Small motors can be started with a

Small motors can be started with a switch or circuit breaker connected to the power source. Large motors must be matched to a special switching unit, which can be referred to as a motor starter or motor contactor. 了; For example, as shown in Figure 3. When starting, a direct starter (DOL) connects the motor directly to the power source. A step-down starter, Y-Δ reversing starter, or soft starter also connect the power supply to the motor through a step-down circuit, and then the voltage gradually increases and increases gradually. Smaller motor starters may only be serviced by staff. Magnetic contactors are commonly used with larger motors or motors that require remote control or automatic control. Medium voltage power supplies (approx.A DOL motor starter (Direct On Line) supplies the entire line voltage to the motor terminal and is the easiest motor starter to use. Starters that start directly in the network can also contain better protection components. The low power online starter can be operated manually, the high power starter can alternatively use electromechanical contactors (relays) to switch the motor circuit, or solid state electronics can be used for direct online start of the starter.If a high inrush current of the motor is started, it will not cause an excessive voltage drop in the power supply, and at this point the online direct starter will be used. The maximum engine power that the starter can handle is also limited by the power source. For example, some rural electrical equipment may require motors greater than 10 kW and use decompression engine starters.Sometimes the online starter can be used to directly start smaller ones like water pumps, compressors, fans and conveyor belts. However, like a squirrel cage motor, if the motor is to be started directly online, there will be a high inrush current prior to acceleration at full speed, around 6 to 7 times the rated current at full load, which can lead to increased damage the work equipment. To reduce the starting current on large motors, slow starters or frequency converters are used to reduce the voltage drop in the power supply during the start-up process.The reversible motor starter can rotate the motor forward or backward. This type of starter includes two sets of circuits to directly start the online starter for forward and reverse rotation and has a mechanical or electrical interlock to prevent two circuits from operating at the same time. AC motors can swap two phases to achieve reverse rotation, and single-phase AC or DC motors may require other equipment to achieve reverse rotation as well.