Structural performance and application guide for toroidal transformers

The toroidal transformer has the advantages of small size, low noise, low heat generation and high conversion efficiency. It has been increasingly used in industrial automation equipment, instrumentation, petrochemical, medical and health, agricultural production, mechanical processing, scientific research, military, and household. Electrical appliances, etc. Toroidal transformers, especially in the application of stepper motor power supplies, have shown excellent performance, far exceeding the performance of U-type and E-type transformers. The following is a brief introduction to the performance and application of toroidal transformers.

Industrial application of toroidal transformer

Optional toroidal transformer, according to the load voltage, current usage, to determine the power of the toroidal transformer. The toroidal transformer loses the current and is the output current at full load. When overloaded, the toroidal transformer can output more than 30% of the rated current. Although the toroidal transformer has a good overload capability, it is required to pay attention to the following two aspects:

1, applied to start overloaded equipment

Some devices operate at rated currents, and the current at start-up is very large, sometimes exceeding 30% to 50% of the rated current. For example, the overload capability of an AC servo motor is typically designed to be three times the rated operating current. When the load starts, the current is large, and the toroidal transformer needs to be overloaded for a short time. Such a device that drives current overload, configured with a toroidal transformer, needs to consider about 20% of the current output current of the transformer. Because of frequent starting overload work, the temperature of the toroidal transformer will rise, which will shorten the life of the transformer for a long time.

2, applied to equipment without overload

Many devices are designed with maximum operating current in mind and no need to overload the starting current. For example, a stepper motor is used as the power of the device, and the operating current is the same as the starting current. When the toroidal transformer is selected, as long as the output current is equal to the maximum current of the stepper motor driver or is greater than about 10%, it is not necessary to design the margin of the output current of the toroidal transformer to be large. The stepper motor never experiences an overload current. In more work environments, the power of the stepper motor is variable. This requires confirmation of the voltage and current parameters during structural design, artificially given a reasonable power consumption. In fact, the power consumption of the stepper motor decreases as the speed increases. The stepper motor is equipped with a toroidal transformer, which is the most hobby choice.

Structural performance of toroidal transformer

It has been found that the coil eddy current loss (iron loss) wound by the toroidal core is minimized, and the core of the transformer is machined into a ring shape. The core of the toroidal transformer is made of cold-rolled silicon steel sheets having a thickness of 0.35 mm or less and seamlessly wound into a shape. The coil is evenly wound around the core, and the direction of the magnetic line generated by the coil is almost completely coincident with the magnetic circuit of the core, so that the eddy current loss generated by the alternating current through the coil is minimized. The core loss of the U-type and E-type transformers is reduced by more than 50%, thereby improving the conversion efficiency of the transformer or the isolation.

The core of the toroidal transformer can be processed to the extent of no air gap, the stacking factor can be as high as 95% or more, and the core magnetic permeability can be 1.5 to 1.8T (the laminated core can only take about 1.2T or lower), so the toroidal transformer The electrical conversion efficiency can reach more than 95%. The airless structure of the toroidal transformer core enables the no-load current to be very small, and there is no heat generation under long-term energization.

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

Since the core has no air gap, the magnetic permeability is high and there is no vibration noise of the physical structure. Even in high-current, high-load operating environments, human hearing cannot be felt to be noisy. The outline drawing of the toroidal transformer is as follows:

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

The toroidal transformer power is usually determined by its diameter and height. The higher the power, the corresponding increase in volume and weight. Various power specifications, various input and output voltage configurations are very flexible, and the processing equipment is simple and fast.

The full-load operation of the toroidal transformer is only 40 °C, allowing short-time overload operation. The primary and secondary windings are insulated with a grade B (130 ° C) polyester film and can withstand a 4000 V, 1 minute withstand voltage test.