PRODUCTS
Current Monitors
Current Monitors for Motors, Pumps and Industrial Equipment
ATC Diversified Electronics offers a broad range of AC and DC current monitors designed to detect changes in electrical load and provide a relay response when current moves outside established operating limits. Available products include over-current, under-current, current-band, Go/No-Go, three-phase current-unbalance, multifunction current-monitoring relays, and current transformers.
Monitoring motor and equipment current can provide useful information about how a load is operating. Depending on the application, a change in current may indicate conditions such as an overloaded motor, stalled or jammed machinery, loss of mechanical load, broken belts or chains, pump operating changes, or other conditions that affect electrical demand.
ATC current monitors range from simple magnetically coupled devices that detect the presence of AC current to adjustable multifunction relays with over-current, under-current, and current-window monitoring. AC and DC models, automatic and manual reset options, DIN rail configurations, adjustable time delays, and external current transformer compatibility are available depending on the product family.
Why Choose ATC Current Monitoring Relays?
Over-Current Monitoring: Selected ATC relays detect when current rises above an adjustable threshold. Time-delay options on applicable models can help distinguish sustained over-current conditions from normal motor starting inrush.
Under-Current Monitoring: Under-current relays can identify when electrical demand falls below an expected operating level. Depending on the equipment, this may indicate loss of load, a broken belt or chain, pump operating changes, or another process condition.
Current-Window and Band Monitoring: Selected models monitor both upper and lower current limits, allowing a load to be supervised against a defined normal operating band.
Go/No-Go Current Detection: ATC Go/No-Go monitors provide a straightforward way to determine whether AC current is present above a defined trip point and provide a relay response when that operating state changes.
Three-Phase Current Monitoring: The CLB Series monitors three-phase equipment for current unbalance and over-current conditions, providing an additional layer of protection for motors and other three-phase loads.
AC and DC Monitoring Options: ATC offers dedicated AC and DC current-monitoring families, allowing the monitoring method to be matched to the electrical system and load.
External Current Transformer Support: Many ATC current monitors can use an external current transformer to extend the measurable current range for higher-current applications.
Monitor Motor and Equipment Load Through Current
Current monitoring provides a practical way to supervise whether equipment is drawing the amount of current expected during normal operation. An over-current condition can be associated with increased mechanical load, a stalled motor, a jammed conveyor, or another condition that increases electrical demand.
An under-current condition can indicate that a motor or machine is running with less load than expected. Depending on the application, this can help identify conditions such as broken belts, broken chains, loss of pump load, or other changes that reduce motor current.
Current monitoring should be applied with knowledge of the normal operating current, motor starting characteristics, expected load variation, and the electrical and mechanical behavior of the equipment.
AC, DC and Multifunction Current Monitoring
ATC offers dedicated current monitors for specific control strategies. The CBA Series AC Current Band Monitor independently monitors adjustable upper and lower current thresholds. The CMD Series can be configured for either AC over-current or under-current monitoring and includes adjustable operate and release delays.
For DC applications, the CDD Series Universal DC Current Monitor provides over-current or under-current monitoring with adjustable trip and timing settings. Additional CDO and CDU products provide dedicated DC monitoring options.
The CMU100USD combines over-current, under-current, and current-window monitoring in a slim DIN rail relay with universal supply voltage, automatic or manual reset, external CT capability, and UL 508 approval.
Find the Right Current Monitor
Selecting the right current monitoring relay depends on whether the circuit is AC or DC, expected normal current, over- or under-current thresholds, allowable starting inrush, required time delays, reset behavior, relay-output requirements, mounting method, and whether an external current transformer is required.
Explore the ATC current monitors above to compare Go/No-Go, over-current, under-current, current-band, three-phase, AC, DC, and multifunction configurations. ATC Diversified Electronics can also assist with matching current-monitoring functions to motors, pumps, conveyors, HVAC equipment, machinery, and industrial process applications.
