Rev. A.3, 5/00 | Page- 13 |
3. ELECTRICAL INSTALLATION
3.1 GENERAL ELECTRICAL CHARACTERISTICS
The Magnalock constitutes a low current electric load. Owing to internal circuitry, the Magnalock does not show the normal characteristics of an electromagnetic or other inductive load. Inductive kickback is suppressed, so arcing across switch contacts need not be a concern. This suppression also protects nearby access control or computer equipment from possible interference. The circuitry performs the additional functions of canceling residual magnetism ("stickiness" on release) and accelerating field collapse so that the Magnalock releases nearly instantly when power is removed. Electrically speaking, the load is nearly pure resistive in nature although there is a modest capacitive component which depends on the series. The following chart shows the current draw for each version and the degree of internal capacitance.
| 32 @ 12V | 32 @ 24V | 34 @ 12V | 34 @ 24V | 62 @ 12V | 62 @ 24V | 82 @ 12V | 82 @ 24V |
|
|
|
|
|
|
|
|
|
CURRENT | 300 mA | 150 mA | 350 mA | 175 mA | 250 mA | 125 mA | 350 mA | 175 mA |
|
|
|
|
|
|
|
|
|
CAPACITANCE | 0 | 0 | 0 | 0 | 30 Mfd | 15 Mfd | 30 Mfd | 15 Mfd |
|
|
|
|
|
|
|
|
|
Capacitance can be an issue if very sensitive switch contacts are used to control the Magnalock (such as a low current reed switch). A capacitive load includes some inrush current which can stress these contacts. Note however that the problem is diminished when the Magnalock is mounted some distance from the control switch as the interconnecting wiring adds a series resistance to the circuit which sharply limits the inrush.
3.2 STANDARD LOCK
For operation, DC voltage must be provided to the lock. The red wire receives +12VDC or +24VDC, and the black wire, 0V (negative). If the lock is connected with reverse polarity, it will not function at all. The voltage source may be regulated, filtered or pulsating DC (transformer + bridge rectifier). Half wave pulsating DC generated by a transformer and single diode will not properly operate the Magnalock. An exact voltage level is not necessary. Less than standard voltage will proportionately reduce holding force but will cause no harm. Overvoltage up to 30% is acceptable.
The model 34, 62 and 82 series Magnalocks are dual voltage units. This means that you can apply either 12 or 24 volts to the same unit and it will operate equally well. Dual voltage Magnalocks are
It is good practice to use power supplies with 1/3 extra capacity beyond the current requirements of the load. This greatly reduces the possibility of heat induced power supply failure and also allows for future expansion. Power supply cost is a small fraction of the job cost and should not be skimped on.
Switches may be wired as necessary between the Magnalock and power source. Internal circuitry eliminates inductive kickback, so neither electromechanical switches nor solid state devices will be damaged by arcing when the Magnalock is shut off.
3.3 AVOIDING POOR RELEASE CHARACTERISTICS
One of the exceptional features of Magnalocks is near instantaneous release. This is particularly valuable when the lock is being switched off and the door is being opened at the same time as occurs when a switched exit device like Securitron’s Touch Sense Bar is being used. Two separate wiring errors can however cause Magnalocks to release slowly (in one or two seconds) and this is annoying.
The first problem is connection of a reverse diode in parallel with the lock's power input. This is often done to suppress inductive kickback from a coil such as a relay coil or solenoid. Magnalocks already have internal inductive kickback protection, so addition of a reverse diode is pointless. The diode does act to "recirculate" current flow through the magnet coil and thereby considerably slows release. A diode should never be connected as shown in Figure 12.