July 20, 2023

There Are Several Wiring Methods for Aluminum Shell Gear Motors

There are two connection methods for motors, delta connection and star connection. The star connection method is that the ends of the three windings are connected, and the first ends are respectively connected to the three live wires of the three-phase power supply. The delta connection method is that the three windings are connected end to end, and three wires are drawn from the three vertices to connect to the three live wires of the three-phase power supply.

For low-voltage high-power motors (>3 kW), in order to reduce the starting current (4-7 times or even higher than the normal operating current), the star-delta starting method is generally used to start the motor to avoid damage to transformers or other equipment. For high-voltage motors, star connection is mostly used to avoid damage to motor lines and insulation caused by high voltage.

Aluminum Shell Gear Motor

1. In delta connection, each winding of the three-phase motor bears line voltage (380V), while in star connection, each motor bears phase voltage (220V), and the withstand voltage of 220 coil windings is low.

2. In the case of the same motor power, the winding current of the delta motor is smaller than that of the star motor, which can reduce heat and loss.

3. When the motor is connected in star form, the starting torque is only half of the delta connection, but the current is only about one-third of the delta start. The current during delta starting is 4-7 times the rated current, but the torque is large. It is more suitable for star connection of small torque motors, and more suitable for delta connection of high torque and high power motors.

The difference between the characteristics of the two connection methods:

1. Delta connection method: it helps to increase the power of the motor, but the disadvantage is that the starting current is large and the winding withstand voltage (380V) is large. Increased insulation class.

2. Star connection method: it helps to reduce the withstand voltage of the winding (220V) and reduce the insulation level. The starting current is reduced. The disadvantage is that the motor power is reduced. Therefore, most of the low-power motors below 4KW use star connection, and those larger than 4KW use delta connection.

The delta connection motor is started by star-delta conversion method when starting at light load to reduce the starting current. Light load is the condition, because the star connection torque will become smaller, and the purpose of reducing the starting current is to use the star connection method to reduce the starting current. The power of the delta connection is large, and the starting current is also large, and the power of the star connection is small, and the starting current is also small.

How to deal with the local burning of the winding of the aluminum shell motor due to the problem of the end cover or insulation?

Because the end of the winding of the aluminum shell motor is long or partially damaged and rubbed against the end cover or other accessories, the winding is partially burned.

Corresponding countermeasures: When updating the winding of the motor, the wire must be embedded according to the original data. When the motor is overhauled, any rigid objects are not allowed to touch the winding. When the motor rotor core is pulled, the rotor must be lifted to prevent the stator and rotor cores from rubbing against each other. When using an open flame, the winding must be isolated from the open flame and kept at a certain distance. Before the motor is reassembled, the integrity of the winding should be carefully checked and diagnosed.

Due to the long-term overload or overheating of the aluminum shell motor, the aging of the winding insulation is accelerated, and the carbonization of the weakest point of the insulation causes short-circuits between turns, short-circuits between phases, or short-circuits to ground, which partially burn the windings.

Corresponding countermeasures: ①Try to avoid motor overload operation. ②Ensure that the motor is clean and has good ventilation and heat dissipation. ③ Avoid frequent start-up of the motor, and perform a dynamic balance test on the motor rotor if necessary.

The winding insulation of aluminum shell motors is subject to mechanical vibration (such as high current impact at start-up, vibration of the driven equipment, unbalanced motor rotor, etc.), which causes unfavorable phenomena such as inter-turn loosening and insulation cracks in the windings.