Undercurrent Protective Relays and Monitoring Relays
Description
Undercurrent protective relays and monitoring relays are devices designed to monitor electrical circuits and detect when the current falls below a predetermined threshold. When this occurs, the relay triggers an action, such as opening a circuit breaker, to protect the electrical system from potential damage due to undercurrent conditions.
Working Principle
Undercurrent relays operate by continuously measuring the current flowing through a circuit. They are set to trip when the current drops below a specific set point. This functionality is crucial because undercurrent conditions can indicate issues such as a fault in the power supply or a motor becoming unloaded. By detecting these conditions, undercurrent relays help prevent damage to equipment and ensure the reliability of the electrical system.
Applications
Undercurrent relays are commonly used in scenarios where maintaining a minimum current level is critical. For example, they are employed in motor protection to detect when a motor becomes unloaded, which can occur if a mechanical failure causes the motor to lose its load. They are also used in power supply systems to identify faults that result in reduced current flow, ensuring that corrective actions can be taken promptly to avoid equipment damage.
Advantages over other Protective Relays and Monitoring Relays
Undercurrent relays offer specific advantages in applications where detecting a drop in current is essential. Unlike overcurrent relays, which focus on excessive current conditions, undercurrent relays provide protection against scenarios where insufficient current can lead to equipment malfunction or damage. This makes them particularly valuable in applications involving motors and power supplies, where maintaining a minimum current is crucial for operational stability.
Limitations
One limitation of undercurrent relays is that they are not suitable for detecting overcurrent conditions, which require a different type of relay. Additionally, undercurrent relays may not be effective in systems where current fluctuations are common and do not necessarily indicate a fault, as this could lead to unnecessary tripping and interruptions.
Considerations
When selecting and implementing undercurrent relays, several factors should be considered. Initial costs can vary depending on the complexity and features of the relay. Operating expenses are generally low, but regular maintenance is necessary to ensure accuracy and reliability. Durability is an important consideration, as relays must withstand environmental conditions and electrical stresses. Accuracy in setting the trip point is crucial to avoid false tripping or failure to detect genuine undercurrent conditions. Replacement and maintenance costs should also be factored into the overall cost of ownership, as these can impact the long-term economic viability of using undercurrent relays in a given application.
from RS Components, Ltd.
Multifunction, Combined Current Relay [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 10
from RS Components, Ltd.
Monitoring relay 17.5mm 1 x SPDT [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 0.0200 to 0.5000
from RS Components, Ltd.
Monitoring relay 17.5mm 1 x SPDT [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 1 to 5
from RS Components, Ltd.
Monitoring relay 17.5mm 1 x SPDT 24V [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 1 to 5
from RS Components, Ltd.
Monitoring relay 17.5mm 24 V AC/DC [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 1 to 5
from RS Components, Ltd.
Monitoring relay 17.5mm 1 x SPDT [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 100 to 200
from RS Components, Ltd.
Monitoring relay 17.5mm 1 x SPDT [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 100 to 200
from RS Components, Ltd.
Monitoring relay 17.5mm [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 0.0200 to 0.5000
from RS Components, Ltd.
Monitoring relay 17.5mm [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 0.0200 to 0.5000
from RS Components, Ltd.
Monitoring relay 17.5mm [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 1 to 5
from RS Components, Ltd.
100A AC/DC CurrentMonitor built-in trans [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Frequency Sensing Range: 16.6
- Current Sensing Range: 100
- Approvals: RoHS
from RS Components, Ltd.
10A CurrentMonitor 1 Phase Multi 24-240V [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Frequency Sensing Range: 16.6
- Current Sensing Range: 10
- Approvals: RoHS
from RS Components, Ltd.
CURRENT CONTROL RELAY [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 1
from RS Components, Ltd.
CURRENT CONTROL RELAY [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 15
from RS Components, Ltd.
CURRENT CONTROL RELAY [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 15
from RS Components, Ltd.
Over or under current relay 0.5-15 A [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Approvals: RoHS
- Current Sensing Range: 15
from Littelfuse, Inc.
The 777-575-HRG-P2 three-phase current and voltage monitor provides motor protection with input voltage from 500 –600 V ac and motor full load ampere range of 2 –20 A (looped conductors required); 20 –90 A direct. [See More]
- Current Sensitive Relay: Undercurrent
from Macromatic Industrial Controls, Inc.
