Toroidal Transformer User Guide

Toroidal transformers have the advantages of small size, low noise, low heat generation, and high conversion efficiency. They have been increasingly used in industrial automation equipment, instrumentation, petrochemicals, medical and health, agricultural production, mechanical processing, scientific research, military industry, household appliances, etc. Toroidal transformers, especially in the application of stepper motor power supply, show excellent performance, far exceeding the performance of U-type and E-type transformers. The following briefly introduces the performance and application of toroidal transformers.

Structure and performance of toroidal transformers

People found that the eddy current loss (iron loss) of the coil wound by the toroidal core is the smallest, so the iron core of the transformer is processed into a ring. The iron core of the toroidal transformer is made of cold-rolled silicon steel sheets with a thickness of less than 0.35mm, which are seamlessly rolled into shape. The coil is evenly wound on the iron core, and the direction of the magnetic lines of force generated by the coil is almost completely coincident with the magnetic circuit of the iron core, achieving the minimum eddy current loss generated by the AC passing through the coil. The core loss is reduced by more than 50% compared with the U-type and E-type transformers, thereby improving the conversion efficiency of transformer or isolation.

The core of the toroidal transformer can be processed to the extent of no air gap, the stacking coefficient can be as high as more than 95%, and the core magnetic permeability can be 1.5~1.8T (the laminated core can only be about 1.2T or lower), so the electrical conversion efficiency of the toroidal transformer can reach more than 95%. The airless structure of the toroidal transformer core can make the no-load current very small, and there is no heating phenomenon when powered on for a long time.

The space occupied by the length, width and height of the toroidal transformer is a cylindrical structure, and its volume is about half that of the U-type and E-type. The toroidal transformer. The core has no air gap, the winding is evenly wound on the toroidal core, and the magnetic circulation structure is almost in a closed space, achieving small leakage magnetic field, weak electromagnetic radiation, strong resistance to external magnetic interference, no need to add a shielding layer, and installed on various electronic equipment with complex structures, without any electromagnetic interference.

Because the core has no air gap, the magnetic permeability is high, and there is no vibration noise of the physical structure. Even in a high current and high load operating environment, the human hearing cannot feel the noise.

When the toroidal transformer is loaded and running, its own temperature is very low. Usually, its iron loss can be less than 1W/kg, which is particularly suitable for instruments with narrow heat dissipation space.

The power of a toroidal transformer is usually determined by its diameter and height. The higher the power, the larger the volume and weight. The configuration of various power specifications and various input and output voltages is very flexible, and the processing equipment is simple and fast.

The temperature rise of the toroidal transformer at full load is only 40℃, which can allow short-term overload operation. The primary and secondary windings are insulated with Class B (130℃) polyester film, which can withstand AC 4000V, 1 minute withstand voltage test.

Application of toroidal transformer

When selecting a toroidal transformer, the power of the toroidal transformer should be determined according to the voltage and current usage of the load. The output current of the toroidal transformer is the output current when it is fully loaded. When overloaded, the toroidal transformer can output about 30% greater than the rated current. Although the toroidal transformer has a good overload capacity, it is still required to pay attention to the following two issues:

1. Applicable to equipment with overload at start

The current of some equipment during operation is rated, but the current at start-up is very large, sometimes exceeding the rated current by about 30%~50%. For example, the overload capacity of AC servo motors is usually designed to be three times the rated working current. The current at the start of the load is large, and the toroidal transformer needs to be overloaded for a short time. For such devices with overloaded driving current, when configuring a toroidal transformer, it is necessary to consider that the rated output current of the transformer is about 20% of the rated current of the device. Frequent overload work at the start will cause the temperature of the toroidal transformer to rise, which will shorten the life of the transformer over a long period of time.

2. Application to devices without overload

Many devices are designed with the maximum working current in mind, and the starting current does not need to be overloaded. For example, as the power of the stepper motor, the working current is the same as the starting current. When selecting a toroidal transformer, as long as the output current is equal to the maximum current of the stepper motor driver or greater than about 10%, it is fine. There is no need to design a large margin of the output current of the toroidal transformer. Stepper motors will never have overload current. In more working environments, the power of stepper motors is variable. This requires confirming the parameters of voltage and current during structural design and artificially giving a reasonable power consumption. In fact, the power consumption of stepper motors decreases as the speed increases. It is the best choice to configure a toroidal transformer for stepper motors.