18 LED tube detection PF value distribution example diagram We adopt the advanced technology imported from Europe, patented technology, specialized software to optimize the design for 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. Dry Type Transformer Dry Type Transformer,High Quality Special Transformer,1600Kva Dry-Type Transformer,800Kva Dry-Type Transformer Hangzhou Qiantang River Electric Group Co., Ltd.(QRE) , https://www.qretransformer.com
Too low a power factor will reduce the utilization of the equipment and increase the power loss of the line. The US Energy Star (DLC) requires LED tube (V2.1) PF ≥ 0.9, considering the tolerance ≥ 0.87.
The number of LED tubes used by ordinary consumers is limited, so the power factor has little substantial impact on the average family, and it is often easily overlooked. Some luminaire manufacturers have also drilled holes and will not increase the power factor.
The results of 18 LED tube inspections of 15 brands tested by CLEAR show that there are only 3 samples in compliance with the DLC standard (PF≥0.9, considering the tolerance ≥0.87), and the coincidence rate is only 16.7%. Among them, the highest measured PF value is PZ-DG-T 8-002 of Puzhong Lighting, reaching 0.9728; the lowest PF value is T5 fluorescent lamp of Nikko Lighting, only 0.3944; most of the PF values ​​of other products are around 0.5 . 
Especially in lighting products such as lamps, generally adopting linear ICs with high-resistance and step-down voltage, high-voltage constant current ICs, etc., the power factor is about 0.5, and the light efficiency can also be very high. Coupled with the blind spot of consumer perception, LED lamps with linear constant current power supply are very common in China, but it is difficult to pass some testing and certification in overseas markets.
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[Text / high-tech LED reporter Zhu Chunwei] In the AC circuit, the cosine of the phase difference between voltage and current is called power factor (PF), the size is related to the load nature of the circuit, so the closer the power factor is to the 1st lamp. The power factor of a resistive load such as an incandescent bulb or an electric resistance furnace is 1, and the power factor of a circuit generally having an inductive load is less than one.