Electromagnetic lock

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The electromagnetic , magnetic keys , or maglock keys are locking devices consisting of electromagnets and armature plates. There are two main types of electric lock devices. Locking the device may be either "safe fail" or "unsecured failure." Fault-secure locking devices remain locked when power is lost. Unsecured locking devices are unlocked when not energized. Direct pull electromagnetic keys are inherently fail-safe. Usually the electromagnet part of the lock is attached to the door frame and the married amber plate is attached to the door. Both components are in contact when the door is closed. When the electromagnet is energized, the current passing through the electromagnet creates a magnetic flux that causes the armature plate to pull into the electromagnet, creating a locking action. Because the electromagnet marriage area and armature are relatively large, the forces created by the magnetic flux are strong enough to keep the door locked even under pressure.

A typical single-door electromagnetic lock is offered in both  £ 600. (272 kg) and  £ 1200. (544 kg) dynamic carrying capacity. The "fail safe" magnetic lock requires power to stay locked and is not usually suitable for high security applications as it is possible to disable the lock by interrupting the power supply. However, by adding magnetic bonding sensors to the key and by using a power supply that includes battery backup capabilities, some higher specific security applications can be implemented. Electromagnetic locks are particularly suitable for use in emergency exits that have fire safety applications because they do not have moving parts and are therefore less likely to fail than other types of electrical locks, such as electric strikes.

The current magnetic lock strength is proportional to conventional door locks and is cheaper than conventional bulbs to operate. There is an additional piece of removal hardware installed in a typical electromagnetic locking system. Because the electromagnetic key does not interact with the lever or door knob on the door, it is usually a separate release button that cuts off the key power supply installed near the door. This button usually has a timer, once the button is pressed, keeps the lock unlocked for 15 or 30 seconds according to the NFPA fire code. Additionally a second release is required by the fire code. Either a motion sensor or a collision blade with an internal switch is used to unlock the door on the exit side of the door automatically.

Video Electromagnetic lock

History

The first modern direct-tune electromagnetic lock was designed by Sumner "Irving" Saphirstein in 1969 for early installation on the door at the Montreal Forum. Fears of fire by local authorities in door locking in the Forum prompted management to find a locking solution that would be safe during a fire incident. Saphirstein initially proposed to use a linear door holder pile to work as an electromagnetic key. These door holders have traditionally been used to hold open doors, but in this application Saphirstein believes they can be packaged and adapted to work as fail-safe keys. After successful prototypes and installations at the Forum, Saphirstein continues to evolve and improve design and establish the Locknetics company to develop accessories and control circuits for electromagnetic locks.

In difficult business conditions, Locknetics is then sold to the Ives Door Hardware company and then resold to the Harrow company. Long later this division was later sold back to Ingersoll Rand Security Technologies. The division was recently closed and moved to another division within Ingersoll Rand Security. Employees associated with the activities at Locknetics, continue to form other key electromagnetic companies, including Dynalock Corporation and Security Engineering Co.

Saphirstein continued to develop electromagnetic locking technology at other companies he pioneered including Dortronics (later purchased by Sag Harbor Industries), Delta Controls (first purchased by Lori Lock Company and then purchased by Hanchett Entry Systems) and Delt-Rex Door Controls, all located in Connecticut. Other engineers also left these companies to form their own manufacturing companies in electronic locking, including Highpower Security Products LLC in Meriden, Connecticut. Many other companies both in the US, Canada, and throughout Asia were later established to create additional product offerings for direct tensile electromagnetic locks.

Maps Electromagnetic lock

Principles

The principle behind the electromagnetic lock is the use of electromagnetism to lock the door when energized. The strain force should be chipped with load, and armature locks and plates must face-to-face to achieve optimal operation.

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Operation

The magnetic lock depends on some basic concepts of electromagnetism. Basically it consists of an electromagnet pulling a conductor with considerable force to prevent the door from opening. In a more detailed examination, the device makes use of the fact that current through one or more loop wires (known as solenoid) produces a magnetic field. It works in free space, but if the solenoid wrapped around a ferromagnetic core like soft iron, the field effect is strongly amplified. This is because the internal magnetic domains of the material are parallel to each other to greatly increase the magnetic flux density.

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Equation

Dengan menggunakan hukum Biot-Savart, dapat ditunjukkan bahwa kerapatan fluksi magnetik ${\ displaystyle B}  ÂÂ$ diinduksi oleh solenoid dengan panjang efektif ${\ displaystyle l}  ÂÂ$ dengan ${\ displaystyle I}  ÂÂ$ melalui ${\ displaystyle N}  ÂÂ$ loop diberikan oleh persamaan:

${\ displaystyle B = {\ frac {\ mu_ {0} \ mu _ {r} IN} {l}}}  ÂÂ$

Kekuatan ${\ displaystyle F}  ÂÂ$ antara elektromagnet dan pelat armatur dengan luas permukaan ${\ displaystyle S}  ÂÂ$ terkena elektromagnet diberikan oleh persamaan:

${\ displaystyle F = {\ frac {B ^ {2} S} {2 \ mu_ {0}}}}  ÂÂ$

Dalam kedua persamaan, ${\ displaystyle \ mu _ {0}} Â$ merepresentasikan permeabilitas ruang kosong dan ${\ displaystyle \ muR}} Â Â$ permeabilitas relatif dari inti.

