Why Choose the ABB TR4 Toroidal Transformer?
The ABB TR4 is a closed-core toroidal transformer designed for use with ABB residual current monitoring and earth-leakage relay systems. With a generous 110 mm internal diameter, it allows the protected circuit conductors to pass through the transformer so that residual current can be measured without placing the monitoring device directly in the load circuit.
Designed for use with compatible ABB RD2, RD3 and ELR residual current relays, the TR4 detects the current imbalance associated with earth leakage and provides the measurement signal required by the connected monitoring relay. Its 500/1 transformation ratio and 100 mA minimum measurable current make it suitable for a wide range of commercial and industrial earth-fault monitoring applications.
The TR4 uses a robust closed-core construction and can be installed in any orientation. With a maximum insulating voltage of 1000 V AC, IP20 protection and a broad operating temperature range, it provides a dependable sensing component for ABB residual current monitoring systems.
Key Advantages
- 110 mm internal diameter accommodates multiple conductors and larger cable arrangements.
- Designed for accurate residual-current measurement in earth-leakage monitoring systems.
- Compatible with ABB RD2, RD3 and ELR residual current relays.
- 500/1 transformation ratio for integration with compatible ABB monitoring relays.
- 100 mA minimum measurable current.
- Closed-core construction provides a robust fixed installation.
- Can be installed in any mounting orientation.
- Suitable for commercial and industrial switchboards, control panels and electrical distribution systems.
Key Features
- ABB TR series toroidal transformer.
- 110 mm internal aperture.
- Closed, non-openable core.
- 500/1 transformation ratio.
- 100 mA minimum measurable current.
- 1000 V AC maximum insulating voltage.
- 2.5 kV dielectric test voltage at industrial frequency for 1 minute.
- 40 kA for 1 second maximum thermal overload.
- IP20 protection.
- Screw-terminal connections for conductors up to 2.5 mm².
Reliable Residual Current Measurement
The ABB TR4 operates by surrounding the live conductors of the monitored circuit. Under normal conditions, the vector sum of the currents passing through the toroid is effectively zero. If current leaks to earth, an imbalance develops and the TR4 provides a corresponding measurement signal to the connected residual-current monitoring relay.
With its 110 mm aperture, the TR4 is particularly useful where several conductors or larger cable sizes must pass through the same transformer. The toroid itself performs the residual-current measurement; the connected ABB RD or ELR relay provides the monitoring, adjustable sensitivity, timing and associated alarm or trip functionality appropriate to the system design.
Typical Applications
- Earth-leakage and residual-current monitoring systems.
- Commercial electrical distribution boards.
- Industrial switchboards and control panels.
- Machinery and automation electrical systems.
- Three-phase feeder and distribution circuits.
- Electrical installations using ABB RD2 or RD3 residual current relays.
- Systems using compatible ABB ELR residual current relays.
- Applications requiring a 110 mm closed-core toroidal transformer.
