Download Weld334m

Technical Manual
3.3
General protective devices on power supply
General schematic of protective devices.
Protection A:
Voltage/current limit circuit placed on the power feeder primary
24VI
24VI/VE
0V
Input stage
Internal power
feeder
5
6
7
8
PS
Protection :
Self-reset
state type solid fuse
On the basis of the type of connection in use, the protections operate in the following way:
◊
Protection A: General overvoltage and overcurrent protective circuit .
This protective device trips in the following cases:
1. If, when switching on the device, the line voltage exceeds the hazard limit of rated ranges.
2. In all cases of internal short circuit, on the output of the pulse control or of 24V signal of
the servovalve.
3. In case of overcurrent, if 24VI for I/O points is used both in the direct connection mode
(see paragraph 3.2.2 figure a) and in the indirect one (see paragraph 3.2.2 figure b).
With this type of connection, the protective device A, which features a faster switching
time, prevails on the device B.
In order to reset the functional conditions, it is necessary to cut off power and remove the
cause of the short, then switch on the device again after about 30”.
If by activating it again, the device does not switch On (RUN led indicator of CPU Off), then
check that line voltage is correct and that it complies with the characteristics indicated (if not,
the control device will stay off due to the protection device).
If all these conditions are observed but the device does not switch On, the power feeder is
likely to be damaged. Replace it.
◊
Protection B: current limit circuit on the external 24V supply.
It intervenes in case of use of the external 24V supply for the I/O points (see paragraph 3.2.2
figure c).
Once the cause has been removed, the protection resets automatically.
Characteristics of current limitation as a function of temperature*.
Power feeder type F350-PSM
Temperature* (°C)
20°
Current (A)
40°
50°
60°
3.75 3.04 2.70 2.36
Power feeder type F370-PSM
Temperature* (°C)
Current (A)
20°
40°
50°
60°
2.5
2.03
1.8
1.58
* Characteristics refer to the operating temperature of the component itself.
17