What is the difference between permanent magnet frequency converter and ordinary frequency converter?

Permanent magnet motors, also known as permanent magnet synchronous motors, are mostly permanent magnet variable frequency motors that are excited by permanent magnets without excitation windings, resulting in no excitation losses.

Compared with ordinary motors (or ordinary three-phase asynchronous motors), permanent magnet variable frequency motors do not have electrical excitation and corresponding losses. The permanent magnet rotor does not generate heat, and the electrical load can be selected

Very high, therefore small in size and high in power density.

With the rapid development of new motor control theories and rare earth permanent magnet materials, the performance of permanent magnet motors has been further improved, with the following advantages:

1. Efficient and energy-saving

Since the excitation magnetic field is provided by permanent magnets, the permanent magnet rotor does not require excitation and can achieve an efficiency of over 90%. Compared with asynchronous motors, permanent magnet motors have a wide range of high-efficiency operating speeds and significant energy savings. Especially during low-speed operation, the advantage is more pronounced.

2. Low temperature rise

The absence of electrical excitation in the rotor means no loss of heat generation, therefore, permanent magnet motors generally have a low temperature rise. Good starting performance: Due to the fact that the rotor winding of the permanent magnet motor does not function properly during normal operation, the rotor winding can be designed to fully meet the requirements of high starting torque, such as increasing from 1.8 times to 2.5 times, or even larger.

3. High power factor

The impact on the operation of the power grid lies in the fact that asynchronous motors have to absorb a large amount of reactive current from the grid, resulting in a large amount of reactive current in the power transmission and transformation system, which in turn reduces the quality factor of the grid and increases the load on transmission and transformation equipment and power generation equipment. At the same time, reactive current in the power grid or transmission and transformation system consumes some electrical energy, resulting in low operational efficiency of the power grid. Coupled with the low efficiency of asynchronous motors and the situation of absorbing more electrical energy from the grid, the loss of electrical energy is exacerbated, and the load on the grid is further increased.

The unique advantages of permanent magnet motor rotors, such as no electrical excitation and high power factor, help improve the quality factor of the power grid or eliminate the need for compensators in the grid. Improving power factor can also increase the utilization rate of transformers.