gefran GTF-Xtra Installation And Operation Manual page 23

3.9 o
vercurrent fault Protection
This function eliminates the need for an external extra-rapid fuse to protect the device. The SHORT_CIRCUIT_
CURRENT alarm trips when the peak current on the load exceeds maximum permitted value (corresponding to twice
the rating ) during the softstart ramp or at first power-on (with softstart ramp disabled).
If configured (Fr.n parameter other than zero), the device restarts automatically in softstart for a maximum number
Fr.n of attempts, beyond which it remains deactivated while waiting for manual reset with front panel key BUT or with
the control via serial (bit 16).
83
Fr. n
16
Reset alarms SHORT_CIRCUIT_CUR-
bit
- DOES NOT replace any of the safeties on the system (such as magnetothermic switches, delay fuses, etc.).
- Protects the controller (and therefore also the load) by replacing the high-speed fuse needed to protect the control
SCRs against faults (without creating any additional cost to replace the fuse and reducing machine downtime).
-Has 2 function states:
√ Normal (On-Off control of load power)
√ Fuse-Open: GTF is open (a short occurred during normal operation).
Conditions of use
- Breaking capacity: 5 KA - 480V
- Max. system inductance: 500 uH
DIFFERENCES AMONG SHORT CIRCUIT PROTECTION DEVICES
Characteristics
• Metal melting
Opening technique • Contact withdrawal with
preloaded spring
• Arc in air / sand
Arc quenching • Quenching with silica
sand / spring effect
Opening energy Depending on model:
(I²t of opening) • Low – medium – high
Depending on model:
Opening time
• Low – medium – high
• Replacement
Reset • Labour cost + fuse
change
80994B_MHW_GTF-Xtra_05-2016_ENG
R/W Number of restarts in case of FUSE_OPEN
RENT E FUSE_OPEN
Fuses
• Thermal effect
• Magnetic effect
• Mechanical release
• Mechanical separation of 2 contacts
• Arc in air with quenching in chamber
Depending on model:
• Medium – high
Depending on model:
• Medium – high
• Manual reset
OFF= -
R/W
ON = Reset alarms SHORT_CIRCUIT_CURRENT e FUSE_OPEN
Magnetothermics Overcurrent Fault Protection
• Current threshold
• Device shutdown
• No arc in air (current shuts down
in silica)
• Always very low
• Always very low (micro-seconds)
• Manual reset
• Automatic reset ("FR.n" times)
• Remote reset (via serial)
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