Is a Soft Starter or VFD the Best Choice for Your Motor?

With industrial manufacturing transitioning from analog to digital technologies, it can be hard to determine the best way to power your motors. Should you opt for a soft starter or VFD (variable frequency drive)? This blog post will discuss the advantages and disadvantages of both and will help you determine which is the best choice for your motor. Let’s dive in and see which one wins in the end!

Quick Overview

No, a soft starter is not the same as a VFD. A soft starter is used to reduce electrical current at start up and shut down, whereas a VFD regulates an AC motor’s speed and torque by varying frequency and voltage.

What is a Soft Starter?

A soft starter is an electrical device that reduces stress and strain on motors when starting. It does this by controlling the voltage applied to the motor by gradually increasing or decreasing it over a few seconds instead of immediately switching the full voltage on at once. This allows for a much smoother startup than traditional, direct-on-line starters, which have been known to cause instability in motor shafts, excessive heat generation and even mechanical damage.

Soft starters have their advantages and disadvantages compared with variable frequency drives (VFDs). On the one hand, they are cheaper upfront and can be installed more quickly than VFDs so may be preferable in certain use cases. On the other hand, they do not provide motor speed control, so are less suitable for applications where variable speed operation is required. Additionally they tend to generate more heat during operation than a VFD would.

In conclusion, soft starters offer cost savings upfront and are a viable option for some applications due to their quick installation times. However, they may not be suitable for often-shifting speed applications due to their lack of speed control capabilities and higher levels of heat generation. The next section will explore the differences between soft starters and VFDs in more detail.

  • While both a soft starter and a VFD are used for energy efficiency, the main difference between them is that a soft starter is used to reduce mechanical stress on motors during start-up and shut down of the motor, whereas a VFD is an adjustable speed drive used to reduce energy consumption throughout the operation of the motor.
  • A soft starter works by ramping up the voltage applied to the motor so that it starts up slowly. This reduces strain on mechanical components connected to the motor as well as being more energy efficient.
  • A VFD works by varying the frequency of the power supplied to the motor, thereby changing its speed. This gives more control over the motor’s operation, resulting in more efficient use of electricity.

Soft Starter vs. VFD

When comparing Soft Starters and Variable Frequency Drives (VFDs), it is important to understand each technology’s strengths and weaknesses in order to choose the best solution for specific applications. Soft starters provide gentle, soft-start acceleration and can protect a motor from overloads, but when compared to a VFD, they provide limited control over speed adjustment, smoother and adjustable acceleration, single-phase power supply capability, and energy savings.

Soft starters are designed to reduce inrush current and gradually ramp up a motor’s operating speed by controlling voltage or current. This prevents sudden starting impacts on the motor which helps preserve mechanical components as well as increase efficiency, but the limitations of soft starters mean that precision speed adjustment is not possible. In contrast, VFDs offer improved power management capabilities with reduced voltage, current limiting, rapid stopping and precise speed control. Furthermore, VFDs can be used on both three-phase and single-phase motors for additional flexibility depending on application needs.

Even though VFDs offer superior protection to both the motor as well as other electrical components, they do come at a cost and in some cases may not be cost effective or even needed. Because of this, one should always consider the individual application’s needs before making any decision or else waste money needlessly.

Ultimately, determining which of these two methods is best suited for a particular application comes down to the preferences of the user balanced against their overall objectives. This can be an arduous process to undertake properly so it is essential to first understand the differences between soft starters and VFDs as well as have a clear understanding of the desired outcome for a given application.

Now that we have a better understanding of what each technology provides let’s move on to explore the differences in power and control that exist between soft starters and VFDs in greater detail.

Differences in Power and Control

When assessing the best choice for a motor, understanding the differences in power and control between a soft starter and Variable Frequency Drive (VFD) is critical. Soft starters provide greater starting torque by gradually ramping up current to the motor, reducing peak starting current up to 40%. In comparison, a VFD affords more precise control over speed and torque, offering versatility that a soft starter cannot match. While they both can provide speed control of any motor, VFDs are more suitable for precision controls.

From an efficiency standpoint, while both soft starters and VFDs offer good energy savings when used appropriately, VFDs are able to provide greater energy savings due to their ability to maintain constant power output over varying torque or speed requirements. By regulating not just speed of application but also the entire power supply unit, as well as keeping an optimal load on the system at all times, VFDs are commonly considered the most efficient option on the market.

Ultimately, when choosing between a soft starter and a VFD for your motor, it’s important to consider your needs in terms of power and control. Both have advantages and disadvantages that should be weighed carefully before deciding with one is the best choice for your specific application.

The next section will cover the pros and cons of each option in further detail, helping you make an informed decision about which solution is best for your motor.

Pros and Cons of Soft Starter vs. VFD

When it comes to finding the best choice for motor control, there are two popular options: soft starters and variable frequency drives (VFDs). To determine which one is best suited for your application, consider the pros and cons of each.

