Why Choose the ABB TR4/A Toroidal Transformer?
The ABB TR4/A is an openable-core toroidal transformer designed for residual-current and earth-leakage monitoring systems using compatible ABB monitoring relays. Its 110 mm internal diameter provides ample space for circuit conductors, while the split/openable construction allows installation around existing cables without requiring the conductors to be disconnected and passed through a closed core.
Designed for use with compatible ABB RD2, RD3 and ELR residual current relays, the TR4/A detects the current imbalance associated with earth leakage and provides the measurement signal required by the connected monitoring relay. Its openable design is particularly advantageous for retrofit installations, existing switchboards and applications where disconnecting power conductors would be difficult or disruptive.
The TR4/A combines a 110 mm aperture with robust construction, IP20 protection and flexible installation in any orientation. It is suitable for commercial and industrial distribution systems where dependable residual-current sensing and convenient installation around existing conductors are required.
Key Advantages
- Openable-core construction allows installation around existing conductors without threading cables through a closed toroid.
- 110 mm internal diameter accommodates multiple conductors and larger cable arrangements.
- Designed for residual-current and earth-leakage monitoring.
- Compatible with ABB RD2, RD3 and ELR residual current relays.
- 300 mA minimum measurable current.
- Can be installed in any mounting orientation.
- IP20 protection for installation within suitable electrical equipment and enclosures.
- Particularly useful for retrofit and existing-installation applications.
Key Features
- ABB TR series toroidal transformer.
- 110 mm internal aperture.
- Openable / split-core design.
- 300 mA minimum measurable current.
- Suitable for connection to compatible external residual-current monitoring relays.
- IP20 degree of protection.
- -10 to +70 °C operating temperature range.
- Flexible installation in any position.
- Designed for commercial and industrial earth-leakage monitoring systems.
- Convenient installation around conductors already connected in an electrical system.
Openable-Core Residual Current Monitoring
The ABB TR4/A operates by surrounding all live conductors of the monitored circuit. During normal operation, the vector sum of the currents passing through the toroid is effectively zero. If current leaks to earth, an imbalance develops and the TR4/A produces a corresponding measurement signal for the connected residual-current monitoring relay.
Unlike the closed-core TR4, the TR4/A can be opened and installed around conductors that are already connected. This makes it particularly valuable for retrofit projects and existing switchboards where removing or disconnecting large power cables would be impractical. The connected ABB monitoring relay provides the applicable sensitivity, timing, alarm and trip functions for the complete earth-leakage monitoring system.
Typical Applications
- Earth-leakage and residual-current monitoring systems.
- Retrofit residual-current monitoring installations.
- Existing commercial electrical distribution boards.
- Industrial switchboards and control panels.
- Machinery and automation electrical systems.
- Three-phase feeder and distribution circuits.
- Systems using compatible ABB RD2, RD3 or ELR residual current relays.
- Applications requiring a 110 mm openable-core toroidal transformer.
