description:
The excitation method is to output the pulse wave by the IC, and the oscillator inside the IC starts to vibrate, and the self-excited type is the free oscillation of the feedback signal through the oscillation tube.
The self-excited frequency cannot be fixed. This is the frequency modulation characteristic of this RCC circuit, which varies due to load changes. Self-oscillation state of switching power supply
After the power is turned on, the alternating current is rectified and filtered, and the first pass is applied to the drain (D pole) of the switch Q2 through the transformer primary, and the other is applied to the Q2 gate (G pole) through the start resistors R2 and R3, thereby turning on the switch Q2. After conduction, the primary side of the transformer T1 generates an induced electromotive force that is up, down, and negative (1 positive and negative). Due to the mutual inductance, the T1 auxiliary winding also generates a corresponding induced positive electromotive force of positive and negative (3 positive and negative). Thus, T1 The positive pulse voltage on pin 3 is applied between G and S of Q2 through C5 and R5, so that the drain current of Q2 is further increased, so that switch Q2 quickly enters saturation under the action of positive feedback avalanche process. During the saturation of the switching tube, the rectifying and filtering circuit connected to the secondary winding of the switching transformer T1 is turned off due to the reverse of the induced electromotive force, and the electric energy is stored in the form of magnetic energy inside the T1 primary winding. Due to the extremely short time of the positive feedback avalanche process, timing Capacitor C5 can't be charged (it is equivalent to short circuit). After Q2 enters saturation state, the induced voltage on the auxiliary winding charges C5. As C5 charge continues, the potential difference between the two ends rises, so Q2 gate potential Will lower, thus causing Q2 to exit saturation, when Q2 After the saturation state, the internal resistance increases, causing the drain current to further decrease. Since the current in the inductor cannot be abruptly inverted by the induced electromotive force of each winding of the switching transformer T1, the negative pulse voltage of the auxiliary winding 3 and the timing capacitor C5 are After the charging voltage is superimposed, Q2 is quickly cut off.
During the off period of the switch Q2, the timing capacitor is discharged to provide a circuit for the lower positive feedback voltage (drive voltage) to ensure that the switch Q2 can enter the saturation state again, and the energy stored in the primary winding of the switching transformer T1 is coupled to the secondary winding. After being rectified by the rectifier, the energy is supplied to the filter capacitor. When the energy of the primary winding drops to a certain value, according to the principle that the current in the inductor cannot be abrupt, the primary winding generates an anti-lead electromotive force to resist the drop of the current. The current produces a positive and negative induced electromotive force in the primary winding of T1. The 3-pin induced and positive pulse voltage of T1 passes through the positive feedback loop, causing the switching transistor Q2 to be turned back on. Therefore, the switching power supply operates in a self-oscillating state. Therefore, The on-time of the RCC circuit is also the charging time of the C5 capacitor, and the turn-off time is also the discharge time of the C5 capacitor!
We adopt the advanced technology imported from Europe, patented technology, specialized software to optimize the design for33kV cast resin Dry Type Transformer. The core is made of cold-rolled grain-oriented silicon steel sheet which cut in step-lap by GEORG Germany TBA core cutting lines and laminated by the method of fifth-order step-by-step stacking technology, enabling the no-load performance of the core to improve greatly. The epoxy resin from American HUNTSMAN is adopted for the windings which casted in the vacuum resin casting machine imported from HEDRICH, Germany. The winding material ensures good permeability, no bubbles occur, which leads to minimum partial discharge. The HV and LV winding mate with each other tightly, which ensures solid strength of structure and capability to withstand short circuit and vibration. Under normal service condition, the service life of dry type transformer is 30 years. No crack will form on the surface of transformer winding due to temperature variation as long as the transformer runs under normal service condition.
Earthing Transformer,33Kv Dry Type Transformer,33Kv Transformer,33Kv Cast-Resin Transformer
Hangzhou Qiantang River Electric Group Co., Ltd.(QRE) , https://www.qretransformer.com