Modular | digital automatic backup power transfer switch with protection functions | for generators | for uninterrupted power supply | 4P | 100A | 120V/230V | DIN

Three-phase automatic transfer switch ATS is designed to automatically transfer a three-phase load between the main and backup power sources. The microcontroller-controlled device monitors phase voltage, current, phase sequence, three-phase voltage and current imbalance, and temperature. If unsuitable parameters of the main source are detected, the device can automatically transfer the load to another suitable power source.

The device supports AC 120V and AC 230V phase-voltage systems. Protection thresholds and operating parameters are configured in the controller menu. In a 230V phase-voltage system, the device can be used in a conventional approximately 400V three-phase system.

Operating principle

The ATS is used with two three-phase power sources – a main source and a backup source. The device monitors the parameters of the main source and, if a fault or unsuitable voltage is detected, can automatically transfer the load to the backup source after the configured delay.

Automatic and manual control

The device supports automatic and manual operating modes. In automatic mode, monitoring and transfer between the sources are handled by the controller. Manual mode allows the operator to control the transfer according to the requirements of the specific installation.

Power source priority selection

Parameter P-13 allows the power source priority operating mode to be selected. This makes it possible to define which source should be used as the main source or to select a mode in which automatic return to the priority source is disabled.

Overvoltage and undervoltage protection

Overcurrent protection

The overcurrent protection threshold can be adjusted from 1A to 100A. When the current exceeds the configured value, the device disconnects the circuit after the selected delay.

Repeated overcurrent trip lockout

Parameter P-11 allows the permitted number of repeated overcurrent protection trips to be configured from 1 to 20. Once the selected number is reached, the device may remain disconnected and require manual reset.

Three-phase voltage imbalance protection

The device monitors the difference between the phase voltages of the three-phase system. If the configured imbalance threshold is exceeded, protection is activated and, if another power source is suitable, the load can be transferred.

Three-phase current imbalance protection

Parameter P-17 can be used to activate three-phase current imbalance protection. The permitted current difference between phases is adjustable from 0.5A to 10A. If the configured threshold is exceeded, the device can disconnect the load.

Phase sequence monitoring

The device detects an incorrect phase sequence. In the fault table, a phase sequence error is displayed as L1 L3 L2. This function is particularly important for three-phase loads where the correct phase sequence is essential.

Temperature protection

The temperature protection threshold is adjustable from 50°C to 150°C. The default setting is 100°C. After the temperature decreases, protection is restored with approximately 10°C hysteresis.

Automatic retransfer

After a mains fault has been cleared and the parameters return within the permitted limits, the ATS can automatically transfer or return the load to the selected source. The recovery / transfer delay is adjustable from 1 to 999 seconds.

ON / OFF timer

The controller has an integrated programmable load ON and OFF timer.

Voltage and current calibration

Measurement readings can be corrected in the settings menu. Both voltage and current calibration ranges are ±9.9% in 0.1% increments.

Digital display

The integrated digital display is used to show operating parameters, settings and fault information. Measurement accuracy: Class 0.5.

Fault diagnostics

Programmable parameters

Technical specifications

Advantages

Disadvantages / limitations

Suitable for

• Switching between main and backup three-phase mains supplies
• Mains–mains backup power systems
• Mains–generator systems, provided generator control is implemented using a separate suitable control circuit
• Industrial electrical systems
• Commercial and technical premises
• Pumps, fans and other three-phase loads, provided their parameters comply with the device specifications
• Systems where phase sequence and imbalance monitoring are important

Not suitable for

• Loads above 100A
• Parallel operation of different power sources
• As a replacement for a UPS uninterruptible power supply
• As a replacement for an SPD or short-circuit circuit breaker

Practical application example

Frequently asked questions (FAQ)

Three-phase automatic transfer switch ATS – a microcontroller-controlled transfer and protection device for two three-phase power sources, supporting AC 120V and 230V phase-voltage systems. It provides adjustable overcurrent protection up to 100A, overvoltage and undervoltage monitoring, phase sequence monitoring, three-phase voltage and current imbalance protection, temperature protection, programmable transfer delays, priority power source selection, ON/OFF timer and fault diagnostics.