Accelnet & Stepnet Plus Panels STO Manual 16-01338 Rev 00
Page 21 of 34 Copley Controls
8.0 Installation Using STO for Accelnet & Stepnet Plus Panels
8.1 STO Overview
This diagram gives detail on the physical cabling, shielding, and grounding of the wiring between the STO inputs
of the drive and the machine level safety circuits.
8.1.1 STO Power Requirements
The +24 Vdc power supply for the STO inputs must be SELV rated.
The +HV DC power supply for the drive power must be transformer-isolated from AC mains and voltage-
limited to +100 Vdc.
8.1.2 STO Wiring Requirements
Electrical connections to the STO inputs must meet the requirements for fault exclusions for short circuits
between conductors and short circuits between conductors and other conductive parts or earth or the
protective bonding conductor. These requirements are given in ISO 13849-2 and IEC 61800-5-2.
When driven from a single +24 Vdc power supply, the STO inputs must be connected in parallel as shown
above. Driving the STO inputs in series would require a higher voltage than the nominal +24 Vdc, and if one
of the STO inputs or its wiring were to fail as a short-circuit, it would apply the full DC power to a single input.
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