Design of Power Supply and Electric Control Equipment for Ferrous Alloy Electric Furnace
Abstract
Ferrous alloy electric furnace is a kind of metal melting device for industrial use, which needs to work safely and reliably under various conditions. This article introduces some principles of the power supply and electric control equipment design for ferrous alloy electric furnace, including the selection of power supply, power supply design, and electric control equipment selection. The design of these components has greatly improved the safety and stability of the system.
1 Introduction
Ferrous alloy electric furnace is a kind of important and widely used metallurgical equipment. It has the characteristics of good thermal and electrical insulation, high temperature melting, and convenience in control. Due to the high temperature and high pressure operation in the molten metal, it is important to ensure the reliability and safety of the power supply, power supply design and electric control equipment design of ferrous alloy electric furnace.
2 Selection of Power Supply
The power supply of ferrous alloy electric furnace is mostly composed of AC power and DC power. The AC power is from single-phase 35V, 10A (for example: 3KW-5KW) to three-phase 380V, 180A (for example: 50KW-100KW).
The selection of AC power needs to pay attention to the following points:
A. Voltage range. The AC voltage shall be selected regularly, and the voltage fluctuation shall not exceed 5% of the rated value.
B. Overvoltage protection. Using a fuse with overvoltage protection is required.
C. Overload protection. The protection range shall be set at 65%-130% of rated current.
D. Leakage protection. The earth leakage circuit breaker should be installed properly.
E. Phase imbalance protection. It is necessary to install phase sequence protection and phase failure protection.
The DC power is usually provided by a power supply unit. The performance requirements should be as follows:
A. Stable output voltage. The output voltage shall be adjusted stably.
B. Overvoltage and overcurrent protection. It is necessary to use the corresponding overvoltage protection and overcurrent protection in order to ensure the safe operation of the power supply unit.
C. Insulation and leakage resistance. The insulation of the power supply unit should meet the requirements of secondary insulation, and the leakage resistance should be larger than 9MΩ.
3 Power Supply Design
The design of the power supply should be based on the voltage, current, heating power and working time of the ferrous alloy electric furnace.
A. The static electricity of the furnace shall be less than 20V, and the dynamic electricity shall be allowed to rise to the maximum for a short time.
B. The power supply line shall be designed separately for AC and DC power.
C. The sectional area of the power supply line should be selected according to the working current of the furnace, and the power supply line should be designed as straight line.
D. The power supply line should be designed separately for the control circuit and the heating power circuit.
E. It is necessary to set up overvoltage protection and overcurrent protection devices on the power supply line.
4 Electric Control Equipment Selection
The electric control equipment of ferrous alloy electric furnace is mainly composed of control transformer, contactor and thermal relay.
A. Control transformer:
This is used to control the current of the furnace. Generally, a CT with a ratio of 1 is suitable. The current value should be close to the rated current of the furnace.
B. Contactor:
This is used to connect the power supply and disconnect it when necessary. It is usually used together with the thermal relay. The degree of protection of the contactor should be IP20.
C. Thermal relay:
This is used to detect the overheating of the furnace and disconnect it when necessary. The action frame should match the three-phase contactor.
Conclusion
The design of power supply and electric control for ferrous alloy electric furnace is very important for the safety and reliability of the system. This article has discussed some principles of the design, such as the selection of power supply, power supply design and electric control equipment selection, which have greatly improved the safety and stability of the system.
