Magnetic attraction

The power supplies are used in industry for powering and controlling electromagnets and electropermanent magnets, says Axima—with the company having sold more than 1,000 power supplies installed across the world.

The supplies allow the operator to control the electromagnet with fixed or continuous control of the magnetisation power, and fast demagnetisation of less than 4 seconds.

At the beginning of each magnetisation, the magnet is powered with reduced voltage to complete a load test, and the inverter will then set the magnet to maximum power only after the crane receives the lifting signal or the test time expires.

The electromagnets include a tipping function, through which the magnetic force can be smoothly reduced from 100% to zero—this is used for jettisoning unwanted material, explains the company. The tipping process can also be done in steps, with the level of magnetisation reduced by 20% each time the operator pushes a button.

The tipping and demagnetisation functions are blocked when the crane is moving or a lifting signal is received, to ensure safe operation.

Axima’s power supplies are designed to work with cranes to handle ferromagnetic materials, and are housed in painted sheet metal enclosures in high-quality industrial designs, says the company, suitable for placing and installing within the structure of the crane. The enclosure meets standard IP54, and features forced ventilation, air conditioning, and a heating system.

The switchboard panel includes power and control circuits, protective and switching elements, a PLC control system, and the battery section with accessories. The power and control of the electromagnet is provided by its own three-phase, four-quadrant control rectifier, which uses energy recovery in the mains and can therefore demagnetise the electromagnet more quickly, says Axima.

The heavy lifting electromagnets feature a back-up battery installed in addition to mains power supply, to provide back-up power in accordance with the EN 13155 regulation.

Any deviations from the nominal voltage are automatically detected in the even of a loss of one phase or a voltage drop, says the company, and an audio and visual signal is triggered. The backup power supply comprises VRLA gel batteries with a life-span of ten years, and the condition and integrity of the battery is automatically periodically checked and indicated on the PLC system.