JUMO 709062 TYA 202 - Three-Phase Power Controller Operating Manual - Manual (Page 84)

6 Special device functions
82 2012-12-31/00561073 [SCR power switch TYA202]
6.7 Current limiting
Function Current limiting prevents overcurrents in the load current circuit. It limits the
load current independently of the load resistance and the setpoint value to the
required current limit value by enlarging the phase control angle, if necessary.
Current limiting is unavoidable for heating elements with a high positive tem-
perature coefficient, such as Kanthal-Super, for example. Without current limit-
ing, the load current would accept inadmissibly high values when such heating
elements are in a cold state.
Factory setting Current limiting is not activated.
v Chapter 5.1.2 "Power controller"
6.8
α
start
Factory setting The phase angle of the first half-wave (
α
start) is not activated.
For transformer loads, the SCR power controllers operate in continuous burst
firing mode and in logic operation with phase control of the first half-wave.
The factory setting is an angle of 70 °el. (electrical). This value can be adjusted
at the configuration level or operator level within the range of 0 to 90 °el.
H
Current limiting is only possible for power controllers with load current
measurement (i.e. in the order details) subordinate control I,I
2
(code
010 in the order code), or P (code 001 in the order code) must be se-
lected.
The current limiting is implemented via phase angle control. It there-
fore only operates permanently in phase angle control mode.
If burst-firing mode is set, current limiting only operates in the soft
start phase if "With phase angle control" is set as the soft start type.
In three-phase economy circuit, only the current in the strand of the
master power controller is limited to the configured value. As a result
of the economy circuit, significantly greater load currents can flow in
the other two phases.
u
t
a a