Why is the Output Voltage of Transformers 400V?
By observation, we can see that most power transformers have a secondary output voltage of 400V, while the rated voltage of electrical motors is typically 380V. Why is there a discrepancy between these two voltages? Let’s explore the reasons:
First, we need to understand the phenomenon of voltage drop. The 400V voltage on the low-voltage side of the transformer is the no-load voltage, not the operating voltage under load. When the transformer is loaded, the actual output voltage decreases—this is known as voltage drop or voltage regulation.
According to national standards, under conditions of 0.8 power factor and 100% load, the voltage regulation of transformers is approximately 5%. Therefore, for systems designed for 380V operation, the no-load voltage on the secondary side of the transformer is specified as 400V.
Besides voltage drop, setting the voltage to 400V is also related to the design and operation of the power system. Key influences include:
- System Stability: A 400V output provides a wider voltage adjustment range, helping to maintain the stability of the power system.
- Equipment Safety: If the low-voltage side voltage is lower than 380V, the output voltage will be even lower. Electrical devices are designed for specific voltage levels. Lower output voltages may cause some equipment to operate improperly or even sustain damage.
- Economic Efficiency: Higher voltage levels generally reduce operational and maintenance costs. Choosing a 400V output helps lower the operational and maintenance expenses of the power system.
- Growing Power Needs: As electricity demand increases, the grid must provide greater capacity and improved power supply. Raising the low-side voltage enables the delivery of more power without modifying existing equipment.
About Shenzhen Shentebian Electric Equipment Co., Ltd.
Shenzhen Shentebian Electric Equipment Co., Ltd., a wholly-owned subsidiary of the Jishengchang Group, was founded in 2004. With its own industrial park, the company is a technologically advanced and robust manufacturer specializing in transformers. It is one of the earliest enterprises in Shenzhen to enter the power transformer manufacturing sector. STB is the transformer brand under Shenzhen Shentebian Electric Equipment Co., Ltd.