Soft Starters

The main advantage of using a soft starter over a VFD is a lower initial investment cost. Soft starters are usually less expensive than VFDs, making them an attractive option for those with limited budgets. They also provide better overvoltage protection since they don’t require complex programming and installation like a VFD does. The setup process is simple and straightforward, making it easy to get a system up and running quickly.

Soft starters can be fragile, however. The internal components are sensitive to electrical spikes which can cause them to fail prematurely or even catch fire if not monitored closely. Furthermore, the process of slowing down or speeding up the motor when using a soft starter can take longer in some cases. Once the full load has been reached, the current draw will increase rapidly resulting in higher voltage drops that can damage equipment or cause premature failure.

Variable Frequency Drives (VFDs)

The primary benefit of VFDs is the adjustable speed they provide. By altering the frequency of electricity going to the motor, you can adjust its speed in a much finer way compared to soft starters. Additionally, they offer better noise reduction and feature built-in short circuit protection that helps prevent accidental overloading and damage. On top of that, modern VFDs can offer protection against both under- and over-voltage conditions as well as phase imbalance issues, making them quite safe to use in hazardous environments where other power components may be at risk from danger or shock hazards.

The downside to using a VFD is the complexity of installation and programming involved – something best left to electricians with appropriate knowledge and experience. The purchase price of a VFD is also normally higher than that of a soft starter due to its more sophisticated components and featureset. That makes it difficult for small businesses or contractors who have tight budgets but still require advanced control capabilities from their motors.

Now that we have reviewed both options between soft starters and VFDs, let’s take a deeper dive into commonly used setups for each solution in the next section.

Most Important Points to Remember

Soft Starters are usually cheaper than Variable Frequency Drives (VFDs) but can be fragile and take longer to speed up/slow down the motor. VFDs offer adjustable speed, better noise reduction and built-in protection against under/over voltage and phase imbalance – but may be too costly for small businesses or contractors with tight budgets. Both options need to be installed and programmed correctly by an electrician with appropriate knowledge and experience.

Commonly Used Soft Starter and VFD Setups

When it comes to powering an electric motor, the decision to use either a soft starter or variable frequency drive (VFD) is an important one. The type of setup used can significantly affect the mechanical performance, life of the motor, and overall cost of operation. To determine which setup is best for a given application, it is important to consider their respective advantages and disadvantages.

Soft starters are commonly used with larger motors that may require high starting torque such as pumps or conveyors. When used with these types of motors, there tends to be less stress on the machine since the power is gradually increased over time as opposed to immediately ramping up as you might see with a VFD. This gradual increase in torque also helps protect other system components from damage caused by sudden peak power requirements. Furthermore, soft starters tend to be a more cost-effective solution compared to VFDs in many cases.

VFDs are better suited for smaller electric motors that require lower starting torques than their larger counterparts. The speed control capability of a VFD allows applications such as fans and blowers to operate effectively at various speeds depending on the load requirement. In addition, VFDs can reduce energy costs by allowing systems to run more efficiently at different operating speeds which can result in significant savings over time.

In conclusion, it’s important to consider both soft starters and VFDs when determining the optimal setup for operating an electric motor. While both setups come with their own unique benefits and drawbacks, making the right choice will ultimately depend on the unique needs of each individual application. With this said, it’s now time to look at how protective measures can be taken to ensure system safety when using either a soft starter or VFD setup.

Protective Systems When Used with Soft Starters and VFDs

When it comes to the use of protective systems with soft starters and VFDs, there can be a strong argument for both. Soft starters typically offer fewer built-in protective measures when compared to VFDs, but they tend to include a range of adjustable parameters that can help limit faults and damage to motors.

On the other hand, VFDs tend to have multiple layers of protection built in, including overvoltage, undervoltage and motor overload protection, as well as pulse-width modulation and noise suppression features. This can be beneficial for applications in which motor failure could have drastic downstream effects.

Ultimately, which option is best for a particular application depends on the specific requirements and associated risks. For instance, if it’s essential to have a fast response time in order to keep equipment from stalling or failing too quickly, then a VFD may be the best choice. If protecting against motor overloads is the highest priority, then a reliable soft starter design combined with adequate instruction may be most suitable.

The next section of this article will discuss the benefits of soft starters compared to VFDs. As demonstrated above, their unique advantages and disadvantages should be carefully weighed when determining the most effective solution for an industrial application.

The Benefits of Soft Starters Compared to VFDs

The debate of Soft Starters versus Variable Frequency Drives (VFDs) is an important one for businesses to consider. The wide range of benefits available through either technology makes it difficult to decide which of the two methods is better suited for a given motor or application. Soft starters offer greater flexibility and convenience in applications where large jumps in torque are difficult to manage while VFDs provide more precise control, especially when speeds beyond maximum motor RPM are needed.

