The PETER Electronic VersiSafe is a safety standstill monitor that fundamentally rethinks how motor standstill is detected for safety-related applications. Unlike traditional methods that rely on external encoders or proximity sensors, the VersiSafe connects directly to motor terminals (L1, L2, L3) and measures the induced back EMF voltage generated by the freewheeling motor after it is disconnected from the supply. This "remanence voltage" diminishes predictably as the motor coasts to a stop. By continuously monitoring this voltage via two redundant measuring channels (L2-L1 and L3-L1), the VersiSafe reliably determines when the motor has reached a safe stationary condition. This sensorless approach eliminates the cost, complexity, and potential failure points associated with external sensing hardware, while also being independent of the motor's direction of rotation.

From a functional safety perspective, the VersiSafe is certified to the highest industry standards. It achieves Safety Integrity Level 3 (SIL 3) according to IEC/EN 61508, Performance Level e (PL e) with Safety Category 4 according to ISO 13849-1, and SIL CL 3 according to EN 62061. These certifications are backed by exceptionally strong reliability metrics, including a Mean Time to Dangerous Failure (MTTFd) of 93 years, a Diagnostic Coverage (DCavg) of 99.0%, and an extremely low Probability of Dangerous Failure per Hour (PFHD) of just 4.10E-10. The device achieves a Hardware Fault Tolerance (HFT) of 1 and a Safe Failure Fraction (SFF) of 99.7%. The core safety architecture relies on force-guided relays: three normally open (NO) safety contacts (23-24, 33-34, 43-44) and one normally closed (NC) auxiliary contact (11-12). The NC contact is mechanically linked to the NO contacts, ensuring that a welded NO contact prevents the NC contact from closing—a fault immediately detected by the internal diagnostic circuits.

The VersiSafe incorporates multiple layers of diagnostic coverage. A failure check is performed on power-up and continuously during operation. The device includes broken wire detection that monitors the measurement lines for continuity and DC offset; a simultaneity monitoring function that compares the two measurement channels and triggers a fault if they differ for more than 2.5 seconds; and a feedback circuit (EDM) on terminals X1-X2 that verifies external contactors are in their initial state before enabling safety outputs. When a fault is detected, the safety outputs are immediately disabled, and the red "ERR" LED flashes a specific code indicating the failure type. The response value Uan (threshold for standstill detection) is adjustable from 20mV to 400mV (special variants up to 4V), and the standstill time delay ts can be set from 0.2 to 6 seconds. These adjustments allow the VersiSafe to be precisely adapted to different motor characteristics and application requirements.

Installation and commissioning are straightforward. The 45mm wide housing mounts on standard DIN rail. The auxiliary voltage can be AC 230V, AC 400V, or DC 24V, with maximum consumption of 5VA or 3W. LED indicators on the front panel provide clear status information: "UH" (green) for auxiliary power, "OUT" (yellow/green) for standstill status, and "ERR" (red) for fault indication. The VersiSafe is designed for operation in ambient temperatures from -20°C to 50°C and carries an IP20 protection rating, requiring installation in a control cabinet with at least IP54 protection. Typical applications include releasing protective devices on machine tools, preventing unexpected start-up of hazardous machinery, and enabling safe access to rotating equipment. The VersiSafe is compatible with three-phase, single-phase, and DC motors that generate remanence voltage when freewheeling, and can be used with inverters provided they do not generate voltage at standstill. For motors with star-delta starters, proper wiring of the star contactor is essential to maintain a closed measurement circuit when the motor is switched off.

Technical Specifications