O que significam A e H no relé de sobrecarga térmica Chint NR2-25?

The Meaning of A and H in Chint Thermal Overload Relay NR2-25

The A and H markings on Chint thermal overload relay NR2-25 are reset mode selection indicators, which are used to set the reset mode after the relay trips due to overload protection:

UM: Stands for Automatic reset. After tripping due to overload, the relay will automatically return to its initial state when it cools down to the set temperature, without manual intervention.

H: Stands for Hand reset. After tripping due to overload, the relay can only be reset by manually pressing the reset button, which prevents safety accidents caused by automatic restart of equipment before the fault is eliminated.

Reset Mode Switching Method

The reset mode of NR2-25 is switched via a blue knob:

1. Press the blue reset button with a screwdriver and rotate it clockwise.
2. Rotate A to the top position: Set to automatic reset mode.
3. Rotate H to the top position: Set to manual reset mode.

Application Scenario Recommendations

All thermal overload relays in Chint NR2 series are equipped with functions such as temperature compensation, trip indication, automatic/manual reset switching and shutdown, among which reset mode selection is one of the core operations.

Overview of Recommended Thermal Overload Relay Brands Besides Chint

In addition to Chint, mainstream thermal overload relay brands on the market are divided into two categories: international first-tier brands (advanced technology, stable quality) and high-quality domestic brands (econômico, suitable for local needs). Each has its own characteristics and applicable scenarios, with detailed recommendations as follows:

1. International First-tier Brands
2. Schneider Elétrica

Série Representativa: Série LRD (tipo econômico), LRN series (tipo padrão), LR9 series (heavy-duty type)

Principais vantagens:

High trip accuracy and wide temperature compensation range (-25℃~+60℃), suitable for complex working conditions.

Equipped with complete functions such as phase failure protection, manual/automatic reset switching, and trip indication.

Perfectly compatible with LC1 series contactors, featuring convenient installation and low maintenance cost.

Cenários Aplicáveis: Large-scale factory automation, edifícios altos, protection of critical equipment (por exemplo, elevadores, bombas de água)

2. Siemens

Série Representativa: 3RV series (motor protection combination), 3UA series (traditional thermal overload relays)

Principais vantagens:

German craftsmanship, with mechanical service life up to 10 million operations and electrical service life up to 5 milhões de operações, achieving excellent stability.

Forte capacidade anti-interferência, suitable for high electromagnetic interference environments (por exemplo, near frequency converters).

Supports thermal memory function to record overload history for easy fault analysis.

Cenários Aplicáveis: Precision manufacturing industry, indústria química, metallurgy and other harsh industrial environments

3. ABB

Série Representativa: TA series (tipo padrão), Tmax series (integrated with circuit breakers)

Principais vantagens:

Wide setting current range (0.1A~1000A), covering applications from micro motors to large-scale equipment.

Unique bimetallic strip design for fast and accurate overload response.

Can be seamlessly combined with ABB contactors and circuit breakers to form a complete protection solution.

Cenários Aplicáveis: Sistemas de energia, heavy machinery, novos equipamentos de energia (por exemplo, energia eólica, fotovoltaico)

4. Eaton (including Moeller)

Série Representativa: Série ZB (tipo padrão), ZM series (tipo modular)

Principais vantagens:

Inherited German technology, with excellent anti-vibration performance (compatível com IEC 60068-2-6 padrão).

Equipped with tamper-proof protection to prevent safety hazards caused by incorrect setting.

Modular design supporting DIN rail mounting, economizando espaço no gabinete de controle.

Cenários Aplicáveis: Automobile manufacturing, port machinery, mining equipment and other high-vibration environments

5. Omron

Série Representativa: TH-N series, TH-K series

Principais vantagens:

Japanese precision manufacturing, with trip error <±5% and high protection accuracy.

Tamanho compacto, suitable for high-density installation in control cabinets.

Forms a complete control link with Omron PLCs, relays and other products, featuring good compatibility.

Cenários Aplicáveis: Electronic manufacturing, food packaging, small-scale automation equipment

1. High-quality Domestic Brands (Cost-effective Options)
2. Delixi Eletrônica

Série Representativa: JR36 series (traditional type), JRS3 series (new type)

Principais vantagens:

Price is only 1/3~1/2 of international brands, with performance close to international standards.

Adapted to the characteristics of domestic power grids, with strong resistance to voltage fluctuations.

Provides 3-year warranty with a sound after-sales service network and fast response.

Cenários Aplicáveis: Production lines of small and medium-sized enterprises, civil buildings, general industrial equipment

2. People Electric Appliance

Série Representativa: JR20 series (heavy-duty type), JRS5 series (tipo econômico)

Principais vantagens:

Strong short-circuit withstand capability, able to withstand 6 times the rated current impact.

Adopts silver alloy contacts with good conductivity and arc oxidation resistance.

Supports manual/automatic reset switching for convenient operation.

Cenários Aplicáveis: Construction sites, maquinaria agrícola, general equipment protection

III. Brand Comparison and Selection Recommendations

Principais pontos de seleção

1. Parâmetros do motor correspondentes: Ensure the setting current range of the thermal overload relay covers the rated current of the motor (usually 1.05~1.1 times the rated current).
2. Function Requirements: Select products with functions such as phase failure protection, thermal memory, manual/automatic reset according to application scenarios.
3. Compatibilidade de instalação: Match the installation dimensions and electrical interfaces of contactors and circuit breakers.
4. Adaptabilidade Ambiental: Select products with corresponding protection levels for high-temperature, high-humidity and vibration environments.