Soft Starter Technical Specifications – Everything You Need to Know

If you’re an electrical engineer in need of an overview of the technical specifications of soft starters, then look no further. We’ve got everything you need to know here in one handy guide. Whether you’re looking for information on voltage requirements, soft start type, or how to choose the right soft starter for your application, this post will answer all of your questions and make you a soft start expert in no time. Let’s get started and dive into the specs!

Quick Summary of Key Points

Soft starters typically require voltage and frequency ratings, inrush current ratings, override time settings and stall torque values. For specific technical details, consult your soft starter manufacturer’s documentation.

Overview of Soft Starters

In industrial and manufacturing settings, a soft starter is an ideal way to start a motor’s rotation. It’s designed to reduce the mechanical stress placed on motors, which can prevent damage from occurring. To ensure your facility has one of these soft starters installed, understanding their technical specifications is important for optimal performance and efficiency.

Soft starters control when a motor starts and stops running with main characteristics like voltage and current. In other words, they determine how quickly a motor starts up or shuts down. This reduces excessive in rush currents at start-up which can affect both the electrical power system and the motor itself. Soft starters have been found to also improve efficiency and increase productivity.

This overview highlights the obvious benefits of soft starters but it’s important to recognize the drawbacks as well. Installations can become quite costly, especially if you require multiple installations of soft starters due to the number of motors you need working in the factory. And even though soft starters present better control over acceleration and deceleration of the motor, achieving precise speed control is not always possible due to its less-than-accurate starting mechanism which may incur some losses in production output.

So now that we’ve gone over the general overview of soft starters, let’s examine what makes them work individually. We’ll look at how they control electrical motors by using electronic circuits to manipulate voltage and current levels, increasing the effectiveness of their operations while simultaneously decreasing damage done to vital components.

How Do Soft Starters Work?

Now that a general overview of soft starters has been established, it is important to discuss how they work. To do so, it helps to first define a few terms. A soft starter is an electronic device that manages the torque produced by the electrical motor during start-up. This helps manage the amount of current used when powering up. The parameters set in the soft starter determine the characteristics of the system’s start-up process, such as its acceleration rate and whether any overcurrent protection is active.

As far as operation goes, when a three phase induction motor is powered on, its rotor will pass through a phase shift to catch up with the Stator. If this process happens too quickly, it can cause torque fluctuations and large voltage fluctuations from the power supply. A soft starter works by reducing those excessive torques and voltages so that it does not reach dangerous levels for the motor or electricity grid. This can be accomplished by controlling the amount of current provided to the motor so that no single peak current is too high and by setting ramp times which slow down the starting process over time.

The effectiveness of using a soft starter compared to other methods like reduced voltage start-ups and auto-transformer start-ups is often debated, with supporters of each approach arguing strongly either in favor or against one another. On one side of the argument there are those who point out that while Soft Starters are more expensive at first, they are more efficient, offer more control than reduction start-ups and can often reduce energy costs significantly in applications where a lot of start-up cycles occur daily. However opponents point out that soft starters produce harmonics that can be detrimental for certain types of installations as well as requiring additional control components like bypass contactors which also add cost. Ultimately it depends on your specific application and what you prioritize most; cost savings or maximizing power quality?

Now having discussed technical specifications and how soft starters work, let us move on to some of their typical applications for which they can provide great value for businesses looking to get the most from their current electricity solutions

  • Soft starters can reduce motor inrush current by as much as 80%.
  • Soft starters provide an automatic reduction of current when starting to protect against circuit overloads.
  • A study published in 2017 found that the addition of a soft starter to motors can extend the motor’s lifespan, reduce downtime and enhance equipment safety.

Typical Applications For Soft Starters

Once the basics of how Soft Starters work have been understood, it is important to understand what typical applications they are used for. Soft starters are commonly used in agriculture, manufacturing, and other industrial applications. They are most commonly used for pumps and large motors because their soft start capabilities make them ideal for starting and stopping these powerful machines without damaging the motor or causing large voltage spikes on the power supply. The ability to control the current draw is also useful in setting limits on specific types of machinery that require a consistent amount of power.

