Features and advantages of using electronic soft starters for a motor starting

Features and advantages of using electronic soft starters for a motor starting
Most machines have a motor system that is necessary to get them running. Now there are different methods to start an electric motor system with the help of a transformer, resistors, direct online motor. But an alternative and safer method for starting an electric motor is using a Soft Starter. In this article, we will help you understand the usage and advantages of electronic soft starters for motor starting. 

What is a Soft Starter? 

A soft starter is a device that can be added to an electric motor for a different start method. The main reason behind using a soft starter is to reduce the strain on a motor when the power is turned on. A soft starter helps in the gradual starting of a motor by applying increasing voltages. So there is no sudden start or burst of power but a smooth acceleration. It prevents possible damage to a motor and subsequently the entire machine. A soft starter gives a steady and linear slope of power. There are different types of soft starters available which can let you adjust the starting voltage and amount of time to fully power up an electronic motor. 

Here are some of the features of an electronic soft starter: 

  • Range setting adjustments of a working machine
  • Variable characteristics of current, voltage and torque
  • Bypasses power semiconductors after the motor starting to reduce loss
  • Limited number of starts per hour depending on the starting conditions and specifications 
  • Integrated into communication network 
  • Integrated motor protection against overcurrent, undercurrent or failure 
  • Designed to accelerate or decelerate electric motors 

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Why use a soft starter on a motor? 

Electric motors in commercial or industrial systems require a lot of electricity when they are accelerated. Using a soft starter reduces the torque and power load. It smoothens the operation process and avoids complications or sudden jolts in the machine. Here are some other advantages of using electronic soft starters: 

  • A soft starter helps to limit the transient voltages and protects against sudden power surges when the machine is in operation or there is a power outage. 
  • It helps in the smoother operation of the machine and reduces the risk of personal harm to the worker. 
  • A soft starter is easy to operate and is suitable for most types of induction motors. You just have to get it hooked onto the device and it will work properly. 
  • Using a soft starter can help to increase the life of the motor. A motor that otherwise runs on heavy currents is risked of damage and defects. 
  • Soft starters also protect the motor from overheating as it limits the current supplied during the start. It is useful for applications that require the motor to start and stop multiple times. 
  • Soft starters are energy efficient as they automatically reduce the load when the motor reaches full speed.
  • Compared to other alternatives like a VFD, soft starters are much cheaper. 

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How does a soft start motor starter work? 

To understand the working principle of an electronic soft starter, we will need to know its components. A soft starter essentially has two major components: 

Power circuit: This consists of Triac, which is a series of back-to-back thyristors that regulate the voltage supplied to the motor. Through this circuit, the current is circulated to the motor. 

Control circuit: This circuit controls, monitors and protects the components of a power supply circuit. 

When a pulse is applied to a set of thyristors, it allows the flow of current to energize the motor. The angle of each pulse determines how much current can pass and for how long. Thyristors can control the variation of firing angles which generates a voltage at the output. This voltage is gradually increased until it reaches the nominal point required. The duration of the current flow can be controlled by the user by setting the parameters of a current flow. The current is slowly applied to the motor, which allows the soft starter to reduce torque and power load. The soft starter controls the amount of voltage running through the motor’s circuits and allows for a smooth progression of the current. 

Soft starters are thus essential for a smooth motor start and maintenance of the long life of machines. If you want to get your hands on good quality and reliable soft starters, check out the range of feature-rich soft starters by Schneider Electric. They have a wide variety of industrial as well as commercial applications. Their soft starter solutions are very easy to setup and are designed to meet your applications' performance requirements, ensuring the safety and security of equipment and personnel.

What Are Some Common Applications of Soft Starters for Motors?

Below are some of the most common applications of soft starters for motors.

  • Water Pump- Soft starters are usually used in water and other liquid pumps. This is because these pumps always face a risk of power surges. In such cases, a soft start increases the pressure gradually to reduce the risks.

  • Conveyor Belts- These systems move heavy loads. So, they need optimization using a soft starter.

Soft starters are also used in fans and motors using pulleys and belts.

What Is the Advantage of Using Electronic Soft Starters?

Electronic soft starters offer the following advantages.

  • The size of these starters is quite small. Their small size results in low operational costs.

  • Soft starters are of very low cost.

  • They are simple to operate and smooth to start. These starters reduce bumps and knocks.

  • Soft starters do not cause jolts in the system. They do so by limiting the starting current and avoiding current peaks. These starters also include soft stops and protections.

  • These starters significantly contribute to energy savings.

What Is the Difference Between a Soft Start and a VFD?

Soft Starter


It regulates the AC voltage using thyristors.

It converts AC to DC and vice-versa of the required value.

It is a semiconductor-based motor starter. It is used to start and stop an induction motor.

It is also a semiconductor-based motor starter used to start and stop the induction motor.

A soft starter is bypassed by a contactor at full speed.

It operates throughout the operation of the motor.

It can change only the voltage supply.

It can change the voltage as well as frequency.

It is smaller in size than a VFD

VFD is larger than a soft starter.

Frequently Asked Questions

Q1. What is the purpose of a soft starter?

Ans: A soft starter is used to limit torque and decrease the inrush currents to prevent equipment from heating.

Q2. How is a soft starter different from a normal starter?

Ans: Normal starters allow maximum voltage to inrush into the equipment during its starting. However, a soft starter prevents the motor against mishaps by preventing excessive voltage inrush.

Q3. What causes a soft starter to fail?

Ans: A soft starter can fail due to failure of the soft starter itself. It can also fail due to unstable power supply voltage, incorrect parameter settings and failure of overload protection function.

Q4. What are the disadvantages of a soft starter?

Ans: Soft starters are unable to control the speed.

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