Harmonics have many very harmful effects on electronic equipment. A common symptom of harmonics is overheating wires and furnace transformers, causing circuit breakers to trip when they shouldn't. Harmonics are classified by name, frequency and order. The name usually refers to whether the harmonic is the second, third, fourth, etc. of the fundamental frequency. Frequency refers to the operating frequency of harmonics, the second harmonic operates at 120 Hz, the third harmonic operates at .80H:, the fourth harmonic operates at 240H:, and so on. Sequence refers to the phase sequence associated with the fundamental wave. In an induction motor, the positive phase sequence harmonics rotate in the same direction as the fundamental frequency; the negative phase sequence harmonics rotate in the opposite direction to the fundamental frequency.

Positive phase sequence harmonics are usually caused by overheating of conductors, transformers, and circuit breakers. In addition to motor problems, negative phase sequence harmonics can cause the same heating problems as positive phase sequence harmonics. Since the phase rotation of negative phase sequence harmonics is opposite to the phase of the fundamental frequency, it tends to weaken the rotating magnetic field of the induction motor, causing the motor to produce less torque. The reduction in torque causes the motor to operate at lower than normal speeds. Reduced speed causes overcurrent and overheating of the motor.

A harmonic transformer is a power transformer that can effectively suppress harmonics in the power system, thereby improving the efficiency and stability of the power system.

The frequency range of the resonant transformer is 1~50kHz. It can be used with medium frequency electric furnace, medium frequency power supply and super audio power supply. It is used for heat penetration of workpieces, quenching and annealing of metal workpieces, medium frequency variable tube heating and metal diffusion. Type welding [brazing] and other process equipment.

The multi-turn ratio medium frequency transformer core is made of 0.27-0.3mm oriented high magnetic permeability cold-rolled silicon steel sheets, which are processed and assembled using special processes. The primary turns ratio is up to 23 turns, which can also be changed according to different capacities and frequencies. Resonant transformers are cooled by water cooling.

The resonant transformer uses the principle of series resonance or parallel resonance to generate large current and high voltage. Generally used for large capacitive or large inductive loads. Using the parallel resonance of the load and the equipment, a larger load current can be obtained with a smaller excitation current; using the series resonance of the load and the equipment, a higher voltage can be obtained on the load with a lower excitation voltage. The basic formula of the resonant transformer is ω=1/√(LC), where ω is the angular frequency of the power supply

=2лf, L and C are the inductance and capacitance of the load or device. To fully satisfy the equation, at least one parameter among ω, L, and C must be adjustable. In order to meet the requirements of the output voltage or current, one of L and C must be adjustable. In order to accurately find the resonance point, it is also necessary to The required parameters can be fine-tuned steplessly. Therefore, modern resonant transformers generally use variable frequency power supply as the power supply in order to adjust ω, and use a tapped reactor as L, and in conjunction with C, the resonance point can be easily found.

The impact of harmonics on transformers

When harmonic current flows through the transformer, it will cause the transformer to emit additional heat

Harmonics will affect the actual capacity of the transformer. Reduce

Excessive harmonic current will shorten the life of the transformer

Harmonics increase the resistance loss of the coil winding (called copper loss) and the loss of the iron core (called iron loss)