Electromagnetic “mag” locks provide a Fail Safe locking mechanism, which requires power to maintain the holding force. For most applications, they secure a door for the purpose of traffic control. The mag lock is placed either onto or into the doorjamb, usually along the header.
An electromagnetic lock provides its greatest holding force when the door must pull away from the magnet. For a swing type door, the mag lock is placed adjacent to the lock edge of the door, requiring the door face to be pulled directly away. For a sliding door, the mag lock is placed on the locking leg of the doorframe. When the door is closed, the edge contacts the mag lock. To open, the door must be pulled directly away from the magnet.
The magnetic portion of the conventional electromagnetic lock is made up of many “E”-shaped thin ferrous metal plates placed adjacent to each other, creating a wide “E”. Lying on their back, they form the three metal lines on the face of the magnet. The size and the number of the “E” shaped plates partially determine the holding force of the electromagnetic lock. A copper wire winding creates the magnet field that results from the flow of Direct Current (DC). Electronics are installed to complete the circuitry.
All components are placed into a housing. A non-ferrous potting mixture fills the cavity and encapsulates the components. When the mixture hardens, the surface is machined flat to ensure maximum holding force. Most electromagnetic locks’ ferrous metal surfaces are then plated to protect against corrosion and increase durability. Some mag locks have a separate compartment for the wire connections and circuitry.
A ferrous metal strike plate or armature assembly slightly larger than the surface area of the electromagnet completes the locking mechanism. When powered, this spring-loaded plate is drawn flush against the electromagnet. The oversized strike plate provides sufficient surface area if there is settling or wear, protects against tampering and can resist removal of the mounting screws.
For commercial and institutional applications, mag locks are normally 12-24VDC powered electromagnets. The amperage draw ranges from approximately 125mA to more than 500mA at 24VDC, and 230mA to more than 600mA at 12VDC. The magnet size, holding force and construction determine the draw. The low amperage draw makes a simple single-door system capable of being operated by a .5Amp plug-in power supply.
The basic electromagnetic lock designed for a door is available with a holding force ranging from about 400 lbs. to a hybrid model with 4,000 lbs. combined holding force. Construction of the door and the jamb determine the holding force required.
Another electromagnetic lock category is asset management locks, smaller mag locks designed to secure showcases, cabinets, desks, etc. Access for these locks can include keypad/credential readers or remote release, eliminating the need for keys or cards.
Electromagnetic locks have been developed to incorporate just about every configuration of swing and sliding doors, including gates. Mag locks are available for top and side mount applications. They will have mounting holes in the face for rear mount. For top mount electromagnetic locks, there are two options: holes through the body of the magnet or an adjustable mounting bracket.
For double-door applications, two electromagnetic locks can be installed into an aluminum housing, providing a cleaner and more secure installation. A double door example is the Camden CX-92S-12, which has two 1200-pound surface mount mag locks.
Recessed Mag Lock Applications
Recessed mag lock applications are generally for sliding doors. The recessed application conventional electromagnetic lock can be installed into the locking leg of the doorframe. The Dynalock 2600 Series 650 lbs. holding force mag lock has a narrow backset to accommodate shallow openings. The recessed mag lock contacts the door only when closed.