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 145kV. They can also be used at 34kV with 2000 and 3000A 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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