Käivitusvoolu

Käivitusvoolu, also known as inrush current or starting current, is the maximum instantaneous current drawn by an electrical device, especially an electric motor, when it is first energized. This surge of current is significantly higher than the device's normal operating current. It occurs because at the moment of startup, the motor's windings have no magnetic field, and therefore, the inductive reactance is minimal. This low impedance allows a large current to flow from the power source.

The magnitude of käivitusvoolu depends on several factors, including the motor's design, its size, and the voltage applied. For many motors, the starting current can be anywhere from five to eight times the full-load running current, and in some cases, it can be even higher. This high current is temporary and typically lasts for a very short duration, usually a fraction of a second to a few seconds, until the motor reaches its normal operating speed and the magnetic field stabilizes.

Understanding käivitusvoolu is crucial in electrical engineering and system design. It affects the sizing of power supply components, such as circuit breakers, fuses, and wiring. If these components are not adequately rated to handle the starting current, they can trip or fail, leading to disruptions or damage. Soft starters and variable frequency drives are often employed to manage and reduce the inrush current, thereby protecting the motor and the electrical system from stress.