Magnetic Lock Product

Overview

A magnetic lock (or mag lock) is a stationary electromagnetic door-locking device mounted on the door frame header. Unlike a strike lock, which acts on a moving latch bolt, a mag lock uses a powerful electromagnet to attract and grip a ferrous armature plate bolted to the top of the door itself. The magnetic force creates a mechanical bond strong enough to hold a standard single-leaf door against typical human push force.

Mag locks are among the most robust and tamper-resistant locks in physical security. They offer no latching mechanism, no moving parts under load, and no mechanical adjustments—the holding force is purely magnetic attraction between the coil and the armature. They are widely deployed on high-security facilities, hospitals, data centers, and emergency exits where reliability and simplicity matter more than the continuous power draw.

How it works

The [[magnetic-lock-electromagnet-assembly|electromagnet assembly]] contains a multi-turn [[copper-winding|copper coil]] wound around a laminated [[motor-housing|iron core]]. When 24 VDC is applied, current flows through the coil, generating a magnetic field. The strength of this field is proportional to current and coil turns; typical units produce 3000–5000 N of holding force when fully energized.

The [[magnetic-lock-armature-plate|armature plate]] is a hardened steel rectangle bolted to the top edge of the door. When the electromagnet is energized, the iron armature is attracted toward the magnet's pole face and held in firm contact. This magnetic attraction creates a mechanical lock independent of any mechanical latch or strike.

The force is purely attractive and holds the armature passively; no solenoid plunger or mechanical keeper is required. This simplicity eliminates the mechanical wear, adjustment, and failure modes of strike locks. The [[magnetic-lock-mounting-brackets|mounting brackets]] ensure the magnet and armature remain parallel and aligned within the nominal 6–8 mm working gap.

Fail-safe and fail-secure operation

Like strike locks, mag locks can be configured in two modes, controlled by the [[magnetic-lock-fail-safe-mechanism|fail-safe mechanism]]:

• Fail-safe: When power is removed, an internal spring-loaded release lever mechanically separates the magnet from the armature, allowing the door to swing open. This mode is required on life-safety doors (fire exits, stairwells) to ensure occupants can evacuate during a power outage.
• Fail-secure: No mechanical release; the door remains locked until 24 VDC is actively applied. Loss of power locks the door permanently until power is restored and the magnet is re-energized. This mode secures high-security access points (server rooms, vaults, executive offices).

A fail-safe mag lock typically includes a secondary solenoid that acts as a mechanical release latch. When the main magnet is de-energized, the secondary solenoid is spring-loaded to the RELEASED position, pushing the armature away from the magnet. This ensures that occupants cannot be trapped if power fails.

Electrical characteristics and power management

The electromagnet coil is inductive; when 24 VDC is first applied, inrush current can be 3–5 times the steady-state holding current. Protection circuits in the [[magnetic-lock-power-supply|power supply module]] include:

• Current limiting resistors or active current limiting to reduce inrush stress on the power supply.
• Transient suppression diodes across the coil to absorb voltage spikes when the magnet is de-energized.
• Thermal fuses that open the coil circuit if temperature exceeds 80–90 °C (preventing runaway overheating).

Continuous power draw for a typical mag lock is 20–30 W, higher than strike locks. Large installations often use separate 24 VDC supplies for mag locks to prevent voltage sag that affects reader circuits or control panels. Some systems use "buzz" mode: the controller energizes the magnet only during the door release window (e.g., 5–10 seconds) to reduce power consumption and heat generation.

Installation and mechanical design

The electromagnet mounts horizontally on the door frame header, directly above the door opening. The armature plate mounts on the top edge of the door, aligned with the magnet pole face. Proper alignment is critical: even 2–3 mm misalignment can reduce holding force by 30–50%. The [[magnetic-lock-mounting-brackets|mounting brackets]] provide shims and adjustment slots to fine-tune alignment.

The [[magnetic-lock-status-module|status module]] includes a [[hall-sensor|Hall sensor]] or reed switch that detects whether the armature is in contact with the magnet. This sensor provides feedback to the access control system: if the door is held closed, the sensor indicates "locked"; if the armature separates (door forced open or magnet de-energized), the sensor shows "unlocked."

For exterior or wet-environment installations, the magnet enclosure is stainless steel or powder-coated aluminum. The [[magnetic-lock-cable-harness|cable harness]] uses UV-resistant insulation and shielded twisted pair to prevent voltage drops over long runs (more than 30 meters).

Advantages and limitations

Mag locks excel in high-security and high-traffic scenarios:

• No moving latches: No mechanical wear, adjustment, or alignment issues over millions of open/close cycles.
• Simple, robust: Fewer components means fewer failure points and lower maintenance.
• Powerful: 5000 N holding force resists forced-entry techniques like ramming or prying.
• Retrofitable: Can be installed on standard hinged doors without modification.

Limitations include:

• Power consumption: Continuous 24 VDC draw (20–30 W) is higher than strike locks; requires robust backup power for fail-safe operation.
• Visible exterior magnet: The electromagnet is mounted openly on the door frame, making it a visual security indicator (both a feature and a vulnerability).
• Armature gap sensitivity: The magnetic force drops sharply if the armature separates by more than a few millimeters, requiring precise alignment and periodic maintenance.
• Sustained force only: The magnet cannot function as a lock if the door is already open and the armature removed; it is only useful when holding a closed door.

Maintenance and diagnostics

Periodic cleaning of the magnet pole face and armature surface prevents dust and oxidation from reducing holding force. A corrosion layer or magnetized dust can weaken the magnetic bond by 10–20%.

The [[magnetic-lock-status-module|status sensor]] should be tested regularly to ensure it reliably detects the locked state. A faulty sensor can result in false "unlocked" signals, causing alarms or access denial even though the door is physically held closed by the magnet.

Power supply monitoring is important: if the supply voltage drops below 18 VDC, holding force degrades significantly. Many modern controllers include voltage supervision and will trigger an alarm if mag lock voltage strays outside acceptable limits.