23
80994B_MHW_GTF-Xtra_05-2016_ENG
3.9
o
vercurrent
fault
Protection
16
bit
Reset alarms SHORT_CIRCUIT_CUR-
RENT E FUSE_OPEN
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).
- 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).
83
Fr.n
Number of restarts in case of FUSE_OPEN
R/W
R/W
OFF= -
ON = Reset alarms SHORT_CIRCUIT_CURRENT e FUSE_OPEN
Conditions of use
- Breaking capacity: 5 KA - 480V
- Max. system inductance: 500 uH
DIFFERENCES AMONG SHORT CIRCUIT PROTECTION DEVICES
Characteristics
Fuses
Magnetothermics
Overcurrent Fault Protection
Opening technique
•
Metal melting
•
Contact withdrawal with
preloaded spring
•
Thermal effect
•
Magnetic effect
•
Mechanical release
•
Current threshold
•
Device shutdown
Arc quenching
•
Arc in air / sand
•
Quenching with silica
sand / spring effect
•
Mechanical separation of 2 contacts
•
Arc in air with quenching in chamber
•
No arc in air (current shuts down
in silica)
Opening energy
(I²t of opening)
Depending on model:
•
Low – medium – high
Depending on model:
•
Medium – high
•
Always very low
Opening time
Depending on model:
•
Low – medium – high
Depending on model:
•
Medium – high
•
Always very low (micro-seconds)
Reset
•
Replacement
•
Labour cost + fuse
change
•
Manual reset
•
Manual reset
•
Automatic reset (“FR.n” times)
•
Remote reset (via serial)
