K3 Line contactor with auxiliary contacts R1 Braking resistor with temperature switch
S1 Key for switch on R2 PTC or KTY84 sensor e.g. of the motor
S2
Emergency stop circuit braker for switch off
DR1
Mains choke with temperature switch (optional)
H1 Tripping control HF1 HFlter
G1
Inverter with GTR7 evaluation (relay 30 V DC/ 1 A) and programmable input I1
The gure serves only as an example and must be adjusted according to the appli-
cation.
2.7.5.3 Braking resistor with over-heat protection without GTR7 monitoring
This circuit offers a direct protection with defective GTR7 (braking transistor). The braking re-
sistor overheats and opens the OH terminals with defective GTR7. The OH terminals open the
holding circuit of the input contactor, so that the input voltage is switched off in error case. An
error in inverter is released by opening the auxiliary contacts of K3. Regenerative operation is
also secured by the internal fault disconnection. The input must be programmed and inverted
to "external error". Automatic restarting after cooling of the braking resistor is prevented by the
self-holding circuit of K3.
If the PTC/KTY evaluation of the motor at terminals T1/T2 is not used, these termi-
nals can be used instead of the programmable input. The temperature input must
be operated in PTC mode.