functions

Soft starters protect motors by using preset thermal curves, selectable for different protection classes, utilizing PTC probes, and conducting phase supervision. Besides, soft starters protect machines by utilizing underload protection, overcurrent protection, locked rotor protection, etc. These protection parameters can be adjusted from the control unit of the soft starter.

5. Reduction in the mechanical wear

In applications such as pumps and compressors, which can require many starts per hour to maintain critical process flows or pressures, these reduced starting currents result in significantly less motor heating and longer motor life. A softer or less rapid increase in motor torque at motor starting can also greatly extend the life of belt-driven and mechanically geared equipment. Soft acceleration and deceleration reduce wear on belts, gears, chains, clutches, shafts, and bearings.

6. Dips and spikes protection

Soft starter minimizes the voltage sags on the distribution system when starting. This results in less disturbance on the electrical network. It also protects against hazardous voltage spikes as less current is drawn from the line supply. This means that line voltage dips can be reliably avoided.

7. Time-saving

Time savings in using soft starters are achieved through a quick and easy setup procedure, user-friendly operational design, the longer life of system equipment, and improved safety. Besides, a soft starter requires almost no maintenance other than keeping the fan vents clear and clean.

8. No harmonics generation

There is some misconception that soft starters induce harmonics into the network. However, the bypass contactor will be in the picture during the continuous operation where the current passes through the contactor which is the least resistant path. Hence soft starters have no contribution towards the harmonics in the network.

9. Water hammering reduction

Pump control option with sophisticated pump algorithms on both starting and stopping that minimize the pressure surges that cause water hammer. The pump control option will maximize the life of the pump and piping systems while minimizing the downtime caused by system failure.

10. No need for extra cooling

Internal run bypass contactors and overload protection eliminate the need for additional devices, reducing enclosure sizes, minimizing installation and wiring time, and reducing overall assembly size and cost. The integrated bypass ensures very low heat dissipation, so neither the product nor your enclosure overheats. This helps avoid the need for cooling ventilation.

11. Cost and energy saving

Soft starters are still the most economical solution in fixed-speed applications. The reduced inrush current during starting can result in lower utility bills due to the reduction in peak current demand charges.

The power absorbed by the motor gets values multiples of nominal current (In) on the direct start-up thereby this causing waste of energy. The soft starter reduces this effect and the current does not present impactive values until the startup process completes.

12. Advanced communication

System operating parameters can be monitored enterprise-wide through a communications network. You can increase uptime by providing data for process management and preventive diagnostics. Soft starters offer a variety of communication options, including Modbus, Ethernet, ControlNet™, DeviceNet™, and PROFIBUS™.

13. Inside-delta connection option

3 phase-controlled soft starters can be connected to a motor’s delta. Since the current flow inside the delta is 58% of the line current, a much smaller soft starter can be used, further enhancing the cost advantages of soft starters over VFDs.

14. Less heat dissipation

In a soft starter with an integrated bypass, the current is carried across the contactor, therefore no active solid-state components are on to generate more heat.