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7. Overvoltage protection (Crowbar)
After mounting of a thyristor BTY91/400R, the connected circuit can be protected against
too high voltages with the overvol tage protection.
This thyristor must be mounted insulated in the relevant mounting hole (see fig. 1 to 4 for
PE 1228; PE 1229-PE1233; PE 1230-PE 1234 and PE 1231-PE 1235 respectively).
The mounting material required (mica sheet, grommet and cable tag) is deliverable at
service department under code number 5322 255 40101. Connect the anode of the thyristor
to the "+" output terminal and the cathode to the "-" terminal (in РЕ 1228, РЕ 1229,
PE 1230, PE 1233 and PE 1234, connection wires are already available).
Connect the gate to point 17 of U] see fig. 5.
The trip voltage (V;) is adjustable between 10 and 40 V.
Adjustment is effected by means of a resistor (R62) which must be mounted on printed wiring
board U1.
VS
For the value of R62 applies:
5
ко
Where М, is the required trip voltage in volts at which the overvoltage protection is actuated.
As soon as the cause of the overvoltage has been eliminated, Vu can be reset by short-lived
interrupting the mains voltage.
8. Series connection
Series-connection of two or more units is permissible.
To prevent the polarity at the output terminals from reversing, a diode BYX42-300R, should
be connected in reverse direction across the output.
See detailed diagram fig. 13.
The diode can simply be mounted in the appropriate mounting hole of rectifier U3 in the
PE 1228, PE 1229 or PE 1233 see fig. 1 and 2, and rectifier U4 in the PE 1230, PE 1231,
PE 1234 or PE 1235 see fig. 3 and 4.
Connect the cathode to the "+" output terminal.
Two resistors R. should be series-connected across the total output voltage as shown in fig. 13
Rae 808
22
710
Unit 1 (master) controls via this voltage divider unit Il (slave) at terminal 3.
lu and lu, of unit 1 should be set to values which are approximately 2 % lower than those
of unit |.
The same system can also be applied for three or more units.
9. Parallel connection
Several units may be connected in parallel.
For this purpose a diode BYX42-300 should be connected in reverse direction across
transistor TS71. See detailed diagram fig. 14.
This diode can be fitted in the appropriate mounting hole of rectifier U2 in the PE 1228,
PE 1229 or PE 1233 see fig. 1 and 2 and rectifier U4 in the PE 1230, PE 1231, PE 1234
or PE 1235. See fig. 3 and 4.
Connect the anode to the "+" ouiput terminal.
If the units are connected in parallel, a thyristor SCR, must be applied, in case the
overvoltage protection is used.
The thyristor SCR¿_ must be calculated for the total short-circuit current of the parallel
connected units.
|
Mount thyristor SCR, on a separate heat sink and connect to the common output (anode to
the "+" output terminal and the cathode to the "-" output terminal);
Connect the gate to terminal 4 of one of the units. In the same unit, mount resistor R62
for adjusting of the overvoltage protection. See also point 7 of this chapter.
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