Controls for Arc Furnaces using VBU* Switches
|VBU Poles per Phase||Control Voltage||Control Part No.|
The control to the left is a direct replacement for a Joslyn* VBU* control. VBU switches shown here can be used at primary voltages of 69 to 145 kV. They can also be used at 34 kV with 2000 and 3000 A modules. The control shown operates two VBU poles per phase, but it can be expanded to operating up to five VBU* poles per phase.
The control is modular in design for easy diagnosis and repair. A person who does not know all the details of the control can diagnose a problems by substitution. The control is connected to the VBU* switch by a cable with a connector on both ends to reduce wiring at installation. An adapter kit is provided to install a receptacle on each VBU pole.
This control can minimize transient in-rush current either with a resistor insertion switch here or by synchronous closing.
The control operates on stored energy for both closing and opening. It is operated by an Allen Bradley™ MicroLogix™ 1100 PLC which has diagnostics built into its program. The control can detect a switch mechanical malfunction and initiate an emergency trip so as to prevent single phasing of the furnace transformer. Single phase power on a furnace transformer is a frequent cause of exploding arrestors.
The control has a reset function which can reset the control following an intermittent switch malfunction. This feature enables a furnace to continue operating without down time while deferring the maintenance on switches to a convenient day.
The MicroLogix™ PLC has an Ethernet connection for remote monitoring with a PanelView™ monitor. The PanelView™ monitor graphically displays individual switch open or closed status and maintains a date and time stamped log of switch malfunctions which resulted in the control being reset.
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