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HomeNewsMAINTEX DC brushless inverter motor: energy saving and environmental protection, longer service life

MAINTEX DC brushless inverter motor: energy saving and environmental protection, longer service life

MAINTEX brushless DC motors are energy-saving and environmentally friendly, and have a longer life. Variable frequency motors are the general term for motors driven by frequency converters. With the rapid development of frequency conversion speed regulation technology, various high-voltage frequency converters continue to appear, playing a huge role in energy saving in power plants.

In fact, the motor planned for the frequency converter is called a variable frequency motor; the motor can achieve different speeds and torques under the drive of the frequency converter to meet the needs of load changes. The general frequency conversion motor is derived from the traditional squirrel cage motor; the traditional motor is generally changed from a self-cooling fan to an independent fan, and the corona resistance of the motor winding insulation is improved. In some occasions that do not require high motor output characteristics, such as low power, and when the operating frequency is near the additional frequency, it can be replaced by a general squirrel cage motor.

The principle of variable frequency motor speed regulation:
From the three-phase asynchronous motor speed formula: n=60f(1-s)/p, it can be seen that changing the power supply frequency f, the number of pole pairs p of the motor and the slip rate s can achieve the intention of changing the speed.
From the perspective of the essence of speed regulation, different speed regulation methods are nothing more than changing the synchronous speed of the communication motor or not changing the synchronous speed. The speed regulation methods that do not change the synchronous speed are widely used in production machinery, such as the rotor series resistance speed regulation of the wound motor, the chopper speed regulation, the cascade speed regulation, and the use of electromagnetic slip clutches, fluid couplings, oil film clutches, etc. Speed regulation. There are multi-speed motors that change the number of stator pole pairs to change the synchronous speed, and the variable-frequency speed control of the stator voltage and frequency can be used to adjust the speed of the motor without commutation.
From the perspective of energy consumption concept during speed regulation, there are two ways of high-efficiency speed regulation and low-efficiency speed regulation: high-efficiency speed regulation means that the slip rate is constant, so there is no slip loss, such as multi-speed motors and frequency conversion speed regulation. And the speed regulation method (such as cascade speed regulation, etc.) that can recover the slip loss. The speed control method with slip loss is inefficient speed control. For example, the rotor series resistance speed control method, the energy is lost in the rotor circuit; the electromagnetic clutch speed control method, the energy loss is in the clutch coil; the hydraulic coupling speed control method , The energy is lost in the oil of the fluid coupling. Generally speaking, the slip loss increases with the expansion of the speed control scale. If the speed control scale is not large, the energy loss is very small.

Features of variable frequency motor:
Electromagnetic planning
For variable frequency motors, because the critical slip is inversely proportional to the power frequency, it can be started directly when the critical slip is close to 1. Therefore, overload capacity and starting function no longer need to be considered too much, but the key issue to be solved is how to improve The ability of the motor to adapt to non-sine wave power supplies and to ensure the service life of the motor. The method is generally as follows:
1) The main magnetic circuit of the variable frequency motor is generally planned to be under full condition. One is to consider that higher harmonics will make the magnetic circuit full, and the other is to appropriately increase the output voltage of the inverter in order to increase the output torque at low frequencies.
2) In order to suppress the higher harmonics in the current, the inductance of the motor needs to be appropriately added. However, the rotor slot leakage reactance is large, the skin effect is also large, and the copper loss of higher harmonics is also increased. Therefore, the size of the motor leakage reactance must take into account the rationality of impedance matching in the entire speed regulation scale.
3) Reduce the stator and rotor resistance as much as possible. Reducing the stator resistance can reduce the fundamental copper loss to compensate for the copper loss caused by higher harmonics.

Structural planning
In structural planning, the first thing to consider is the influence of non-sinusoidal power supply characteristics on the insulation structure, oscillation, noise, and cooling methods of the variable frequency motor. Generally, pay attention to the following issues:
1) For constant power variable frequency motors, when the speed exceeds 3000/min, special high-temperature-resistant grease should be selected to compensate for the temperature rise of the bearing.
2) To avoid shaft current, use bearing insulation for motors with a capacity exceeding 160KW. The main reason is that the asymmetry of the magnetic circuit is prone to occur, and the shaft current will also occur. When the currents generated by other high-frequency weights work together, the shaft current will be greatly increased, which will cause the bearing to be damaged by galvanic corrosion. Therefore, special insulation measures are generally adopted. .
3) Cooling method: generally use forced ventilation cooling, that is, the main motor cooling fan is driven by an independent motor.
4) For the vibration and noise of the motor, it is necessary to fully consider the rigidity of the motor components and the whole, and try to increase its natural frequency to avoid resonance with each force wave.
5) Insulation grade, generally F grade or higher, strengthen the insulation to ground and the insulation strength between turns, and especially consider the ability of insulation to withstand corona impact.