Motor-Side Connection Of The Holding Brake; Protective Circuitry For The Brake - Siemens 1FT7 Configuration Manual

5.3.3

Motor-side connection of the holding brake

The brake connecting cable is included in the power cable. The insulation between the
power and brake connections is dimensioned for increased insulation to comply with
VDE 600 V / 1000 V UL. The relay K1, located between the coil and contact, must also have
increased insulation in order to protect the internal logic voltage (PELV=Protective Extra Low
Voltage). The PELV supply may not be used to supply the holding brake (refer to Fig.
"Recommended circuit for the external power supply with protective circuit").
The minimum voltage of 24 VDC -10% must be available at the connector on the motor side
in order to guarantee that the brake reliably opens. If the maximum voltage of 24 VDC +10%
is exceeded, then the brake could re-close. The voltage drop along the brake feeder cable
must be taken into consideration.
The voltage drop ∆U for copper cables can be approximately calculated as follows:
∆U [V] = 0.042 ∙ (l/q) ∙ I
5.3.4

Protective circuitry for the brake

CAUTION
In order to avoid overvoltages when shutting down and the possible negative impact on the
plant or system environment, a protective circuit must be integrated into the feeder cable
(refer to Fig. "Recommended circuit for the external power supply with protective circuit").
Figure 5-2
1FT7 Synchronous Motors
Configuration Manual, (PFT7S) 01/2009, 6SN1197-0AD13-0BP2
Brake
Recommended circuit for the external power supply with protective circuit
l = Cable length [m]
q = Brake core cross section [mm
I = DC current of brake [A]
Brake
Motor components
5.3 Holding brake (option)
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