Permanent Magnet Solenoid
The Permanent Magnet Solenoid combines the characteristics of permanent magnets and electromagnets, offering stable and long-lasting magnetism.
The Permanent Magnet Solenoid combines the characteristics of permanent magnets and electromagnets, offering stable and long-lasting magnetism. It can maintain its magnetic force for an extended period without requiring continuous power, making it ideal for applications that need persistent holding force. Unlike traditional electromagnets, once energized, the permanent magnet can fix the magnetic field without the need for additional energy to sustain its magnetism, thus reducing energy consumption and extending the equipment's lifespan. Furthermore, it features a fast response time, enabling precise push-pull movements, making it suitable for applications where timing is critical.
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When selecting a solenoid, you must first determine its intended function, including whether it needs to push or pull, the stroke length, and the required force.
(1) Push Type vs. Pull Type
Push Type: When energized, the solenoid pushes the plunger outward. Suitable for mechanisms that require outward actuation.
Pull Type: When energized, the plunger is pulled inward. Commonly used in locking or latching applications.
Push-Pull Type: Capable of both pushing and pulling actions, ideal for systems requiring reversible motion.
Recommendation:
For locks, latches, or valves that require pulling action to unlock or activate, choose a pull type solenoid.
For ejecting components, bolts, or conveyor systems, use a push type solenoid.
(2) Stroke
The stroke refers to the maximum travel distance of the movable plunger. Typical stroke range is from 2mm to 30mm.
Recommendation:
Short stroke (2–5 mm): Ideal for high-frequency operations such as automation components and smart locks.
Long stroke (10 mm and above): Suitable for larger machines, such as mechanical clamps or electric door systems.
Note: Stroke length is inversely proportional to force — the longer the stroke, the lower the force.
(3) Push/Pull Force
The force depends on several factors, such as coil power, magnetic flux density, and input voltage. Typical force ranges from 100g to 5000g.
Recommendation:
For high-force needs, choose models with shorter strokes and higher power.
For longer strokes, ensure the solenoid provides enough force to actuate the mechanism.
Note: The force is strongest at the beginning of the stroke and decreases as the stroke progresses. This must be accounted for during mechanical design.
(1) Voltage Selection
Common DC solenoid voltages:
- DC 6V, 12V, 24V, 48V
- AC 110V, 220V (less common, typically for special-purpose applications)
Recommendation:
- For battery-powered systems, use DC 6V or 12V solenoids.
- For industrial systems, DC 24V is widely used due to its reliability and safety.
- DC 48V or higher is suitable for high-force equipment (e.g., motorized valves), but consider wire gauge and copper availability.
(2) Power (Wattage) Selection
Power affects solenoid efficiency and heat generation:
- Low Power (1–5W): Suitable for intermittent operations such as smart locks or micro valves.
- Medium Power (5–20W): Ideal for industrial automation, conveyors, fitness equipment, etc.
- High Power (20W+): Required for high-force applications like heavy door systems and automated production lines.
Note:
- High-power solenoids require good thermal management to prevent overheating.
- For continuous operation, consider models with energy-saving features, such as pulse drive (which reduces current after activation to lower heat).
Size and mounting method are critical when selecting a solenoid:
Verify mounting hole distances and installation types (screw-in, welded, snap-fit).
Ensure the direction of the plunger stroke matches the mechanical design and fits within the installation space.
Recommendation:
- Choose solenoids with compact housing and customizable brackets if space is limited.
- For replacements or upgrades, match existing size standards to avoid redesigning the structure.
When the solenoid is used for long periods or in continuous-duty applications, durability and heat dissipation are critical factors.
(1) Durability
- Prolonged activation can lead to coil burnout, performance degradation, or material fatigue.
- Choose solenoids rated for continuous duty (100% ED), indicating they can be energized continuously without overheating.
(2) Thermal Design
- Solenoids generate heat during operation. Without proper heat management, the coil’s lifespan may decrease.
- Look for designs with heat sinks, ventilation slots, or external cooling mechanisms (e.g., fans or heatsinks).
Recommendation:
For high-frequency or long-duty cycles, select models with:
- Low resistance coils (to reduce I²R losses),
- Pulse-width modulation (PWM) drive or pulse-hold circuits (to lower power after activation),
- Certifications or product testing indicating long-term reliability.
Note:
Thermal performance also depends on ambient temperature and mounting orientation. Ensure the solenoid’s rated temperature range matches the operating environment.
When used in special environments, it is necessary to select solenoids with appropriate protection ratings:
(1) Dustproof and Waterproof (IP Ratings)
- IP54: Dust-protected and resistant to water splashes; suitable for general industrial environments.
- IP65: Completely dust-tight and protected against low-pressure water jets; suitable for outdoor equipment.
- IP67: Suitable for temporary immersion in water; ideal for high-humidity or underwater applications.
(2) High-Temperature Resistance Design
For applications in high-temperature environments, such as automotive components or baking machinery, it is necessary to choose:
- Coils rated for high temperatures (withstand above 150°C),
- High-temperature resistant materials, such as ceramic or high-heat-resistant plastic enclosures.
(3) Vibration and Corrosion Resistance
For use in environments with significant vibrations, such as automobiles, marine equipment, or industrial machinery, it is recommended to select:
- Structures designed for shock resistance (e.g., reinforced coils, vibration-absorbing springs)
- Corrosion-resistant materials (e.g., stainless steel or galvanized enclosures).
Note:
Solenoids intended for use in specialized environments are often custom-designed and usually require custom mold development and production.