NORD Drivesystems Adds New Safety Functions to NORDAC ON VFDs

Nord Drivesystems has expanded the motion-safety capabilities of its NORDAC ON and ON+ SK 300P variable frequency drives (VFDs) with Safe Maximum Speed (SMS), Safe Limited Speed (SLS), and Safe Speed Monitor (SSM) functions. The new capabilities enable drives to monitor and control motor speed locally while communicating fail-safe information through PROFIsafe or Functional Safety over EtherCAT (FSoE). By integrating safety functions directly into the VFD, manufacturers can reduce hardware complexity, support safety-critical tasks, and maintain controlled low-speed operation during setup and jam clearing.

NORDAC ON SK 300P is suitable for use with Nord IE3 asynchronous motors. Image used courtesy of Nord Drivesystems

Boosting Functional Safety

The NORDAC ON / ON+ SK 300P decentralized VFDs come with ingress protection ratings of IP55 and IP66, depending on the selected product variant, and a power rating of 0.5-5.0 hp (0.37–3.7 kW). These compact devices also have the capacity to accommodate a standard three-phase AC input voltage between 380 and 500 volts. Full plug-in-and-play functionality is provided to help remove complications associated with installation and deployment.

Integrated STO (safe torque off) immediately cuts off the energy supply that produces torque in the motor, and SS1 (safety stop 1) enables the machine in use to come to a controlled stop where the drive works by braking the motor electronically to come to a safe standstill.

The extended motion safety functions for the NORDAC ON VDFs include Safe Maximum Speed (SMS), Safe Limited Space (SLS), and Safe Speed Monitor (SSM). The SMS function limits motor speed to a threshold and initiates a safe-stop response if the limit is exceeded to maximize safety. The SSM provides a diagnostic reporting function. When the speed drops below a safe level, SSM sends a fail-safe message to a safety controller instead of initiating an internal trip. This keeps the machine running at a crawl while the controller performs external logic, such as opening safety guards or enabling safe-mode functions.

With 4x digital inputs and 2x digital outputs, customers can add fail-safe components, such as photoelectric sensors, emergency stop buttons, and/or safety door switches. With safety functions integrated directly into the NORDAC ON VFDs, customers do not need to worry about configuring an additional encoder.

An overview of the NORDAC modular system’s features and benefits. Video used courtesy of Nord Drivesystems

The NORDAC ON ON+ SK 300P VFDs are available for either wall or motor mounting, connect to a plug-in control module for parameter setting (NORDCON software tool or app), come with four parameter sets (which customers may switch online), V/f control, current vector control in open-loop and closed-loop mode, and Encoder Interface RS-485.

Control engineers can reduce hardware architecture complexity and costs by using the added safety functions mentioned above instead of an external encoder. By enabling the VFD to manage intricate motion monitoring locally and deliver fail-safe diagnostic information straight to the central controller over the industrial Ethernet backbone, built-in support for PROFIsafe and FSoE streamlines the safety loop.

By substituting monitored, controlled motion for conventional "hard stop" safety procedures, industrial businesses can optimize overall equipment effectiveness. SSM enables the system to switch to a safe "crawling"/go-slow mode, while SMS and SLS offer the active enforcement required to stop hazardous overspeed conditions. This helps mitigate downtime and reduce the mechanical strain of repeated restarts by allowing operators to complete tasks such as clearing jams or setting up the machine without an entire power cycle.