West Control Solutions KS 800 Operating Instructions - Manual (Page 16)

Multi-Temperature-Controller KS 800
The current transformer input is not a measurement input in the sense of a calibrated measuring
instrument. The software for display calculation is designed for a single-phase 1000:1 current trans-
former (30A = 30mA). When applying other values to this input, there will be an error (3-phase
transformers, wave-form factor due to rectification and internal resistance outside KS 800...). Never-
theless, applying other variables to this input, e.g. 3-phase transformer with subsequent rectification
and totalizing is possible. In this case, scaling is not correct any more.
Therefore, the KS 800 current input must be matched to the relevant conditions:
Allow the current to be monitored of one heating loop to flow through the transformer. The relevant
controller measurement value is in a fixed ratio to the current, as long as the linearity limits are not
exceeded. E.g. the KS 800 display with 27A heating current is 19(A) (by additional external rectifi-
cation with a higher internal resistance). For monitoring a 10% current decrease, a limit of 17,1 (A)
must be adjusted.
However, the absolute measurement limits of transformer and KS 800 must not be exceeded:
1. The maximum current through the transformer(s). (When heating up the machine, all
heatings are switched on and the total of all heating currents flows through the
transformer(s). This current must be below the max. value permissible for this transformer,
otherwise, the transformer can be destroyed. For our transformers 9404 407 500x1, the
current limit is 100 A.
2. The maximum KS 800 input current must not exceed 100 mA (thermal limits).
3. Measurement is linear within 0 and approx. 35 mA.
When detecting an exceeded limit, this information is available at one of the alarm outputs or can
be read via the field bus.
Monitoring is done for exceeded min. and max. heating current limit.
Exceeded min. heating current limit: with the controller output switched off, an (adjustable)
heating current min. value is monitored, i.e. interruptions of the heating loop are detected.
Exceeded max. heating current limit: with the output switched off, monitoring is done for an
exceeded heating current limit of 3% of the heating current span (HC 100), which indicates leakage
currents.
The dyn. input resistance is approx. 170
Ω
Heating current monitoring is omitted, if a control loop is switched off.
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