- Lifting Magnet
- Electro Magnet
- Power Supply & Control System
- 1. Power Supply System
Silicon rectifier system :
With this system, DC 220V is obtained by full-ware rectification of a single-phase or
three-phase AC supply, using silicon rectifier. System is compact, light in weight,
and easy to use, so maintenance is easy.
Thyristor(SCR) system :
AC is rectified to DC by thyristor. This system enables to control the number of
steel plate being lifted, by virtue of stepless voltage adjustment.
Constant-voltage control system :
The excitation of the lifting magnet is controlled by swiching on and off DC 220V
constant voltage supply to the magnet.
The magnetomotive force of the magnet cannot be varied.
Variable voltage control system :
The magnetomotive force of the lifting magnet can be varied by altering the excitation voltage.
Over-excitation control system :
In this system, an over-excitation is applied to the magnet coil when initial attraction
of the load material is to take place. When the actual handling of the load takes place,
the coil voltage is reduced.
This method results in decreased magnet power consumption, and increases
the effective lifting capacity of the magnet.
2. Power Interruption Protective System
This system provides for maintaining the hold on a lifted object for a certain duration
in the event of off-power. If the power supply fails, power is immediately supplied
from a battery, and a horn sounds.
Standard holding durations are 5, 10, 15 and 20 minutes, and leadacid batteries are normally used.
With this system, batteries and battery charging equipment are necessary.
3. Magnet Selection
Two or more magnets are installed on a single crane to handle long length of material
such as steel plate. In this case, it is necessary to select which magnets are
operated at one time, due to different shapes of load material.
For this purpose, a lifting magnet selector is available, providing simple and quick selection.