Current Monitor FAQs
What is a current monitoring relay?
A current monitoring relay measures or detects electrical current in a circuit and changes the state of an output relay when current reaches a defined operating condition. Depending on the model, it may monitor for over-current, under-current, current within or outside a window, or simply the presence or absence of current.
What is an over-current monitor?
An over-current monitor provides a relay response when measured current rises above a selected trip point. Selected ATC models include adjustable delays so normal motor starting current can pass without immediately triggering the monitor.
What is an under-current monitor?
An under-current monitor responds when electrical current drops below a selected operating threshold. Depending on the application, low current can indicate loss of mechanical load, a broken belt or chain, pump operating changes, or other conditions that reduce equipment demand.
What is a current-window or current-band monitor?
A current-window monitor supervises both a lower and upper current limit. The load is considered within its normal operating range while current remains between those thresholds. ATC products such as the CBA Series and CMU100USD provide forms of upper- and lower-limit current monitoring.
What is a Go/No-Go current monitor?
A Go/No-Go current monitor determines whether AC current is above or below a defined trip point. This provides a simple indication that a monitored load is drawing current or that current has fallen below the expected level.
How does the ATC CMG Series monitor current?
The CMG Series is magnetically coupled to the monitored conductor by passing the conductor through the monitor's current transformer. No physical electrical connection to the monitored AC line is required, and the CMG Series does not require a separate supply voltage.
Can the trip point of the CMG Series be changed by looping the conductor through the sensor?
Yes. Increasing the number of conductor turns through the CMG current transformer lowers the effective current trip point. For example, doubling the number of turns effectively halves the trip-current value specified for one turn.
What does the CBA Series AC Current Band Monitor do?
The CBA Series monitors both under-current and over-current conditions. Its upper and lower current trip points are independently adjustable, and separate relay outputs respond when current remains above or below the selected limits.
What does the CLB Series monitor?
The CLB Series is designed for three-phase equipment and monitors current unbalance and over-current conditions. It includes an inrush delay to prevent normal high starting current from immediately triggering the over-current function and supports automatic or manual reset.
What does the CMU100USD current monitoring relay do?
The CMU100USD is a DIN rail multifunction AC current monitoring relay that supports over-current, under-current, and current-window monitoring. It also provides universal supply voltage, automatic or manual reset, external current transformer capability, and a slim DIN rail housing.
Does ATC offer DC current monitors?
Yes. ATC offers several DC monitoring families, including the CDD Universal DC Current Monitor, CDO DC Over Current Monitor, and CDU DC Current Monitor Relays. Available functions include over-current and under-current supervision.
What is an adjustable current-monitoring delay used for?
A time delay prevents a current monitor from responding to every brief current change. In over-current applications, a delay can allow normal motor starting inrush to pass. In under-current applications, a release delay can prevent temporary load reductions from producing nuisance relay operation.
Can ATC current monitors measure higher currents with an external current transformer?
Yes. Many ATC current monitors can be connected with an external current transformer to extend the monitoring range beyond the current that the relay can measure directly.
What problems can motor current monitoring help identify?
Depending on the machine and application, changes in current can help identify conditions such as overload, motor or conveyor jams, broken belts or chains, loss of mechanical load, changing pump conditions, dull cutting tools, and other process changes that affect electrical demand.
Does a current monitor replace a motor overload relay?
Not necessarily. A current monitoring relay provides a control response based on selected current thresholds, while a motor overload device performs a specific motor-protection function. The appropriate devices depend on the motor, application, applicable requirements, and overall protection strategy.
How do I choose the right current monitor?
Start with whether the circuit is AC or DC and the normal operating current of the load. Then determine whether over-current, under-current, current-window, Go/No-Go, or three-phase monitoring is required. Also consider starting inrush, timing delays, reset behavior, relay outputs, supply voltage, mounting style, and whether an external current transformer is needed.