GLD- INDUCTION FURNACE

GROUND LEAK DETECTOR

1) GLD is directing the first earth for the system .G stands for electrical component grounding & LD stands for Leak detector
2) It is the voltage sensing circuit it senses voltage across the DC supply. In case of voltage exceeding 200V,GLD will turnoff the power unit automatically.

GLD due to panel problem
After GLD arrives press reset button and release, when the GLD immediately glows GLD shows After GLD arrives press both reset and probe disconnect button then remove the finger from reset button immediately GLD shows the problem in panel.

GLD due to furnace side
· After GLD arrives press probe disconnect button ma value goes to 0 means GLD due to crucible
· Every GLD failure, we need to check GLD & GFL function.

Test button
This button puts an artificial ground on the ground detector to ensure the functioning properly

GLD Voltage
GLD is a 45v DC unit with continuously changing polarity. It is supplied to the power circuit through choke.
GLD OPTO
It converts AC to DC with every 20seconds polarity change
GLD input power detail
Input -415 / 110V Pin no.100 common & Pin no. 111 = 26V DC
Wire no. 144 for GLD connection in control board +15v Healthy & 0v Faulty
GLD Volt trip
This problem is related to converter section or incoming normal 60-volt supply

GLD Current trip
This indication shows there is a problem in crucible side (metal penetration or scrap touching into coil or water leakage from coil and hose)

Probe disconnect
When pressing this button, it disconnects the crucible side GLD.It is helpful to find whether the GLD is due to Furnace or panel

GLD Indication other than furnace
ü Higher water conductivity increases the electrolysis process of Cu tubes and components, etching away gradually. This may also result in false tripping of GLD
ü Good working furnace GLD should be 5 to 6ma only.
ü Increasing of leakage current cause damaging GLD circuit resulting frequent fault GLD trip. (Leakage current increased due to high water conductivity)

GLD Wire & connection
· Wire should be Stainless steel (304 or 316)
· Thickness of the wire should be 3 to 5mm
· Antena wire (3wire &6 terminal) properly welded and in contact with former
· Antena rod and panel GLD wire connection should be tightened with bolt.
· During normal operation GLD sensitivity should be 100% (to give safety to operator and coil) So as to trip at 60ma.leakage current.
· Due to moisture in new lining, GLD value shows high at that time we need to switch off the CT temparely till the GLD value reduces. (Close monitoring required when CT is not running)