D-Curve Protection for Circuits with High Inrush
The D trip curve accommodates brief startup current that can exceed a circuit's normal operating current. Its magnetic trip range is 10–20 times the rated current, corresponding to approximately 30–60A for this 3A model. This characteristic can help reduce nuisance tripping in appropriately selected control and transformer circuits with high initial inrush.
Thermo-magnetic operation provides two responses: the thermal element responds to sustained overloads, while the magnetic element responds to high fault current. The 30–60A magnetic trip range is separate from the breaker's 3A nominal rating and should be evaluated alongside the connected load's startup profile.
The three-pole configuration and DIN-rail mounting suit panel assemblies that require a compact protective device for three conductors. A contact-position indicator provides a visual reference during inspection and troubleshooting. The housing measures 108 mm long by 52.5 mm wide by 67 mm deep, allowing panel builders to plan mounting space and wiring access.
Key Features and Benefits
- 3A current rating: Supports circuits requiring a low nominal protective-device rating.
- Three-pole configuration: Provides a 3-pole option for compatible AC panel circuits.
- D trip curve: A 10–20 × rated-current magnetic range accommodates suitable loads with brief, high inrush.
- 10kA breaking capacity: Supports applications where the available fault current is within the breaker's interrupting rating.
- DIN-rail installation: Integrates into industrial control-panel layouts.
- Contact-position indicator: Provides a visible contact-status reference.
- UL 489 approval: Supports branch-circuit protection when applied within the device's ratings.
Industrial Applications
The UB10D3003A is an option for low-current AC control branches, small control-transformer primary circuits, and inductive equipment circuits that require three poles and D-curve protection. Its suitability depends on the circuit's operating current, startup demand, voltage, and fault-current conditions. The 3A rating and 480Y/277V AC voltage rating should guide selection for the specific panel or machine.
Selection and Installation Considerations
Match the breaker to the required pole count, conductor capacity, load current, and system voltage. Check the available fault current against the 10kA breaking capacity and coordinate the D trip curve with normal startup current and other protective devices. The calibration temperature is 40°C (104°F), and the operating temperature range is −25°C to 55°C (−13°F to 131°F).
The terminals accept 18–3 AWG conductors with a fastening torque of 2.5 N·m (22.2 lb-in). Installation should follow the equipment documentation and applicable electrical requirements. Where separate motor-overload protection is required, it must be provided in addition to the circuit breaker.
Circuit Breaker Selection Resource
Compare IMO circuit-breaker series, pole counts, current ratings, and trip curves to select a model for your control-panel application.
IMO Precision Controls Circuit Breaker Selection Guide