Soft starters offer many advantages over VFDs. Reduced load spikes at startup result in reduced stress on motors and other vulnerable components, which can lengthen the lifespan of both the motor and the underlying machinery. In addition, soft starters reduce current surges that are detrimental to electrical systems, making them well-suited for large motors and long runs of wire. With soft starters, you can also adjust ramping times as needed allowing for custom start/stop profiles.

Similarly, VFDs provide their own unique set of benefits. Due to their precise control over voltage and frequency, VFDs are able to generate smooth operation even with sudden changes in speed or direction. This allows them to achieve higher levels of efficiency that are difficult for soft starter ran motors to match due to their limited flexibility at lower speeds. VFDs can also reduce wear and tear compared to more traditional starting methods, making them attractive options for businesses seeking to increase the longevity of their equipment.

Overall, there is no clear winner between a soft starter and a VFD in terms of power flow management as each has its unique pros and cons. Depending on the type and size of motor being used and the desired output frequency range will determine which technology is most suitable for your application.

Conclusively, whether businesses choose soft starters or VFDs they must first assess their specific needs before making a decision. Next up: In the conclusion we discuss whether a soft starter or VFD is ultimately the best choice for every motor application.


When determining the best solution for starting a motor, it is important to consider both the soft starter and variable frequency drive (VFD) options. A soft starter provides a gradual acceleration which reduces stress on the motor and reduces utility cost for larger motors that require frequent starts. They can also provide flexibility with various voltage levels and are relatively easy to install. However, they are limited in performance capabilities and cannot accommodate large or high-powered applications.

A VFD provides solid start capability as well as features such as speed control, torque control, horsepower regulation, automatic sequence control, and soft stopping. These drives also allow for greater accuracy in controlling motor speed, which makes them suitable for a variety of applications. The main drawback to VFDs is the complexity of their setup and design, which can be costly and time consuming.

Ultimately, each technology has its advantages and drawbacks depending on the specific application requirements. Before selecting either option, it is important to assess factors such as type of motor, voltage level, motor size, power requirements, desired performance characteristics, complexity of setup/design and budget constraints in order to determine which best meets the needs of the application.

Frequently Asked Questions and Their Answers

What are the advantages and disadvantages of using a soft starter compared to a VFD?

The main advantages of using a soft starter compared to a VFD are that it is often simpler and more cost-effective for lighter load applications. Soft starters also provide reliable starting torque, water-resistant connections, and enhanced start-stop control. Additionally, because of their simplicity, they require less installation and maintenance costs than a VFD.

However, there are some key disadvantages to consider when selecting a soft starter versus a VFD. It can be challenging to obtain optimal motor protection when operating with a soft starter as they do not react to motor overloads by reducing electrical current like VFD’s do. Due to their fixed speed settings, soft starters lack the flexibility offered by a VFD to adjust frequency on the fly. Lastly, the motor starts more slowly in comparison with a VFD.

In conclusion, both options have their respective advantages and disadvantages and ultimately deciding which one is right for your motor depends on its application and specific needs.

Are there any specific applications for which a soft starter would be better suited than a VFD?

Yes, there are several specific applications for which a soft starter would be better suited than a VFD.

Soft starters have the advantage of providing a more gentle start, making them well-suited for applications with large motors that can experience high inrush current when starting. Soft starters also offer improved motor protection as they help limit thermal overload conditions and accelerate the motor’s ramping to its desired speed in a controlled fashion. Additionally, in processes requiring quick changes to acceleration or deceleration speeds, such as those found in packaging systems, soft starters are ideal solutions due to their ability to provide that rapid feedback.

On the other hand, VFDs are best used in applications where fine-tuned control of speed and torque is required. This enables VFDs to be used in more precision-based applications, such as fan and water pumps with constantly varying load demands. VFDs also provide high efficiency through variable frequency control, meaning that energy consumption is kept to a minimum.

In conclusion, it is important to carefully evaluate the needs of your application and decide whether a soft starter or VFD would be the best choice for you motor.

What are the differences between a soft starter and a VFD?

The primary difference between a soft starter and a VFD (variable frequency drive) is their method of controlling motor speed. A soft starter works by gradually increasing the voltage applied to the motor, allowing for more gradual increases in motor speed. Conversely, VFDs control motor speed by adjusting the frequency of the AC power supplied to the motor, allowing for precise and precise control of motor speed.

Soft starters can provide improved ramping up and slowing down times, but due to the reduced voltage that they supply, they generally require an external capacitor to satisfy reactive power requirements. Soft starters also create increased harmonics which affect nearby electrical systems.

In contrast, a VFD can achieve precise control over motor speed without sacrificing the full load current or starting torque ratings of a normal motor. While this precision comes at a cost of having to accurately manage both voltage and frequency, it is often preferable for applications where accuracy or control is paramount. Additionally, because VFDs increase or decrease frequency while maintaining voltage levels as they control speed, they typically offer lower harmonic distortion than soft starters do.