Operation Of Calibration System; Load Resistors; Magnetic Switches; Types Of Load - Fronius 4000 R Bedienungsanleitung

OPERATION OF CALIBRATION SYSTEM

LOAD RESISTORS

Four water-cooled load resistors (20, 40, 80 and 160mΩ) connected in
series inside the calibration unit allow selection of any value within the
range of 0 and 300mΩ in 20mΩ steps.
MS2* MS3*
20mΩ 40mΩ
MS1**
Power source
*..... Switch set to 1
**.... Switch set to 0
Fig.8 Connection diagram of load resistors

MAGNETIC SWITCHES

Switching the magnetic switch under load will produce a momentary
spark gap! To protect the contacts never switch the calibration system
under load, i.e. set the current to a minimum or switch off/disconnect
power source.
In case switching under load is inevitable make sure the current does not
exceed 100A!

TYPES OF LOAD

Short circuit
There is a short circuit when MS1 - MS5 are closed (Load resistor switch
set to "0" and Load resistor switch On/Off
mode, it is not absolutely required that the cooling unit mains switch
is set to On.
Load / resistor
Open the respective switches MS2 - MS5 to select the required resistors
(Load resistor switch set to "1") and close MS1 (Load resistor switch
On/Off set to "1"). In case various resistors are selected, the
respective values are added as the resistors are connected in series. The
cooling circuit has to be switched on as otherwise MS1 will not close.
Load limits
Acc. to the type plate the load limit is appr. 2,6 kW with a 100 % duty cycle
and 3,5 kW with a 60 % duty cycle. A 60 % duty cycle means that within
a cycle of 10 minutes a 6 minute load period is followed by a 4 minute
cool-down.
Caution! The current at the current inputs must never exceed
500A. Observe the load diagram to preclude a surcharge of the
load resistors! Make sure that the welding unit is switched off
when being connected!
MS4* MS5*
80mΩ 160mΩ
set to "1"). In short-circuit
9
t [min]
10
8
6
4
2
5 10
20mΩ 40mΩ
Fig.9 Load diagram

SAFETY DEVICES FOR LOAD RESISTORS

MS1 will open as soon as one of the safety devices mentioned below is
triggered (in any case the power source has to be switched off/
disconnected or the current be set to the minimum):
Temperature control
A thermal switch is mounted on each load resistor. As soon as the
temperature of the cooling water rises above 75° MS1 is opened
automatically; further the Excess temperature lamp
the temperature falls to a permissible value the Excess temperature lamp
goes out and MS is reclosed.
Water flow control
A flowmeter is fitted to the cooling unit which will open MS1 as soon as
there is no or insufficient water flow. Check water level and water
backflow.

MEASUREMENT OF OPEN-CIRCUIT VOLTAGE

Acc. to IEC 60974-1 (valid for all machine produced in or after 1990) the
open-circuit voltage of welding units has to be checked using a particular
circuit for peak value measurement. This measurement circuit is active
as soon as the voltage measurement switch
Turn the open-circuit voltage dial
ranging from 200Ω to 5,2kΩ . Keep changing the load unit the highest
voltage value is displayed on the voltage display
corresponds to the peak value. Prior to performing a new measurement
push the "peak reset" switch to discharge the capacity that is present
in the measurement circuit.
Do not hold the "peak reset" switch!
Note! The standard position of the voltage measurement switch
during a calibration process is "U
voltage display will show the mean value.
P [kW]
15 20
60mΩ 80mΩ 100-300mΩ
is illuminated. As
is set to Upeak.
to load the power source with a value
. This value then
". With the switch in this position the
eff