Starting of three-phase asynchronous motor
Release Date:
2024-04-03
However, when a three-phase asynchronous motor starts directly, the current can reach 6-7 times the rated current, which has a significant impact on the power grid, especially for high-power motors.
1. Direct starting
However, when a three-phase asynchronous motor starts directly, the current can reach 6-7 times the rated current, which has a significant impact on the power grid, especially for high-power motors.
2. Frequency sensitive resistor starting
Frequency sensitive resistor starting refers to connecting a frequency sensitive resistor in series with the main circuit when the motor starts, in order to reduce the starting current. Frequency sensitive resistors can smoothly change the starting current, have less impact on the power grid, and are a relatively ideal starting method. However, high-power frequency sensitive resistors are generally in the form of inductors, so they will generate large electromagnetic eddy currents during use, which will reduce the power factor of the power grid.
3. Reduced voltage starting
Reduced voltage starting mainly includes autotransformer reduced voltage starting and star-delta reduced voltage starting.
Autotransformer reduced voltage starting refers to the autotransformer lowering the motor voltage and simultaneously reducing the starting current during start-up. Typically, it is reduced to 55%-75% of the rated voltage. The advantage is that the starting voltage can be easily changed by varying the number of taps on the autotransformer. The disadvantage is that an autotransformer is required, which incurs higher costs.
Star-delta reduced voltage starting is a method that reduces the starting current by changing the motor's wiring to alter the starting voltage. It is only applicable to motors normally wired in a delta connection. During start-up, relays are used to connect the motor in a star configuration, at which point the voltage per phase of the motor is reduced to approximately 1/√3 of the original, and the motor speed reaches about 80% of the rated speed. The control relays then change the motor wiring to delta, and the motor begins normal operation. The advantages are cost savings by not requiring an autotransformer, along with simple wiring and higher reliability. The disadvantages are that the proportion of the starting voltage cannot be changed, and it cannot be used with motors that are normally connected in star.
Recommended News
Analysis of Causes for AC Servo Motor Failure
Three-phase AC servo motors are widely used, but through long-term operation, various faults may occur. Timely identification of the fault cause and corresponding treatment are important tasks to prevent the fault from expanding and ensure the normal operation of the equipment.
The working principle of a servo motor is relatively simple, but its efficiency is relatively high. The servo circuit is built into the motor unit, which uses a flexible shaft usually equipped with gears.
Single-layer winding three-phase asynchronous motor
A single-layer winding is one where only one active side of a coil is embedded in each stator slot, so the total number of coils is only half of the total number of motor slots.
Starting of three-phase asynchronous motor
However, when a three-phase asynchronous motor starts directly, the current can reach 6-7 times the rated current, which has a significant impact on the power grid, especially for high-power motors.
Striped appearance on the outer surface of motor housing extruded profiles
Hollow aluminum alloy profiles are produced using the flat flow split combination die extrusion process. This process presents a relatively increased difficulty in profile production, as the metal goes through a diversion and welding joint process, therefore, hollow profiles have weld lines.
The motor casing is a main component of the electric submersible pump motor.
The motor casing is a main component of the electric submersible pump motor, and its machining accuracy directly affects the quality of the electric submersible pump. Due to the motor casing's thickness being greater than its radius during turning with clamping holes, it is prone to oval deformation. The deformation generally ranges from 0.03 to 0.10 millimeters, which cannot meet user requirements. If this problem is not resolved, it will lead to significant economic losses in producing qualified products.