Soft Start Devices for Electric Motors
The start-up of electric motors is always accompanied by a significant surge in current and mechanical load. To reduce these negative effects, it is recommended to use a soft start device.
What is a soft start device?
A soft start device is a mechanism that controls the initial characteristics of the electric motor's start-up. It softens the processes of starting and stopping, helping to avoid excessive heating and jerking, as well as extending the operational life of the equipment. These devices are typically used in asynchronous electric motors.
Purpose of Soft Start
Soft start devices are used for:
- gentle acceleration of the motor;
- gentle stopping of the motor;
- reducing the starting current;
- matching the motor's torque with the load torque.
Advantages of Using Soft Start
During the start-up of an electric motor, starting currents can exceed nominal values by 6-8 times, leading to voltage drops in the electrical network. This can negatively affect other electricity consumers or even render the motor unable to start at all. A soft start device gradually ramps up the starting currents from zero to nominal values, controlling the voltage on the electric motor's windings. This helps to keep the motor's parameters within safe limits.
The correct selection of a soft start device can significantly increase the electric motor's longevity by:
- eliminating jerks in the mechanical part;
- reducing heating of the windings;
- eliminating hydraulic shocks in pipes and valves;
- increasing the safety of the electric motor's operation;
- saving electrical energy.
Moreover, it allows for the integration of an automated control system (ACS), which saves human and time resources.
Selecting a Soft Start Device
The decision to equip an electric motor with a soft start device is up to you. If you do not wish to spend extra money, you can install the device yourself, but its purchase is mandatory.
When selecting a soft start device, it is important to consider the requirements for the mechanism and the characteristics of the electric motor. All specifications are usually provided in the operating manual. Errors in selection can lead to unreliable operation of the device. It is also important to pay attention to the speed range to choose the optimal combination of the frequency converter and the electric motor.
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