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Magnet Wire is the core material that supports the stable operation of motors, which are widely used in various fields as the core equipment for converting electrical energy into mechanical energy. Unlike ordinary insulated wires, Magnet Wires combine the advantages of thin insulation and high conductivity to meet the special needs of motor windings. In this article, we will analyze the core reasons, types and applications of Magnet Wire used in electric motors from multiple dimensions to provide reference for relevant practitioners.
Magnet Wire, also known as electromagnetic wire, is a motor and other electromagnetic equipment winding special insulated wire, the core structure of the conductor and insulating coating, both excellent conductive and insulating properties, the insulation layer is thinner, more adaptable to meet the motor intensive winding, high temperature work requirements.
Magnet Wire consists of a conductor and an insulating coating: the conductor is responsible for the conduction of electrical energy, the insulating coating insulates the neighboring conductors from short circuits and protects the conductor from the environment, and the two work in tandem to ensure the normal operation of the motor.
The conductor is mainly copper and aluminum: copper conductor has high electrical conductivity (about 1.7μΩ-cm), excellent thermal conductivity, high mechanical strength, and the purity needs to be ≥99.95%, which is the most widely used; the aluminum conductor is low-cost and lightweight, but has low electrical conductivity (about 2.8μΩ-cm), which is suitable for scenarios that do not have high requirements for efficiency. Insulation coating commonly used polyester, polyurethane, polyimide, etc., suitable for different working environments.
Magnet Wires have advantages in many aspects that ordinary wires cannot match, and are perfectly suited to the needs of electric motors, the core reasons are as follows:
The conductor is mainly made of copper and aluminum, the copper conductor has high conductivity and low loss (in accordance with Joule’s law), the performance is more stable after annealing treatment, and the insulating coating doesn’t affect the conductivity, which is far better than the ordinary insulated wires, and it can improve the efficiency of the motor and reduce the waste of electric energy.
Insulation layer is thin (a few microns to tens of microns) and dense, high dielectric strength, high temperature resistance, aging resistance, can be adapted to the winding of the dense winding to prevent short-circuit; ordinary insulated wires with thick coating, easy to age, can not meet the demand.
The working temperature of motor winding is 80℃-220℃, Magnet Wire is categorized into B grade (130℃), F grade (155℃), H grade (180℃), C grade (above 200℃) according to insulating materials, with high melting point of the conductor, it can work stably under high temperature, while ordinary conductors are poor in heat-resistance and easy to be broken and short-circuited.
Thin insulation layer, small overall diameter, more turns can be wound in the same space to enhance power density; flat Magnet Wire can further improve space utilization, suitable for electric vehicles and other volume- and weight-sensitive scenarios.
Copper conductor has good ductility, good flexibility of the insulating layer, can be repeatedly bent and wound without breakage or damage, suitable for complex winding process, better than ordinary insulated wires.
Although the price of a single meter is slightly higher, but the high utilization rate of materials, long service life (10-30 years), can reduce the motor maintenance and electrical energy costs, long-term comprehensive benefit is better than ordinary wire.
There are significant differences in the working environment, power level, and operating requirements of different motors, and the demand for core indicators such as heat resistance, insulation, solderability, and mechanical properties of Magnet Wires also varies. In order to adapt to the individual needs of various types of motors, the industry has formed a variety of special Magnet Wire types, the following focuses on the four most commonly used, the most widely used Magnet Wire, including its core performance, key parameters, applicable scenarios and advantages of the use of motor selection to provide accurate reference.
Polyester Magnet Wire is currently the most widely used, the most cost-effective basic Magnet Wire, the core insulating material for the polyester resin, the insulation layer is dense and uniform, the thickness is usually between 8μm-25μm, the dielectric strength of up to 40kV/mm-50kV/mm, the insulation reliability. Its heat-resistant grade is mainly divided into class B (130℃) and class F (155℃), which can meet the needs of most low and medium temperature scenarios; excellent mechanical flexibility, can be repeatedly bending, winding without cracking and shedding of the insulation layer, which facilitates the complex winding process of the motor winding. The outstanding advantage of this type of Magnet Wire is cost-effective, low production costs, and wear-resistant, anti-aging performance is better, can adapt to the erosion of the conventional working environment; shortcomings are chemical resistance in general, should not be used for strong corrosion, high humidity in harsh environments, and long term in the high temperature (more than 155 ℃) environment will accelerate the aging of the insulation layer.
