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S700 Safety Card S1-2 Safe Brake Control Error

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My application has a 115VAC external holding brake connected to an external relay driven by the SBC+ and SBC- output from the S700 safety card. Because the brake isn't connected directly to the safetycard, I'm getting error "Output SBC+/- does not switch off."

The safety card error manual says a wiring fault is expected but the wiring is okay. I suspect that the safetycard monitors the SBC terminals for a 24V brake but it instead sees the 24V relay coil.

The amplifier has a configuration option in parameter MBRAKE=4 to ignore apparent brake or wiring faults for its brake output. Is there something similar for the safety card? If not, what are the conditions that must be satisfied to avoid this error?





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1. Safe Brake Control and Safe Brake Test work hand in hand. You have to setup and execute the Safe Brake Test within the allotted time or you will get a fault.
2. Part of the setup is to set drive parameter CSCNFG to 1 or 4 or 5. You can see the description in the S700 ASCII command reference (attached). I am thinking “1” is the correct setting.
3. SBC+ and SBC- have “low current” and “high current faults”. Could be your relay is too low of 24V current or your relay has a high inrush peak 24V current (a 10 ohm resistor would help with the inrush current problem)
4. If your cables are longer than 10 meter, it’s recommended you install a ferrite donut as a common mode choke. Würth Elektronik, No. 7427729 is recommended.
5. The safety card and the drive’s 24V common have to be connected together.

To get a better idea of your problem, I need to know the fault and subfault code from the safety card and from the drive. Safety card error coder PDF is attached.

Dan Wolke


#3 was the trick. I had connected SBC- to the DC return bus which provided a different return path from the relay. Connecting SBC- directly to the (-) relay coil terminal solved the issue.

In the end, we will likely just use the safety card for SS1 functionality and move the brake control to the drive terminals.

Much Appreciated,

dwern - Thu, 08/27/2020 - 12:56
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