Overview of constant voltage transformer
Writer： Hengfeng you electric Time：2023-05-09 views：times
1、 Principle of constant voltage transformer:
Constant voltage transformer is also called magnetic saturation regulator.
The constant voltage transformer adopts a "day" shaped iron core, the primary coil is in one window hole, the secondary coil and resonance coil are in another window hole. The resonant coil is externally connected with a resonant circuit whose resonant frequency is close to the power frequency.
When the primary is powered on, the resonant circuit vibrates to make the secondary iron core shallow saturated and form a constant alternating magnetic field. Its magnetic induction intensity is within a certain range and is basically not affected by the change of input voltage, so the induced electromotive force of the secondary coil remains unchanged. In this case, the primary input current only serves to supplement energy.
The output voltage of constant voltage transformer is only related to the magnetic parameters and cross-sectional area of iron core, and has nothing to do with the ratio of primary and secondary turns.
The efficiency, volume and weight of constant voltage transformer are equivalent to those of ordinary transformer. When the iron core material is better and the mains voltage changes between 160-250 volts, the change of output voltage is less than 1.5%; When the load current is reduced from full load to half, the output voltage changes by about 1.5-4%. When the output is short circuited, the output current increases by about one time, so it is not afraid of short circuit for a long time.
Constant voltage transformer integrates voltage stabilization, isolation and voltage transformation. It has two-way filtering function, which can eliminate the interference of power grid clutter. It has good anti-interference ability. The output is sine wave or quasi square wave.
2、 What is a constant voltage transformer
Constant voltage transformer is an ideal regulated power supply for precision electronic instruments, microcomputers and CNC equipment. There is a "day" shaped iron core in the constant voltage transformer. The primary coil is in one window hole, and the secondary coil and resonance coil are in another window hole. The resonant coil is externally connected with a resonant circuit whose resonant frequency is close to the power frequency.
When the primary power supply is connected, the resonant circuit vibrates to make the secondary iron core shallow saturated and form a constant alternating magnetic field. Its magnetic induction intensity is within a certain range and is basically not affected by the change of input voltage, so the induced electromotive force of the secondary coil remains unchanged. In this case, the primary input current only serves to supplement energy.
A stable DC power supply circuit is needed in instruments and devices. With the development of science and technology, the requirements for DC stability are higher and higher, which brings difficulties to the design and development of power supply. Constant voltage transformer is suitable for power supply devices with high stability requirements. It first makes the AC power frequency power supply as the first step of AC voltage stabilization, and the stability range can be about 1%, and then through rectification and DC linear series voltage stabilization, the power supply is easier to meet the requirements of high stability. In the electrical equipment with low stability requirements, the DC linear voltage stabilizing part can be omitted by directly reducing and rectifying with a constant voltage transformer, and the stable voltage of various outputs can be obtained, and the stable range can be within ± 3 g. Because of its simple structure, easy manufacture and low cost, constant voltage transformer will be widely used in electrical equipment. In areas with large changes in grid voltage, it can withstand a wide range of changes, and the output is constant, which has practical value.
3、 Characteristics of constant voltage transformer
a. Strong anti-interference ability, common mode suppression ≥ 50dB, can eliminate power grid clutter, which is sine wave or method waveform.
b. The output neutral line can be directly connected to the earth wire, because there is no electrical connection between the output and the input.
c. Harmonic suppression: it can obviously suppress the 3rd ~ 7th harmonic, especially the elimination rate of the third harmonic is more than 90 [[%]].
d. The working components are only transformers and capacitors, and the reliability of the whole machine is very high.
e. When the output voltage drops to zero in case of overload or short circuit, it will automatically limit the current, which is 1.5 ~ 2.5 times of the rated value. It will recover automatically after the fault is eliminated, and the regulated power supply will not be damaged.
4、 Constant voltage transformer action
a. Places where the altitude is not more than 1000m and the surrounding medium temperature is not higher than 40 ℃ and not lower than - 40 ℃. If the above normal use conditions are exceeded, the corresponding quota adjustment shall be made according to the national standard gb6450-86.
b. The relative humidity of the air shall not be greater than 85 [%] (when the temperature is 20 ℃± 5 ℃).
c. Places without violent vibration and turbulence and with a vertical inclination of no more than 5 ℃.
d. There is no conductive dust and corrosive gas or vapor that can damage metal and insulation.
e. Places where fire, explosion and danger cannot occur.