Although the actual performance of magnetic keys may differ substantially due to various disadvantages (such as leakage of flux between electromagnets and conductors), the equations provide a good insight into what is required to generate strong magnetic keys. For example, the key strength is proportional to the square of the relative permeability of the magnetic core. Considering the relative permeability of a material may vary from about 250 to cobalt to about 5000 for soft iron and 7000 for silicon iron, magnetic core options can therefore have an important impact on magnetic lock strength. Also relevant are the choice of current, the number of loops and the effective length of the electromagnet.

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Technical comparison

Magnetic locks have a number of advantages over conventional locks and electric strikes. For example, their endurance and fast operation can make them valuable in high traffic office environments where electronic authentication is required.

Benefits

• Remote operation: Magnetic keys can be switched on and off remotely by adjusting resources.
• Easy to install: Magnetic locks are generally easier to install than other keys because no part is connected.
• Quick operation: The magnetic key unlocks instantly when power is cut, allowing quick release compared to other keys.
• Sturdy: Magnetic keys can also suffer less damage than a few blows than conventional keys. If the magnetic lock is forced open with a crowbar, it will often do little or no damage to the door or lock. No moving parts in the electromagnetic lock are to be removed.

Losses

• Needs a constant resource to be safe.
• May cancel power in case of power outage, disable security.
• Expensive compared to mechanical keys.
• Requires additional hardware for safe operation.

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Installation

Magnetic locks are suitable for swinging and swinging doors. Brackets (L bracket, LZ bracket, U bracket) are used to direct the armature for use with both applications. The filler plate is also used to provide a large and flat mounting area on the doorframe when the electromagnet is larger than the available mounting space on the door frame due to the frame geometry.

Magnetic locks should always be installed on the safe side of the door. Most installations are mounted on the surface. For safety, magnetic locks, cables, and cables should be routed through the door frame or flush mount with wire prints.

Installation is very easy. With swinging applications, the electromagnet is usually installed in the corner of the door in front of the door. Maglock can also be mounted vertically on the door when they are equipped with full length housing. With this configuration the armature is passed through the door and oriented to mate with the face of the electromagnet. Armature and electromagnet plates should be touched to provide locking locking strength.

With a swinging app, an electromagnet is usually mounted on the side of the door. In this configuration, the armature is mounted on a Z-shaped bracket that directs the armature to mate with the electromagnet.

Magnetic locks are almost always part of a complete electronic security system. Such a system may consist only of an attached or perhaps more complicated card reader, involving connections to a central computer that monitors building security. Whatever the choice of locking system, fire safety is an important consideration.

Other variations and improvements to the electromagnetic lock have been developed. The most remarkable is the shear key, in which the armature does not directly attract the face, but the load is precisely in shear, such as mechanical cessation. The sliding magnetic lock allows the door to swing in both directions, as opposed to the original (and now ubiquitous) direct pull type, which usually works either in swing or off-swing configurations. To provide a magnetic shear key with an appropriate retaining force, the two pins lock the armature to the magnet itself, and ensure that the magnet is locked in place.

The enhanced 'shear' electromagnetic lock was patented on May 2, 1989, by Arthur, Richard and David Geringer of the Security Door Control, an access control hardware manufacturing company. The devices outlined in their designs are in principle the same as modern magnetic keys consisting of electromagnets and armature plates. The patent does not make reference to electromagnet-making methods and some detailed variations on the design, including one that uses a spring armature plate to bring the armature plate closer to the electromagnet. The patent expires on May 2, 2009.

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Holding force

The magnetic lock has a metal plate surrounded by a magnetized wire reel. The number of reels determines the retaining force characterizing the key:

• Micro Size: 275Ã, lbf (1,220Ã, N) power hold.
• Mini Size: 650Ã, lbf (2,900Ã, N) withstand style
• Midi size: 800Ã, lbf (3,600Ã, N) power hold
• Standard Size: 1,200 Ã, Â £ lbf (5,300Ã, N) holding strength.
• Slide Lock: 2.000Ã, lbf (8,900Ã, N) withstand style

Standard size electromagnetic keys are used as gate locks.

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Electrical requirements

The power for the electromagnet lock is DC (Direct Current), about 5-6 W. The current is about 0.5 A when the supply voltage is 12VDC and.25A when using 24VDC (varies between manufacturers and if there are one or two coils in the block). It is also advisable to verify that the magnetic keys carry a UL mark. In general, the key specification of an electromagnet is a 12/24 VDC double voltage. If using a rectifier to change AC power, a full wave bridge rectifier must be used.

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Application mode

For security purposes, electric keys and electric strikes can be designed to operate in one of two modes:

Failure-safe - to protect people: Locks are released if power is lost.
Failure-safe (also known as non fail safe) - to protect property: Lock remains closed if power outage off. This type of lock has a cylinder, similar to that found on conventional keys. The cylinder allows the lock to remain secure, even though the power supply is disconnected.

The electromagnet lock is ONLY Safe-Failed, so it must meet the applicable fire regulations to be safe in an emergency situation.

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References

Source of the article : Wikipedia