REOTRON MDW 700
Operating instructions
23
13.0 Installation of Thyristor Control Units
13.1 Fuses
The REOTRON MDW... series of thyristor controllers are fitted with semiconductor fuses, which protect
the power semiconductors (thyristors) from damage when there is a short-circuit on the output. These
fuses are selected for the permitted peak current of the semiconductors and are not provided for protec-
tion against overload or line faults! Fuses are provided only in the current-carrying circuits with thyristors.
Fuses for overload, line and earth fault protections should be fitted to the incoming power side.
13.2 Incoming breaker
An isolator must be connected in front of a thyristor-controller, mounted inside a control panel (VDE
0160/6.3.1) because of the leakage-current from a high-impedance thyristor and hence the current flow
through the protection circuit. This can be used to disconnect the unit from mains supply before a routine
shut-down.
Because all REOTRON thyristor-controllers have an enable input, it is possible to inhibit the input pulses,
and hence firing of the thyristors, until the main contactors have securely closed or before the contactors
open again when shutting down.
When enable inputs are used in this way, the contactors can be rated for current-free switching, in which
case AC1 would be suitable. If direct-on-line switching is used i.e. by switching the thyristor controller,
without using the enable, the rating of the contactors must be in accordance with AC3.
13.3 Output Breaker
A circuit-breaker on the output of the thyristor controller should be avoided, because it cannot operate
without a load. Current or voltage monitoring in the output of the thyristor controller must be used to con-
trol the circuit-breaker at the input side.
Current-free switching of the thyristor controllers’ output (e.g. load switching) is possible, however, by
using the enable input.
13.4 Installation and climatic Conditions
The mounting base should be free of vibration, if possible. Note that the temperature of the heat-sink
rises when a power controller is operating. The heat-sink must be mounted vertically to ensure efficient
cooling. The ambient temperature range allowed below the heat-sink is 0°...+45°C. The relative air hu-
midity is < 75% without dew. The clearance below the unit should be at least100mm and above at least
150mm. There must be a clearance of 50mm between units mounted next to each other. For altitudes
above 1000m the power must be derated by 0,5% per 100m additional height.
13.5 Signal cables
Set Points
If external voltage (0...10V) or current (0(4)...20mA) set-points are used; care should be taken to ensure
that all equipment is connected through equal-potential bonding. If the bonding is earthed, then this
should be at a single point, thus avoiding earthing loops and possible coupled interference.
Содержание REOTRON MDW 700
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