ABB XO08R2

Description

Product Overview

The ABB XO08R2 is a modular, configurable Electronic Overload Relay designed for motor protection and control, typically from ABB’s ES / ESH / ESN series or similar product lines. This device serves as a critical component in motor starter combinations, providing reliable protection for three-phase AC induction motors against overloads, phase loss, and phase imbalance. The primary function of the ABB XO08R2 is to continuously monitor the motor current via built-in current transformers, and to trip and open the control circuit if the current exceeds a preset threshold for a duration determined by its time-current characteristic curve. For detailed technical data, adjustment guides, and compatibility information, please refer to the official product resource: ABB XO08R2. This overload relay is a key element in ensuring motor longevity and preventing damage due to excessive thermal stress, forming an essential part of a motor starter assembly alongside a contactor.

Product Parameters and Specifications

• Function: Electronic Overload Relay for Motor Protection.
• Motor Current Range: The “08” in the model typically indicates a specific current setting range, often around 0.10 – 8.0 A or similar, suitable for smaller motors. The exact range is defined in the datasheet.
• Setting: Features a rotary dial or digital setting to adjust the trip current (I_e) within its specified range to match the motor’s full load current (FLC).
• Protection Functions:
  • Overload Protection: Based on a thermal replica with an inverse-time trip characteristic (Class 10, 20, or 30).
  • Phase Loss / Imbalance Protection: Detects loss of one phase or significant unbalance between phases.
• Contacts: Includes:
  • Auxiliary Contacts: Typically one normally closed (NC, 95-96) contact that opens upon trip (for breaking the contactor coil circuit) and one normally open (NO, 97-98) contact that closes upon trip (for signaling an alarm).
• Reset Function: Offers manual reset (via a button) after a trip. Some variants may offer automatic reset, though manual is standard for safety.
• Ambient Temperature Compensation: Electronic designs like the XO08R2 often include compensation to ensure accurate protection regardless of the ambient temperature around the relay.
• Mounting: Designed to mount directly onto the corresponding ABB contactor (e.g., of the A-line series) via a snap-on mechanical and electrical connection, or on a DIN rail.
• Status Indication: Usually includes a trip indicator (often a red flag or LED).

Advantages and Key Features

The ABB XO08R2 provides significant advantages over traditional bimetallic overload relays. Its electronic design offers higher accuracy and repeatability in trip times, along with ambient temperature compensation, leading to better motor protection. The inclusion of built-in phase loss protection is a major safety feature that simple thermal relays may lack. The clear, adjustable current setting allows for precise matching to the motor’s nameplate FLC, optimizing protection. Its compact and modular design allows for easy assembly with a matched contactor, creating a space-saving and reliable motor starter combination. The ABB XO08R2 is designed for long-term reliability and stability, with no risk of calibration drift due to aging or mechanical wear that can affect bimetallic strips. The trip indicator provides immediate visual fault identification.

Application Cases in Industry

This overload relay is used in virtually every industry for protecting small to medium-sized three-phase motors. Common applications include:

• Pumps and Fans: In HVAC systems, water treatment plants, and industrial ventilation.
• Conveyors and Material Handling: For drives on packaging lines, assembly systems, and warehouse conveyors.
• Machine Tools: Protecting motors on drills, lathes, and saws.
• Compressors and Chillers: In industrial refrigeration and air conditioning.
• General Industrial Machinery: Anywhere a reliable, standalone motor starter is required.

Comparison with Competing Products

• vs. Bimetallic Thermal Overload Relays (e.g., ABB TA series): Bimetallic relays are simpler and lower cost but less accurate, subject to ambient temperature effects, and lack built-in phase loss protection. The electronic XO08R2 offers superior protection performance and features.
• vs. Motor Protection Circuit Breakers (MPCBs): MPCBs combine short-circuit and overload protection in one device. The XO08R2 is an overload relay only and must be used with a separate contactor and short-circuit protective device (fuse or circuit breaker). This offers more flexibility in combining components but requires more panel space.
• vs. Advanced Motor Protection Relays: More sophisticated devices offer ground fault, jam, undercurrent, and communication capabilities. The XO08R2 is a cost-effective solution for basic, reliable overload and phase loss protection where advanced features are not required.

Selection Suggestions and Precautions

• Selection Advice:
  1. Motor Full Load Current (FLC) Match: The most critical step. The motor’s nameplate FLC must fall within the adjustable range of the ABB XO08R2. Set the dial precisely to the FLC value.
  2. Contactor Compatibility: Ensure the overload relay is compatible with the specific ABB contactor you are using. Verify the mechanical and electrical interface.
  3. Trip Class Selection: Select the appropriate trip class (e.g., Class 10 for fast tripping on pumps, Class 20 or 30 for motors with high inertia starts). The XO08R2 variant must offer the required class.
  4. Short-Circuit Protection: Remember that the XO08R2 does not provide short-circuit protection. You must install fuses or a circuit breaker sized for short-circuit protection upstream of the contactor.
• Important Precautions:
  1. Correct Phase Connection: Connect the three phase wires through the current transformers of the XO08R2 in the correct order (L1, L2, L3) as per the diagram. Incorrect wiring can cause malfunction.
  2. Auxiliary Contact Wiring: The NC contact (95-96) must be wired in series with the contactor’s coil circuit to break power on a trip. The NO contact (97-98) can be used for a remote alarm indicator.
  3. Allow Cool-Down After Trip: After an overload trip, allow time for the motor and the relay’s thermal memory to cool down before attempting a manual reset. Immediate resetting can cause immediate re-trip or motor damage.
  4. Testing: After installation, test the functionality by simulating an overload (if possible) or by using the test button (if equipped) to ensure the relay trips and opens the control circuit correctly.

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