Applicable motors: mainly suitable for ordinary household motors and small industrial motors with small power, moderate working temperature and sensitive to cost. In household scenarios, they are widely used in the drive motors of electric fans, washing machines, refrigerators, soybean milk machines, vacuum cleaners and other common household appliances, which can meet the stability and safety requirements of daily use; in industrial scenarios, they are suitable for small pumps, small blowers, light machine tool auxiliary motors and so on, and the power of this kind of motors is usually between 1kW-10kW, and the working temperature can be controlled at 80℃-120℃, which do not need to withstand extreme environmental tests. Polyester Magnet Wire can be perfectly adapted to the needs of these motors, and at the same time effectively control the cost of motor production.
Polyurethane Magnet Wire takes polyurethane resin as the core insulating material, the most prominent advantage is the excellent weldability, no need to remove the insulating layer in advance, through high temperature welding to realize the connection between the winding and the lead wire, which greatly simplifies the motor production process, improves the production efficiency, and reduces the labor cost. The thickness of the insulation layer is relatively thin, usually in 5μm-20μm, dielectric strength up to 35kV/mm-45kV/mm, high frequency performance, high frequency current loss is small, suitable for high frequency motor use. Heat resistance grade mainly B (130 ℃) and F (155 ℃), heat resistance is in the middle level, can meet the needs of conventional low and medium temperature scenes. The disadvantage is that the humidity resistance and chemical resistance is poor, long-term in a humid environment or contact with chemical reagents in the scene, the insulation layer is easy to aging, breakage, so it is not suitable for outdoor, humid or chemical environments.
Applicable motors: Mainly suitable for small motors that need to weld windings and run at high frequency, especially suitable for motors with small volume, compact structure and large production batch. Typical applications include stepping motors, printer motors, photocopier motors, miniature fan motors, audio motors, etc. These motors are usually small in power (≤5kW), high in operating frequency, and the winding connections need to be efficiently welded, so that the weldability and high-frequency performance of the polyurethane Magnet Wires can give full play to their advantages. In addition, some small DC motors, instrumentation built-in motors will also choose this type of Magnet Wire, taking into account the production efficiency and operational stability.
Characteristics: Polyimide Magnet Wire is a representative of high-end high-temperature resistant Magnet Wire, the core insulating material is polyimide resin, with strong heat resistance, heat-resistant grade up to H (180 ℃) and C (200 ℃ and above), long-term operation at 200 ℃ in high temperature environment can still maintain stable insulation properties, short-term overload temperature can reach 220 ℃ -250 ℃. The insulation layer is dense and resistant to high temperature and chemical corrosion, the dielectric strength is as high as 60kV/mm-80kV/mm, which can withstand high-voltage impacts and prevent short-circuiting of the windings; at the same time, it has excellent mechanical strength and aging resistance, and its service life can be up to 20-30 years, which is much higher than that of ordinary Magnet Wire. The shortcoming of this type of Magnet Wire is the high production cost, the price is about 2-3 times of polyester Magnet Wire, mainly used in high-end scenes with very high performance requirements.
Applicable motors: Mainly suitable for high temperature, high pressure, harsh environment of high-end motors, especially suitable for the reliability and service life of the requirements of the very high scenarios. Typical applications include electric vehicle drive motors (operating temperature 150℃-220℃), high-pressure industrial motors (power>100kW, operating temperature 150℃-180℃), aerospace motors, nuclear motors, and high-temperature fan motors. This kind of motor running load, harsh working environment, ordinary Magnet Wire can not withstand high temperature, high pressure test, polyimide Magnet Wire of excellent performance can ensure the long-term stable operation of the motor, reduce the failure and maintenance costs, is the core of high-end motor materials.
Characteristics: The core advantage of self-adhesive Magnet Wire is that it is self-adhesive, with a special self-adhesive coating on the surface of its insulating layer. After the winding is completed, self-adhesive fixing of the winding coils can be realized through heating (usually 80℃-120℃), which can greatly simplify the production process of the winding without the need for additional adhesives, and at the same time, reduce the influence of adhesives on the performance of the motor. Its insulation performance is on a par with that of ordinary Magnet Wires, and depending on the insulating material, the heat-resistant grade can cover Class B (130℃), Class F (155℃) and Class H (180℃). It has high mechanical strength, and the stability of the winding is good after fixing, and it is not easy to be loosened due to the vibration of the motor. The disadvantage is that the scope of application is narrower, mainly for small and micro motors, and the moisture resistance of the self-adhesive coating is slightly poor, and should not be used in long-term humid environments.
