Siemens 5SN6420-7CN MCB Dedicated to Motor Overload Protection 4P 20A
The Siemens 5SN6420-7CN MCB is a specialized 4-pole, 20-amp Miniature Circuit Breaker engineered for dedicated motor overload protection. It offers advanced thermal and magnetic tripping mechanisms, ensuring precise safeguarding against sustained overcurrents and short circuits. With a rated breaking capacity of 10 kA, this MCB provides robust protection for electric motors in demanding industrial environments. Its compact design and easy DIN rail mounting facilitate seamless integration into control panels and electrical systems.
Product Specifications
| Feature | Specification |
| :---------------------------- | :-------------------------------------------- |
| Product Type | Miniature Circuit Breaker (MCB) |
| Dedicated Function | Motor Overload Protection |
| Number of Poles | 4 |
| Rated Current (In) | 20 A |
| Rated Breaking Capacity (Icn) | 10 kA |
| Tripping Curve | Type D (suitable for motor starting currents) |
| Voltage Rating (Un) | 400V AC |
| Frequency | 50/60 Hz |
| Terminal Type | Screw Terminals |
| Mounting | DIN Rail (35mm) |
| Protection Degree | IP20 |
| Operating Temperature | -25°C to +45°C |
Core Features & Market Positioning
The Siemens 5SN6420-7CN distinguishes itself as a purpose-built solution for motor protection, moving beyond the capabilities of standard MCBs. Its Type D tripping curve is specifically calibrated to withstand the high inrush currents characteristic of motor startups, thereby preventing nuisance tripping while maintaining effective protection against sustained overloads and short circuits. This specialization positions it as a premium component for applications where motor reliability and operational continuity are paramount. The integration of Siemens' renowned quality and engineering ensures a high level of safety and performance, differentiating it from more generic circuit protection devices.
Key Application Scenarios
This Siemens 5SN6420-7CN MCB is ideally suited for safeguarding electric motors in a wide array of industrial sectors, including manufacturing, material handling, pumps, fans, and HVAC systems. Its 4-pole configuration offers comprehensive protection for three-phase motors, ensuring all phases are disconnected in case of a fault. It is an essential component in motor control centers (MCCs) and individual motor starter assemblies where precise overload sensing is critical to prevent premature motor failure due to thermal stress or sudden short circuits. The 20A rating makes it appropriate for medium-sized industrial motors.
Practical System Integration Guidance
Integrating the Siemens 5SN6420-7CN MCB into an electrical system is straightforward due to its standard DIN rail mounting and terminal design. Ensure the upstream power supply is de-energized before commencing installation. Connect the power source to the line-side terminals (typically marked L1, L2, L3, and N for the neutral pole) and the motor connections to the load-side terminals. Verify correct wiring polarity for three-phase connections. The MCB is designed for use with appropriate conductor sizes rated for 20A, ensuring secure and reliable connections. It's crucial to adhere to local electrical codes and standards during installation.
Operation and Risk Mitigation
The 5SN6420-7CN operates by monitoring motor current. If the current exceeds a safe threshold for a predetermined duration (thermal overload), the bimetallic strip within the MCB heats up and trips the mechanism, disconnecting power. In the event of a severe short circuit, the electromagnetic coil generates a strong magnetic field, causing an instantaneous trip. This dual-action protection significantly mitigates the risk of motor winding damage, insulation breakdown, and potential fire hazards. Regular visual inspection for signs of wear or damage and periodic testing, as per maintenance schedules, are recommended for optimal risk mitigation.
Scalability & Long-Term Value
As part of the broader Siemens industrial automation portfolio, the 5SN6420-7CN MCB offers excellent compatibility with other Siemens components and systems, such as contactors, relays, and control panels. This facilitates seamless integration and potential upgrades within existing or new installations. While MCBs themselves are primarily protective devices, their robust design and reliable performance contribute to the long-term operational value of the protected equipment by minimizing downtime and repair costs associated with motor failures. For advanced monitoring and diagnostics, consider pairing this MCB with intelligent motor protection relays or communication modules within a broader IIoT strategy.
Frequently Asked Questions
1. What is the primary function of the Siemens 5SN6420-7CN MCB?
The Siemens 5SN6420-7CN MCB is specifically designed to protect electric motors from overload conditions. It provides essential safeguarding against excessive current that can cause motor overheating and damage. This dedicated function ensures motor longevity and operational reliability.
2. Why is a "Type D" tripping curve important for motor protection?
A Type D curve allows for higher inrush currents during motor startup without tripping. Motors draw significantly more current momentarily when they start. This curve prevents nuisance tripping while still offering robust protection against sustained overloads and short circuits.
3. What are the key technical specifications of the 5SN6420-7CN?
This MCB is a 4-pole device with a 20A rated current. It features a 10kA breaking capacity and operates at 400V AC. Its Type D tripping characteristic is vital for motor applications.
4. Can this MCB be used for single-phase motors?
While it is a 4-pole device, it can be adapted for certain single-phase motor applications by wiring two poles in parallel for the phase and utilizing the other two poles for overload sensing, or more commonly, by using a 2-pole version if available and appropriate for the specific motor's control scheme. However, its primary design is for three-phase motors.
5. What is the rated breaking capacity and why does it matter?
The rated breaking capacity (Icn) of 10kA indicates the maximum fault current the MCB can interrupt safely. A higher breaking capacity is crucial in industrial settings where fault currents can be substantial, ensuring the MCB can safely clear a short circuit without catastrophic failure.
6. How does the 5SN6420-7CN differ from a standard MCB?
Standard MCBs offer general circuit protection. This model is specialized for motor protection, incorporating a Type D tripping curve optimized for motor starting characteristics. Its focus is on preventing thermal damage to motor windings.
7. What type of environments is this MCB suitable for?
The Siemens 5SN6420-7CN is suitable for industrial environments with operating temperatures between -25°C and +45°C. Its IP20 protection degree means it is protected against solid objects larger than 12.5mm but not against water.
8. What does "4P" mean in the product name?
"4P" signifies that the Miniature Circuit Breaker has four poles. For motor protection, this typically means it can simultaneously disconnect all three phases of a three-phase motor and also includes a neutral pole for complete circuit isolation.
9. What is the voltage rating of this MCB?
The voltage rating (Un) for the Siemens 5SN6420-7CN MCB is 400V AC. This is a standard voltage for many industrial power distribution systems, particularly for three-phase applications.
10. How do I install this MCB?
Installation involves mounting it on a standard 35mm DIN rail in an electrical enclosure. Ensure the power is off, connect the line-side terminals to the power source and load-side terminals to the motor. Use appropriate sized conductors.
