Kolmiodeltakytkentöjen

Kolmiodeltakytkentöjen, often translated as delta-wye or delta-connected starting circuits, are a method used in electrical engineering to reduce the starting current of three-phase induction motors. This technique is particularly useful for larger motors that would otherwise draw excessive current when initially powered up, potentially causing voltage sags and damaging equipment. The circuit employs a special connection scheme that temporarily reconfigures the motor windings during startup.

During normal operation, the motor windings are connected in a delta configuration, which provides the required torque and power. However, at startup, a control system switches the windings to a wye (or star) configuration. In a wye connection, the voltage across each winding is reduced to approximately 58% of the line voltage, which in turn significantly reduces the starting current. This lower current is typically around one-third of the current drawn by a direct-on-line start.

Once the motor has reached a sufficient speed, usually around 75-80% of its rated speed, the control system reverts the windings back to the delta configuration. This transition allows the motor to operate at its full voltage and power output. The switching is typically managed by a timer or by monitoring the motor's speed. The primary advantage of using kolmiodeltakytkentöjen is the substantial reduction in inrush current, leading to smoother starts and reduced stress on the power supply and motor components.