Selectable Overcurrent and Undercurrent Monitoring
A selector switch configures the relay for either overcurrent or undercurrent sensing. Adjustable fault trip current and trip delay settings allow the response to match the monitored load. The startup sensing delay postpones fault monitoring for 3 seconds when input power is applied, and the red LED indicates a detected fault.
Features and Benefits
- Selectable sensing mode supports monitoring for excessive current or loss of current.
- Adjustable trip delay requires the fault condition to persist for the selected interval before the output relay energizes.
- Integrated current transformer provides through-hole conductor routing without a separate sensing transformer.
- Multiple conductor passes through the transformer increase sensitivity to lower currents.
- Encapsulated construction suits demanding industrial locations.
- SPDT contacts offer general-purpose, resistive, motor, and B300 pilot duty ratings.
- Surface mounting and 0.25-inch male quick-connect terminals support installation in control assemblies.
Operating Sequence and Automatic Reset
In overcurrent mode, the fault timing cycle begins when the monitored AC current rises above the selected fault trip level. If that condition continues for the adjusted trip delay, the output relay energizes. It remains energized until the current falls below the reset level.
In undercurrent mode, the fault timing cycle begins when the monitored current falls below the selected fault trip level. The output relay energizes after the trip delay if the condition persists, then de-energizes when the current rises above the reset level. Trip point hysteresis is −5% for overcurrent sensing and +5% for undercurrent sensing.
Current Transformer and Sensitivity
Route the monitored conductor through the integrated toroidal current transformer. Looping the conductor through the opening more than once increases the effective sensed current and improves sensitivity. Account for the number of conductor passes when selecting the trip setting and checking the 25 ampere-turn steady-current limit. The maximum inrush current is 150A for 10 seconds.
Applications
Use the CAH05A2AF in process control and equipment monitoring circuits that require an output when load current crosses a set threshold. Overcurrent monitoring can help detect locked-rotor conditions, while undercurrent monitoring can help identify load loss or an open heater or lamp circuit. Select the sensing mode, trip current, and time delay to match the equipment's normal operating current and startup behavior.
Installation and Selection Notes
- Mount the relay to a suitable surface using two #6 screws and allow space for conductor routing and terminal access.
- Connect a 120V AC supply within the specified +10%/−15% input voltage tolerance.
- Select overcurrent or undercurrent sensing and set the fault trip current and 0.15–7 second trip delay for the application.
- Consider the fixed 3-second startup sensing delay when assessing the required fault response.
- Match the switched load to the applicable AC, DC, horsepower, or pilot duty contact rating.
- Follow the CAH Series installation manual for wiring and setup details.
