Siemens SIRIUS Line Monitoring Relay, 3-Phase 3-Wire, 154–480V AC, 1 CO, Self-Powered, 17.5 mm - 7UG0712-1AA20

Product Description

The Siemens 7UG0712-1AA20 is a SIRIUS line monitoring relay designed to supervise 3-phase 3-wire AC electrical systems. It is a self-powered monitoring device that operates directly from the monitored supply, eliminating the need for a separate auxiliary control voltage. The relay has a 154–480 V AC line-to-line operating band, making it suitable for a wide range of three-phase industrial power systems.

The relay monitors important three-phase supply conditions including phase sequence reversal, phase missing and phase imbalance. Siemens specifies an instantaneous trip response for the monitored fault conditions, with a phase-failure trip below 154 V AC line-to-line and a fixed 30 V phase-imbalance threshold.

With 1 changeover (1 CO) relay output and a compact 17.5 mm module width, the 7UG0712-1AA20 is suitable for space-constrained control panels, motor control circuits, industrial automation systems and three-phase equipment where reliable power-supply supervision is required.

Key Features

• Brand: Siemens

• Product Family: SIRIUS 7UG

• Part Number: 7UG0712-1AA20

• Product Type: Line Monitoring Relay

• Network: 3-Phase 3-Wire

• Operating Voltage: 154–480 V AC (L-L)

• Rated System Supply Voltage: 415 V AC

• Control Supply: Built-in / Self-Powered

• Output: 1 CO

• Output Contact: 1 Changeover Contact

• Module Width: 17.5 mm

• Rated Frequency: 50/60 Hz

• Monitoring: Phase Sequence Reversal

• Monitoring: Phase Missing

• Monitoring: Phase Imbalance

• Phase Failure Trip: <154 V AC (L-L)

• Phase Imbalance Threshold: 30 V fixed

• Response Time: <400 ms

• Recovery Time: <400 ms

• Measuring Range: 54–480 V AC

• Operating Temperature: 0 to 50°C

• Degree of Protection: IP20

• Mounting: DIN Rail / Control Panel

• Standard: IEC 60947-5-1

Applications

The Siemens 7UG0712-1AA20 line monitoring relay is suitable for:

• Three-phase power supply monitoring

• Motor control panels

• Motor starter circuits

• MCC panels

• Industrial automation systems

• Machine control cabinets

• Three-phase motor applications

• Pump control systems

• Fan control systems

• Compressor systems

• Industrial machinery

• Factory automation

• Electrical distribution systems

• Phase sequence monitoring

• Phase failure monitoring

• Phase imbalance monitoring

• Equipment protection circuits

• Alarm and control systems

Benefits

• Reliable three-phase line monitoring

• Designed for 3-phase 3-wire systems

• Wide 154–480 V AC operating range

• Self-powered operation

• No separate auxiliary supply required

• Phase sequence reversal detection

• Phase missing detection

• Phase imbalance monitoring

• Fast fault response

• One changeover relay output

• Compact 17.5 mm module design

• Saves control-panel space

• Suitable for motor control applications

• Suitable for industrial automation

• Helps prevent operation under abnormal phase conditions

• Easy integration with contactors and control circuits

• Suitable for DIN-rail installation

• Genuine Siemens SIRIUS monitoring relay

Monitoring Functions

The 7UG0712-1AA20 supervises the three-phase supply and responds to several abnormal conditions:

• Phase Sequence Reversal: Detects incorrect phase rotation.

• Phase Missing: Detects loss of a phase in the monitored three-phase supply.

• Phase Failure: The specified phase-failure trip occurs below 154 V AC L-L.

• Phase Imbalance: Monitors phase imbalance using a fixed 30 V threshold.

The relay is self-powered, meaning its control supply is derived from the monitored three-phase network.

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Frequently Asked Questions

Q1. What is Siemens 7UG0712-1AA20?
The 7UG0712-1AA20 is a Siemens SIRIUS line monitoring relay designed for monitoring three-phase, three-wire AC electrical systems.

Q2. What voltage range does the relay monitor?
It has an operating band of 154–480 V AC line-to-line.

Q3. What is the rated system supply voltage?
The rated system supply voltage is 415 V AC for the 3-phase 3-wire application.

Q4. Does the 7UG0712-1AA20 require an auxiliary supply?
No. It is self-powered, with a built-in control supply derived from the monitored network.

Q5. How many output contacts does it have?
The relay provides 1 changeover contact (1 CO).

Q6. What faults can the relay monitor?
It monitors phase sequence reversal, phase missing/failure and phase imbalance.

Q7. What is the phase-failure trip threshold?
Siemens specifies a phase-failure trip when the line-to-line voltage falls below 154 V AC.

Q8. What is the phase-imbalance threshold?
The specified phase-imbalance threshold is 30 V fixed.

Q9. What is the response time?
The specified maximum response time is less than 400 ms, with a recovery time also below 400 ms.

Q10. What is the module width?
The relay has a compact 17.5 mm module width, making it suitable for space-saving control-panel installations.

Q11. Can it detect incorrect phase rotation?
Yes. Phase sequence reversal is one of its monitoring functions.

Q12. Is it suitable for motor control panels?
Yes. It can be integrated into motor control and automation circuits to supervise the incoming three-phase supply.

Q13. Is 7UG0712-1AA20 suitable for 3-phase 4-wire systems?
No. This specific model is specified for 3-phase 3-wire systems. Siemens lists the 7UG0814 and 7UG0818 models for 3-phase 3-wire and 3-phase 4-wire monitoring.

Q14. What is the main advantage of the self-powered design?
Because the relay derives its supply from the monitored network, no separate auxiliary control supply is required, simplifying panel wiring.

Q15. What standard is associated with the relay?
The Siemens operating instructions identify IEC 60947-5-1 for the 7UG0 monitoring relay range.

Q16. Where can Siemens 7UG0712-1AA20 be used?
Typical applications include MCC panels, motor starters, industrial automation, pumps, fans, compressors, machine control panels and three-phase electrical equipment.

Q17. Is this relay a circuit breaker?
No. It is a line monitoring relay. It detects abnormal three-phase supply conditions and switches its relay output so that an external control or protection circuit can respond.

Q18. Why use a phase monitoring relay with a motor?
Monitoring phase sequence, phase loss and imbalance can help prevent a motor from operating under abnormal supply conditions, supporting safer and more reliable motor-control operation.