Moreover, when used with compressors or fans, Soft Starters allow users to reduce the starting torque needed by gradually increasing the output over time until it reaches its operating speed. This reduces both stress and wear-and-tear on motors while ensuring that it runs at the optimum level of efficiency. By providing consistent voltage over time, Soft Starters also reduce harmonic distortion which can damage equipment or interfere with other medical devices that use similar frequencies.

Soft Starters are becoming increasingly popular as autonomous technology advances because their safe start/stop capabilities make them ideal for automated controls. They give users the ability to consistently monitor and adjust machine operations from a central command system leading to greater efficiency from production machines. All in all, these versatile pieces of technology are invaluable in automotive service centers, shipyards, mining operations, and countless other industries that require consistent yet gentle starts for their power equipment.

This overview provides an understanding of why Soft Starters are invaluable pieces of technology but now more must be learned about the features which make them so successful and reliable. As technology advances, Soft Starter Design has become more sophisticated featuring new features such as variable frequency drives (VFD). In the next section we will discuss such features in detail and explore how they provide even greater levels of control over applications compared to earlier models.

Features of Soft Starter Technology

Soft starter technologies have a number of advantageous features which make them widespread in the industry. First, soft starters can provide a smooth torque during acceleration by limiting the voltage applied to the motor terminals allowing it to start without any sudden jerks in torque. This makes it ideal for reducing wear and tear on both motors and mechanical drive systems. Secondly, these starters are more adjustable than traditional starters as they allow more specific control on ramp up timing, acceleration rates and current limits. This makes them invaluable in managing highly sensitive machines and processes where short-term overload of equipment can cause serious damage.

Lastly, soft starters also boast sophisticated motor protection features that help protect both components and operators from potentially hazardous conditions such as locked rotor current and thermal overloads. Many modern starters can even detect ground-faults and automatically shut down the system when required. By being able to monitor many different conditions simultaneously, these starters offer an extraordinary level of efficiency and safety for industrial operations.

In conclusion, soft starter technologies offer a wide range of innovative features that make them incredibly reliable solutions for controlling many different kinds of industrial applications. Despite the undeniable advantages these starters present, their suitability for each specific application must be carefully considered to maximize their effectiveness. Therefore, we will now take a look at the advantages and disadvantages of using soft starters in industrial systems to gain a better understanding of when these devices should be used most effectively.

Advantages and Disadvantages of Soft Starters

Soft starter technology has its advantages and drawbacks, as do any other motor control methods. Some of the main benefits to using soft starters include their ability to reduce motor wear and increase motor efficiency, as well as their cost effectiveness compared to other motor control options. Furthermore, the ability to adjust run-times for specific processes or applications helps users save energy, resulting in further cost reductions.

One of the major drawbacks of using soft starters is that they can cause harmonics or voltage spikes on the line where it’s located due to their use of chopping techniques. This can lead to interference with other equipment in close proximity, as well as affecting load performance. Additionally, if not set up correctly, they may not provide sufficient ramp rates during starting cycles, causing excessive current draw and thus leading to more mechanical stress on the motor and increased wear.

It is important that those looking into installing a soft starter consider all the possible ramifications of its use. Through proper configuration and setting the correct parameters, many of these potential issues can be avoided while still enjoying the many benefits this technology offers. With proper maintenance and regular monitoring, organizations can take full advantage of soft starter technology while also ensuring that it’s installed safely and securely. All of these factors will come together to create an efficient operating system that meets industry safety and reliability standards.

Now that we understand the advantages and disadvantages that come with using soft starters, let’s look closer at another important factor: their operating temperature range and how this affects their performance.

Operating Temperature Range for Soft Starters

When considering the operating temperature range of soft starters, it is important to be aware of their limitations. While these devices can help increase machine performance and protect equipment from potential damage, they may not function as expected in extreme temperatures.


Soft starters are generally considered to be more reliable than traditional direct-on-line (DOL) starting methods due to the fact that they have a much lower chance of motor circuit failure at high temperatures. This is because the current flow through the motor is kept at manageable levels when operating via soft start. Additionally, this method of starting reduces current peaks which ultimately help to reduce losses associated with inefficient operation of the motor. Furthermore, utilizing soft starters can help prevent medical trips by allowing for smoother startup procedures, thus minimizing shock and providing greater protection for sensitive machinery that would otherwise be exposed to damaging thermal cycling effects during DOL start up.


