Application of industrial UPS in automobile welding robot anti electric shock (2/3)

We know that no matter how much the power supply bureau spends to improve the power grid, it still can not avoid the occurrence of voltage sag or rise, voltage surge, harmonic interference, frequency drift, transient peak / high voltage, power outage and other power quality problems, which will bring adverse effects to power users. This is because there are a large number of loads on the power grid, some of their working state and fault state, as well as natural disasters, will affect the security and reliability of the power grid. Such as: lightning and rainstorm, strong wind and snow, misoperation of crane and excavator personnel in construction, animal contact line, other large motor starting, short circuit fault, line switching power distribution device fault, etc.

According to statistics, the voltage sag ranges from 70% to 90% of the rated value (residual voltage), and the typical duration is 10ms-1s. The number of sags encountered by each user in a year varies from more than ten times to hundreds of times. Among all kinds of power quality problems, voltage sag is the most important factor that causes abnormal operation or shutdown of electrical equipment. According to EPRI statistics, more than 90% of power quality events are voltage sags. Voltage sag has the characteristics of high frequency of occurrence and the cause of accident is not easy to detect.

The concept of "shaking electricity"

Voltage sag (voltage sag; voltage dip), commonly known as "power swing", refers to the sudden event that the effective value of power supply voltage suddenly drops sharply and returns to normal in a short period of time. Voltage sag is also known as voltage sag, voltage sag, transient voltage fluctuation and voltage sag in China. Most of them are caused by lightning strike, short circuit, heavy load starting, etc., and the voltage of power supply drops sharply or the voltage is interrupted for several seconds for a short time, resulting in the failure of electrical equipment. The amplitude, duration and frequency of voltage sag are usually used to describe voltage sag, and sometimes the abrupt change of phase is also considered. The International Institute of electrical and Electronic Engineers (IEEE) defines the voltage sag as that the effective value of the supply voltage drops rapidly to 90% - 10% of the rated value, and then recovers to the normal value; while the International Electrotechnical Commission (IEC) defines the voltage sag as falling to 90% - 1% of the rated value with a duration of 10ms-1min.

The harm of "shaking electricity"

Most of the motors are controlled by AC contactor, soft starter and frequency converter. The AC contactor will release and the soft starter and frequency converter will be shut down when the power is shaken. And the shutdown of key units will lead to large units, even the whole production plant chain shutdown, and eventually lead to the continuous production process is forced to interrupt, production units are forced to stop operation, thus causing huge economic losses to enterprises, and sometimes fire, explosion and other vicious accidents occur. Figure 2 shows the causes, effects and consequences of "power swing".

According to the needs of users, we adopt integrated solutions to solve the problems of different voltage levels, different frequency levels and not being monitored by UPS host in different countries in the original split solution, which not only reduces the floor area, improves the availability, but also saves the cost for users. Through the load analysis of the site and the investigation of the site environment, adhere to the method of "high engineering modularization" and comply with the "industry 4.0" principle. We should carry forward the "craftsman spirit" attitude, overcome difficulties, redesign and adjust the electrical parameters of some components in UPS system, and provide customized solutions for users on time. The solution has many advantages, such as strong stability, high reliability and strong expansion. It meets the special requirements of user protection level, simple system architecture, simple operation and system reliability, and ensures that UPS can continuously provide high reliable UPS power supply under the condition of power supply system outage.

After replacing the imported robot regulated power supply with industrial UPS, it has been running well for two years without any emergency repair, which is highly praised by users.

(From magazine UPS Application - November 7 2017)

About AVIC-Tech

AVIC-Tech (Xiamen)Electric Power Technology Co.,Ltd is a high-tech enterprise specializing in R&D, manufacture, sales and service of high-end power supply. Our flagship products are industrial UPS (1kVA-800kVA), dynamic voltage restorer (10kVA-3150kVA), and lithium battery system, which are widely used in nuclear power, electric power, petroleum and petrochemical, rail transportation, industrial manufacturing and other fields.

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