Soft starters

Why soft starters?

The soft starters are electronic motor control devices that facilitate optimal starting and stopping three-phase induction motors. This comes under drive technology.

From people's daily life to industrial applications, motors are used widely for ease of work. It’s an expensive investment and a crucial part of the equipment/system. The failure of the motor may create financial and commercial losses.

How to minimize this risk?

Losses can be minimized in two ways.

1. When a motor starts directly, the starting current may go up to fifteen times as high as the rated operating current. In that case, the entire power supply system has to be designed for that. This can be avoided by using soft starters.
2. In direct-start, the starting torque and breakdown torque can be between two to four times the rated torque of the motor. The sudden higher torque applied to the load (For example- a Pump) by the motor may create mechanical damage to the entire system. The lifespan of the complete system can be improved by using soft starters.

The main component of the soft starters is the thyristors/SCRs (Silicon-controlled rectifier). During the start and stop of the motor, the thyristors/SCRs will limit the current. The ramp time can be programmed in some of the soft starters’ models. Besides the start and stop controls, a soft stater has no other controlling function over the motor.

Where to use soft starters?

Soft starters are recommended instead of direct switches for 3 phase induction motor operation, it controls the starts and stops of the motor. Thus, protects the motor/pump/equipment from the electrical and mechanical damages creates by the direct start. When comparing to a VFD (Variable Frequency Drive), soft starters are an economical solution for controlling the start and the stop of the motor.

Some application example for usage of soft starters are:

• Roller conveyor application
• Hydraulic pump application
• Dust collector fan system
• An agitator with heavy loads

For all the examples mentioned above, the main requirements are :

• Reduction of the motor’s starting current
• Adjustable voltage ramp to avoid mechanical damage due to torque
• Smooth start and stop of the system to protect the equipment

Soft starters in stock at Automation24: How to choose the right one?

Select the size of your soft starters according to the rated motor current. To that, make sure that the rated current of the soft starter is greater or equal to the rated motor current.

At Automation24, you can find a range of high-quality soft starters from Siemens in various sizes and with different operating performances up to 18.5 kW. The SIRIUS 3RW30 and 3RW40 series soft starters will cover all your standard and difficult applications. For normal starting (Class 10), depends on the application either 3RW30 or 3RW40 can be used. For Heavy duty starting (Class 20) applications 3RW40 is recommended.

In case soft starters aren’t the perfect device for your application, you can also find a big range of other motor starters and load feeders at Automation24. And if your application requires and VFD you can find a big selection of them under the category variable frequency drives.

Increase the lifespan of your equipment/system by using soft starters instead of the direct start. Buy soft starters of Siemens, the global leader in Electrical gear, at Automation24. All products are in stock and will be shipped immediately after your order.