The CM Series is used to detect either an overcurrent or undercurrent condition. The pick-up current setting is user-adjustable within one of three ranges as shown in the Product Selection Table below. An external current transformer can be used to extend the range beyond 10 amperes. Choose between... [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Current Sensing Range: 0.1000 to 1
- Protective Functions: Time Delay
- Supply Voltage Range: 24
from Time Mark Corporation
The Model 1732 AC Current Monitor is a single set-point current monitor. It can be used to detect either over current or under current, depending on whether the trip point is set above or below the input current. Dual LED indicators on the front or top of the unit give a clear visual reference for a... [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Frequency Sensing Range: 50 to 400
- Current Sensing Range: 25 to 150
- Features: Visual Indicator
from Perfect Switch, LLC
Programmable Autonomous Relays have an integrated factory programmable microcontroller with options like timing features, delays, voltage sensing turn-on or turn-off, and logic feedback for easy system integration. Commonly used as a traditional Low Voltage Disconnect, the POWER-GATE Autonomous... [See More]
- Voltage Sensitive Relay: Overvoltage Protection; Undervoltage
- Protective Functions: Time Delay
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Features: Programmable Time Delay; Sealed Relay; Visual Indicator; Programmable
from Solcon Solutions LLC
Medium Voltage Control supply voltage:110V - 230V - 110-230V AC/DC Separate AUX19-60 VDC The MPS-3000 delivers a complete motor protection and control package. Monitoring 3-phase currents and voltage together with 10 RTD/Thermistor temperature inputs makes it an ideal solution for Medium and large... [See More]
- Voltage Sensitive Relay: Overvoltage Protection; Undervoltage
- Current Sensitive Relay: Over-Current Protection; Undercurrent
- Power (Phase) Sensing: Phase Failure (Loss); Sequence
- Supply Voltage Range: 110 to 230
from Littelfuse, Inc.
The 777-575-LR-P2 three-phase current and voltage monitor provides motor protection with input voltage from 500 –600 V ac and motor full load ampere range of 1 –9 A (direct); 10 –800 A (external CTs required). [See More]
- Current Sensitive Relay: Undercurrent
from Macromatic Industrial Controls, Inc.
The CU Series is used to detect an undercurrent condition. The drop-out current setting is user-adjustable within one of three ranges as shown in the Product Selection Table below. An external current transformer can be used to extend the range beyond 10 amperes. The pick-up current setting is fixed... [See More]
- Current Sensitive Relay: Undercurrent
- Current Sensing Range: 0.1000 to 1
- Protective Functions: Time Delay
- Supply Voltage Range: 24
from Time Mark Corporation
The Model 279 DC Current Monitor is a single set-point DC current monitor. It can sense either 1-10 Amps DC (24VAC or 120VAC) or 0.1-1 Amps DC (120VAC). The units have an input frequency of 50/60 Hz. The standard version, the 279B, has a screwdriver adjustable trip and hysteresis setting on top of... [See More]
- Current Sensitive Relay: Undercurrent
- Frequency Sensing Range: 50 to 60
- Current Sensing Range: 1 to 10
- Supply Voltage Range: 120
from Littelfuse, Inc.
The 777-575-P2 three-phase current and voltage monitor provides motor protection with input voltage from 500 –600 V ac and motor full load ampere range as follows: 2 –20 A (looped conductors required); 20 –90 A (direct); 90 –800 A (external CTs required). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 777-FT three-phase current and voltage monitor provides motor protection with input voltage from 200 –480 V ac and motor full load ampere range as follows: 2 –25 A: 3-phase (looped conductors required); 25 –90 A: 3-phase (direct); 80 –800 A: 3-phase (external CTs). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 777-HRG-P2 three-phase current and voltage monitor provides motor protection with input voltage from 200 –480 V ac and motor full load ampere range of 2 –20 A (looped conductors required); 20 –90 A direct. [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 777-HVR-LR-P2 three-phase current and voltage monitor provides motor protection with input voltage from 340 –480 V ac and motor full load ampere range of 1 –9 A (direct); 10 –800 A (external CTs required). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 777-HVR-P2 three-phase current and voltage monitor provides motor protection with input voltage from 340 –480 V ac and full load ampere range as follows: 2 –20 A (looped conductors required); 20 –90 A (direct); 90 –800 A (external CTs required). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 777-LR-P2 three-phase current and voltage monitor provides motor protection with input voltage from 200 –480 V ac and motor full load ampere range of 1 –9 A (direct); 10 –800 A (external CTs required). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 777-LR-TS three-phase current and voltage monitor provides motor protection with input voltage from 200 –480 V ac and motor full load ampere range as follows: 1 –4.5 A: 3-phase (looped conductors required); 2 –9 A: 3-phase (direct). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 777-MV-P2 three-phase current and voltage monitor provides motor protection with input voltage from 100 –240 V ac and motor full load ampere range of 10 –800 A (external CTs required). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 777-TS three-phase current and voltage monitor provides motor protection with input voltage from 200 –480 V ac and motor full load ampere range as follows: 2 –25 A: 3-phase (looped conductors required); 25 –90 A: 3-phase (direct); 80 –800 A: 3-phase (external CTs). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
777-LR-KW/HP-P2 three-phase current and voltage monitor provides protection with input voltage from 200 –480 V ac and motor full load ampere range as follows: 1 –2 A (looped conductors required); 2.1 –9.0 A direct; 10 –800 A (external CTs required). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 777-HVR-SP single-phase relay provides motor protection with input voltage from 340 –480 V ac and motor full load ampere range as follows: 2 –25 A (looped conductors required); 26 –90 A (direct); 80 –800 A (external CTs required). [See More]
- Current Sensitive Relay: Undercurrent
from Littelfuse, Inc.
The 77C-LR single-phase relay provides motor protection with input voltage from 100 –240 V ac and motor full load ampere range as follows: 1.0 –2.5 A (looped conductors required); 2.0 –9.0 A (direct). [See More]
- Current Sensitive Relay: Over-Current Protection; Undercurrent