Frequency Conversion 100kw Permanent Magnet Motor PM OEM ODM

What applications use PMSM motors?

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Industries that use PMSM motors include Metallurgical, Ceramic, Rubber, Petroleum, Textiles, and many others. PMSM motors can be designed to operate at synchronous speed from a supply of constant voltage and frequency as well as Variable Speed Drive (VSD) applications. Due to high efficiency and power and torque densities, they are generally a superior choice in high torque applications such as mixers, grinders, pumps, fans, blowers, conveyors, and industrial applications where traditionally induction motors are found.

Advantages Of Rare-earth Permanent Magnet Motors

High efficiency: The efficiency curve of the asynchronous motor generally falls faster under 60% of the rated load, and the efficiency is very low at light load. The efficiency curve of the rare earth permanent magnet motor is high and flat, and it is in the high-efficiency area at 20%~120% of the rated load.

High power factor: The measured value of the power factor of the rare earth permanent magnet synchronous motor is close to the limit value of 1.0. The power factor curve is as high and flat as the efficiency curve. The power factor is high. Low-voltage reactive power compensation is not required and the power distribution system capacity is fully utilized.

Stator current is small: The rotor has no excitation current, the reactive power is reduced, and the stator current is significantly reduced. Compared with the asynchronous motor of the same capacity, the stator current value can be reduced by 30% to 50%. At the same time, because the stator current is greatly reduced, the motor temperature rise is reduced, and the bearing grease and bearing life are extended.

High out-of-step torque and pull-in torque: Rare earth permanent magnet synchronous motors have higher out-of-step torque and pull-in torque, which makes the motor have higher load capacity and can be smoothly pulled into synchronization.

Disadvantages Of Rare-earth Permanent Magnet Motors

High cost: Compared with the asynchronous motor of the same specification, the air gap between the stator and the rotor is smaller, and the processing accuracy of each component is high; the rotor structure is more complicated and the price of rare earth magnetic steel material is high; therefore, the motor manufacturing cost is high, which is common for asynchronous motors About 2 times.

Large impact at full power start: When starting at full pressure, the synchronous speed can be drawn in a very short time. The mechanical shock is large. The starting current is more than 10 times the rated current. The impact on the power supply system is large, requiring a large capacity of the power supply system.

Rare-earth magnet steel is easy to demagnetize: When the permanent magnet material is subjected to vibration, high temperature, and overload current, its magnetic permeability may decrease, or the demagnetization phenomenon occurs, which reduces the performance of the permanent magnet motor.

PM motor structures
PM motor structures can be separated into two categories: interior and surface. Each category has its subset of categories. A surface PM motor can have its magnets on or inset into the surface of the rotor, to increase the robustness of the design. An interior permanent magnet motor positioning and design can vary widely. The IPM motor’s magnets can be inset as a large block or staggered as they come closer to the core. Another method is to have them embedded in a spoke pattern.

PM motor inductance variation with load
Only so much flux can be linked to a piece of iron to generate torque. Eventually, the iron will saturate and no longer allow flux to link. The result is a reduction in the inductance of the path taken by a flux field. In a PM machine, the d-axis and q-axis inductance values will reduce with increases in the load current.

The d and q-axis inductances of an SPM motor are nearly identical. Because the magnet is outside of the rotor, the inductance of the q-axis will drop at the same rate as the d-axis inductance. However, the inductance of an IPM motor will reduce differently. Again, the d-axis inductance is naturally lower because the magnet is in the flux path and does not generate an inductive property. Therefore, there is less iron to saturate in the d-axis, which results in a significantly lower reduction in flux with respect to the q-axis.

Flux weakening/intensifying of PM motors
Flux in a permanent magnet motor is generated by the magnets. The flux field follows a certain path, which can be boosted or opposed. Boosting or intensifying the flux field will allow the motor to temporarily increase torque production. Opposing the flux field will negate the existing magnet field of the motor. The reduced magnet field will limit torque production, but reduce the back-emf voltage. The reduced back-emf voltage frees up the voltage to push the motor to operate at higher output speeds. Both types of operation require additional motor current. The direction of the motor current across the d-axis, provided by the motor controller, determines the desired effect.

Structure of the IPM (interior permanent magnet) motor

A conventional SPM (surface permanent magnet) motor has a structure in which a permanent magnet is attached to the rotor surface. It only uses magnetic torque from a magnet. On the other hand, the IPM motor uses reluctance through magnetic resistance in addition to magnetic torque by embedding a permanent magnet in the rotor itself.

SPM.IPM Motor Rotor Structure

IPM (Interior Permanent Magnet) Motor Features

High torque and high efficiency
High torque and high output are achieved by using reluctance torque in addition to magnetic torque.

Energy-saving operation
It consumes up to 30% less power compared to conventional SPM motors.

High-speed rotation
It can respond to high-speed motor rotation by controlling the two types of torque using vector control.

Safety
Since the permanent magnet is embedded, mechanical safety is improved as, unlike in an SPM, the magnet will not detach due to centrifugal force.

Vector Control Features

While a conventional system (120-degree conduction system) has the current impressed in the motor as a square wave, a vector control impresses voltage which turns into a sine wave towards the rotor's position (angle of the magnet), so it becomes possible to control the motor current.

Features Of Rare-Earth Permanent Magnet Motors

The rotor pole of the rare earth permanent magnet motor is composed of rare earth permanent magnet steel, so there is no slip, no excitation current, and the rotor has no fundamental wave iron and copper wear.

The rotor is excited by permanent magnets, and no reactive excitation current is needed. Therefore, the power factor is improved, the reactive power is reduced, the stator current is greatly reduced, and the stator copper and iron losses are greatly reduced.

At the same time, because the polar arc coefficient of the rare earth permanent magnet motor is larger than that of the asynchronous motor when the voltage and the stator structure are constant, the average magnetic induction intensity of the motor is smaller than that of the asynchronous motor and the iron loss is small.

Therefore, it can be said that the rare earth permanent magnet synchronous motor is energy-saving by reducing its own losses, and is not affected by changes in operating conditions, environment, and other factors.

Enneng motors are designed to operate with high power density, high efficiency, and lower operating temperatures.

This leads to lower energy consumption
Extended bearing life and lower maintenance costs
Reduced downtime and improved reliability
Resulting in long service life