However, some manufacturers may specify that their soft starters must not be used in extremely hot or cold conditions because it may lead to performance deterioration or even catastrophic failure due to overheating or expansion/contracting caused by extreme temperature changes. For example, if the maximum ambient temperature exceeds 140 degrees Fahrenheit (F), many soft starters will trip to avoid overheating. In addition, below freezing temperatures may cause the device to fail if its components become brittle and crack due to brittleness. Therefore, utilization of a suitable enclosure with proper ventilation should always be taken into consideration when selecting an enclosure for installation.

The need for careful consideration when selecting an enclosure in regards to temperature range is also important when performing an environmental audit as pertains to ROHS compliance and other applicable standards that manufacturers must adhere to regarding environmental concerns. These considerations will ensure that any air-cooled soft starter works optimally in its designated environment. Ultimately, this could save organizations money on needed repairs and replacements due to prolonged improper operation in extreme temperatures, as well as mitigate any risk associated with faulty components from time temperature exposure.

Common Questions and Their Answers

What different models of soft starters are available?

There are a variety of different models of soft starters available, each offering their own set of features and applications. The most common type is the non-regenerative soft starter which uses Thyristor technology to reduce motor starting current and voltage. This type of starter is generally used for motors that do not require high torque or fast ramp rates.

Another type of soft starter is the regenerative soft starter. It works by actively returning some of the extra kinetic energy produced by the motor back into the power supply, meaning it can handle higher torque loads as well as faster starting times than a non-regenerative soft starter.

Finally, there is also the harmonic driven frequency inverter soft starter, which uses a variable frequency approach to adjust its speed and acceleration profiles. This type of soft starter offers greater control over motor performance but requires additional dynamic components such as filters and cooling systems to operate efficiently.

In summary, there are three main types of soft starters available: non-regenerative starters, regenerative starters, and harmonic driven frequency inverter soft starters. Each type offers its own advantages and disadvantages for various applications so it is important to research which one best suits your needs before making a purchase.

What kind of controls and protection do soft starters offer?

Soft starters offer a wide range of controls and protections in order to ensure smooth and safe operation, as well as increase the life of electrical motors.

One of the most important features offered by soft starters is adjustable motor starting current– that is, the ability to set a maximum current limit when starting up the motor, so the user has more control over how much power is used. This can prevent large voltage drops, circuit overloads, and noise or vibration associated with sudden impact loads.

Soft starters also provide thermal protection for motors. By monitoring heat levels, soft starters are able to shut off motors if they become too heated in order to protect them from damage. Additionally, they can reduce damage from incorrect wiring or single-phase operations.

Finally, soft starters may offer CT/VT input for monitoring power which allows users to track data related to voltage, current, frequency and power used during start up– giving them the necessary information needed to make informed decisions about their operations.

What are the power requirements for different types of soft starters?

The power requirements for different types of soft starters depend on the size and application of the motor being controlled. Generally speaking, the minimum starting power requirement for a soft starter is proportional to the motor’s rated current.

For a standard three-phase motor, this can range anywhere from as little as 5 amps to as high as 2000 amps. The higher power ratings are typically reserved for industrial applications such as water pumping or large machinery. A common example is a 400 amp motor starter, which would require at least 1600 amps of incoming power to accommodate the startup demand.

The amount of starting power required may also differ depending on the type of soft starter in use. For instance, an AC line reactor will require more starting power than an electronic or voltage control option. Additionally, larger motors may require additional control devices (such as contactors) which can further increase the necessary starting power.

It’s important to note that the total system load must always be taken into account when calculating the desired power requirements. This is important because it may exceed the initial starting requirements and potentially cause problems with overload protection settings or overload tripping. For instance, a 1200 amp soft starter designed to handle a 400 amp full load could still potentially trip its overload protection if additional equipment was running at the same time on the same circuit.

To ensure proper operation, it’s essential to select a soft starter that meets both your motor’s rated current and your overall system load requirements. In addition to verifying the stated ratings, it’s also important to consult with technical experts who can advise on any additional measures that may need to be taken in order to ensure safe, effective operation.