Applicable motors: mainly suitable for small, miniature, high-speed running motors, these motors are small in size and have dense windings, which require high stability and compactness of the windings. Typical applications include miniature DC motors, stepper motors, high-speed fan motors, instrumentation built-in motors, small generators, etc. They are especially suitable for miniature motors that require rapid mass production and have complex winding structures. For example, micro DC motors are commonly used in smart wearable devices, small electronic instruments, the winding volume is very small, the use of self-adhesive Magnet Wire can be realized tightly wound and firmly fixed to ensure the stability of the motor when running at high speed.
Magnet Wire performance directly determines the motor efficiency, heat dissipation, life, energy consumption and other core indicators, the specific impact is as follows:
The higher the conductivity, the smaller the copper loss, the higher the efficiency; high space utilization, more turns of the winding, strong magnetic field, less power input under the same power, higher efficiency. Poor insulation will increase losses and reduce efficiency.
Insulation thermal conductivity, winding density affects heat dissipation: polyimide insulation thermal conductivity is excellent, thin coating facilitates heat transfer; dense winding to increase the contact area of heat dissipation, but need to cooperate with the heat dissipation system to balance the effect of copper conductor heat dissipation is better than aluminum.
The higher the heat resistance level, the slower the aging of the insulation layer, the longer the life span; good insulation performance can avoid short circuit, strong mechanical flexibility can withstand the operating stress, both can extend the life of the motor.
Copper loss accounts for 40%-60% of the total loss of the motor, Magnet Wire, high conductivity, wire diameter, winding dense, can reduce copper loss; good insulation can reduce leakage loss, low dielectric loss can reduce the waste of electrical energy, thereby reducing energy consumption.
Different motors have different working environments and performance requirements, the Magnet Wire selection varies significantly, and the core applications are as follows:
Working temperature 150℃-220℃, need high power, small volume, mainly using polyimide Magnet Wire (heat-resistant, excellent insulation) and flat copper Magnet Wire (high space utilization, good heat dissipation), suitable for power and energy-saving needs.
Large power, complex environment, small (<10kW) with polyester Magnet Wire, medium-sized (10-100kW) with polyesterimide Magnet Wire, large (>100kW) with polyimide Magnet Wire, chemical corrosion-resistant models for harsh environments.
Small power, cost-sensitive, commonly used polyester Magnet Wire (electric fans, washing machines), polyurethane Magnet Wire (microwave oven motors), self-adhesive Magnet Wire (miniature fans), adapted to the different production and use of demand.
Operating temperature 80℃-150℃, diverse environments, polyesterimide/polyimide Magnet Wires for compressor motors, polyester Magnet Wires for fan motors, moisture and corrosion resistant models for circulating pump motors.
The world’s leading Magnet Wire standards are NEMA MW1000 and IEC 60317, which, in conjunction with temperature rating standards, regulate the quality and application of Magnet Wire.
The authoritative U.S. standard specifies the technical requirements for Magnet Wire conductors and insulation materials, provides detailed test methods, and divides the quality into grades, which meets the needs of North American motor applications and emphasizes practicality and reliability.
International general standard, covering the Magnet Wire classification, technical indicators, test methods, suitable for most countries around the world, China’s industry standards reference to the development of this standard, strong generality.
The core of selection centers around four dimensions, combining the needs of the motor and industry standards to ensure the suitability:
Low voltage (≤500V) choose polyester/polyurethane Magnet Wire, medium voltage (500V-1000V) choose polyesterimide Magnet Wire, high voltage (>1000V) choose polyimide/composite insulated Magnet Wire, the rated voltage needs to be higher than the working voltage 1.2-1.5 times.
According to the maximum working temperature of the motor winding, select the Magnet Wire which is 10-20℃ higher than it, taking into account the performance and cost, avoiding waste.
Wire diameter is positively correlated with current-carrying capacity, need to match the rated current of the motor, balance the copper loss, motor size and cost, refer to AWG wire gauge selection.
Magnet Wire is the core material of motor winding, its excellent conductivity, insulation, heat resistance and other properties, perfectly suited to the needs of dense winding, high temperature operation of the motor, is the key carrier of electrical energy to mechanical energy. Different types of Magnet Wire are suitable for different motor scenarios, and the selection should be based on the combination of voltage, temperature, scenarios and other factors, with reference to authoritative standards. With the upgrading of motor technology, Magnet Wire will continue to innovate and help improve motor efficiency and reliability.
