Soft starters for electric motors

Production of soft starters for electric motors according to the customer’s specifications for industrial and manufacturing enterprises. We manufacture systems and devices for soft starters of the engine, which significantly reduce the risks of breakdowns and repairs, increase the service life and efficiency of the equipment, and reduce the overall operating costs.

Our principles for solving the assigned tasks

  • Flexibility and speed in decisions
  • Energy efficiency
  • Environmental Safety
Soft starters Kiev, Ukraine

Soft starters Kiev, Ukraine

Modern and reliable power supply and automation solutions

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Soft starters

The performance of industrial equipment depends on the efficiency of the induction motors that drive automated lines and systems. In production, electrical machines with a squirrel-cage rotor are usually used, which have many advantages – high power, affordable cost, ease of maintenance and repair.

The only major drawback of induction motors is a rapid increase in torque and a short-term increase in current during acceleration, and the starting current can exceed the nominal value by 5-10 times. To protect the engine from wear and prevent voltage surges in the network, soft starters are used, which slow down the rotation of the rotor during start-up.

What is Soft starters?

The standard soft starter is a transformerless voltage converter designed to reduce inrush current and voltage. The soft starter is installed in front of the motor and reduces the output voltage, which the electric machine uses as input; during the set interval, the starting currents increase from zero to the set value, as a result of which the motor starts more smoothly.

Assign a soft starter

The main task of the soft starter is to match the rotor starting torque with the network load during the acceleration and stopping of the asynchronous motor. Usually, a soft starter is used when a powerful electric machine is connected to a low-power network; also the soft starter is used when starting the motor under voltage.

In addition to their immediate tasks, soft starters streamline the operation of control systems and stabilize the network, prevent overloads and underloads, short circuits, breakdowns and phase breaks, and in emergency situations ensure the rotor is locked. When installed in specific power circuits, the soft starter of the electric motor saves energy.

The principle of operation of the floating device

The soft starter circuit is built on bypass contactors and thyristors – semiconductor elements with one-way current flow, connected in anti-parallel. When current is applied to the control contacts, the thyristors change conductivity, reducing the starting voltage and the rotor speed.

The generator supplying signals to thyristors is controlled by a microprocessor, which provides communication with other devices, processing sensor signals and emergency protection. A smooth start of an electric machine through a soft starter is carried out in three stages, at the moment of start, a voltage is set, which is 30-60% of the nominal:

  1. The transmission gears alternately mesh with each other, tensioning the drive belts.
  2. The control processor gradually increases the conductivity of the thyristors and increases the rotor speed.
  3. When the rated speed is reached, the contacts of the contractors are closed, and the current rushes along the bypass paths, bypassing the thyristors. When the engine stops, the semiconductors are turned on again, and signals are received from the generator that reduce the conductivity of the thyristors until the electric machine is completely turned off.

Applications for soft starters

The use of a soft starter reduces the cost of starting circuits for electric motors, allowing you to abandon expensive items of equipment and expand the scope of asynchronous machines. Optimization of network parameters and extension of the service life of electrical equipment due to the installation of a soft starter is used in various fields of activity:

  • plant power equipment and automation systems;
  • household and industrial ventilation, heating and air conditioning systems;
  • oil rigs and refineries;
  • infrastructure, transport and utilities;
  • small and medium-sized construction (forklifts, compressors, VC systems);
  • infrastructure, transport and utilities;
  • agriculture and food industry.

Soft starters are installed in electromechanical, electronic and electrical devices, where there is a small acceleration moment affecting the operation of the motor and sensitive equipment. In some countries, when operating electric machines with a power of 15 kW or more, the installation of a soft starter is made a legal obligation.

Soft starters are compatible with light, heavy and extra heavy starting drive systems; it is most advisable to use the soft starter in easy start systems with infrequent engine starts. If the starts are made more than 20 times per hour, it is recommended to install a frequency converter that can reduce the starting currents by more than 200% of the rated value.

To prevent water hammer in industrial water supply systems, a pump soft start device is used, which matches the performance of pumping units with the liquid flow rate. Soft starters are also used in domestic pumping stations, where powerful borehole pumps are used to lift water from deep wells.

Types of soft starters

Voltage regulation in soft starters is performed in different ways, depending on the type of electric drive that serves the soft starter, select one-, two- or three-phase devices. A simple single-phase softstarter regulates the starting current and torque in light-start drive systems up to 11 kW and does not provide feedback. A reversing softstarter of the appropriate type is required for the regulation of two- and three-phase systems of medium and extra heavy loads:

  • two-phase soft starters – designed for electric drives up to 250 kW; application is possible in the absence of strict current limits;
  • three-phase soft starters – used in drive systems with especially severe starting conditions, with frequent switching on and off; the drive power is only limited by the properties of the semiconductors. The soft starter reduces the starting current to 300% of the nominal value in all three phases and smooths out the manifestations of phase asymmetry;
  • a synchronous soft starter can be used in combination with standard soft starters to share electrical appliances with different drive mechanisms.

Benefits of Soft starters

Compared to frequency converters and phase rotors, the soft starter provides the maximum reduction in starting current. The main arguments in favor of Soft starters are efficiency, compactness, simplicity and versatility; Installation of soft starters in industrial plants provides a number of technical advantages:

  • reduction of thermal stress, mitigation of dynamic shocks and jerks of mechanical equipment;
  • the ability to integrate into automation systems;
  • starting noise smoothing;
  • savings on hardware – the soft starter allows the use of less powerful switches and protection schemes;
  • prevention of accidents, injuries and damage to products due to jerks of the conveyor at startup;
  • extending the service life of industrial and power equipment;
  • reduced energy consumption.

Select soft starter

Soft starters for industrial systems are selected on the basis of calculation algorithms that take into account the characteristics of electrical equipment, operating conditions and key parameters of power grids – rated current and required reduction rate, duration of stops, level of heat production, number of starts per hour, etc. If you need to install an Soft starters, send the task for the calculation to the company “AVR Plus”, and we will offer the best solution, taking into account the characteristics of the network and the planned budget.

Certificates and Licenses

Schneider Electric Shield Panel Official Partner Certificate
Сертификат официального партнера щитовика Shneider Electric
List of types of construction works
Перечень видов работ по строительству объектов
License of the State Architectural and Construction Inspection of Ukraine
Лизензия государственной архитектурно-строительной инспекции Украины
Work permit
Разрешение на работы

Own production

Our own high-tech production, cooperation with manufacturers of reliable and modern components, as well as extensive experience in projects of various levels of complexity allows us to implement the ideas of our clients at reasonable prices.

We use only reliable components

We use only reliable components from well-known world manufacturers

Prices for electrical services


Prices for electrical services depend on the scope of the project, conditions and features of the installation of structures at the facility.


The price for electrical services is much lower if you order design, production and installation from our company.


The exact cost of electrical services is announced when calculating the estimate of the task.

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