DEMAGNETISERS / MCD & MCDa SERIES PRODUCT DESCRIPTION

Overview

The magnetising and demagnetising fields are produced in a fixture or coil using a capacitance discharge technique.

Both series are microprocessor controlled with adjustable capacitor voltages from 50v to maximum (in 1v steps) with feedback via a digital display.  The microprocessor controls the charging and discharging of the machine ensuring that the charging is managed in a way to reduce the initial charge current that non-microprocessor systems may not have. The microprocessor also performs fault monitoring for system protection.

Each magnet charger demagnetiser is fitted with an internal dump resistor to discharge the main capacitors in power down or abort mode, ensuring a safe environment for both operator and machine.

All MCD units have the ability to interface with external PLC controllers via a digital interface as well as an RS232 port for integration with other products such as Integrating Fluxmeters or Gaussmeters.

The MCD series (as defined by the energy output, in joules, to the demagnetising fixture i.e. MCD4kJ), which is based on electrolytic capacitor technology, is suitable for low and medium production rate.  The typical range of energy outputs for the above series span from 750J to 20kJ, at capacitor voltages of up to 800 volts.

The MCDa series, which uses non-electrolytic capacitors, is capable of high production rates.  The typical range of energy outputs for the above series span from 100J to 20kJ, at capacitor voltages of up to 3,000 volts.

Principles of Operation

In most applications, the required current is too large to be directly driven from the mains and/or the fixture’s inductance/resistance is such that not enough current would flow to produce the required magnetic field.  A capacitor bank is therefore charged to the required voltage level (up to 3,000 volts) and this stored energy is then discharged by a thyristor into the fixture to produce the required magnetic field.

In a magnetising operation a clamp or freewheel diode may be placed across the fixture to ensure no reverse energy charges the capacitor bank negative.  All the energy is dissipated into the fixture as a magnetisation pulse.  Some MCD series units may not use a freewheel diode and only apply a unidirectional pulse.

For the setting operation the capacitor bank is again charged, to a lower voltage level, and this time the energy is fired through the fixture in reverse.  Only a unidirectional pulse is used.  This partially drives the magnet down its demagnetisation curve.

Ignitron Outputs

Ignitron outputs will be offered instead of semiconductor devices if the peak current is exceedingly high and/or the rise time of the pulse is very short.

Ignitrons may also be offered for machines where the fixture is “unknown” or where fault conditions are expected that could damage semiconductor output devices.

User Interface

Both MCD and MCDa series feature an easy to use control panel that includes:

• Four Buttons Operation Control
  • Pulse (Green) – to initiate a magnetisation cycle
  • Abort (Red) – to abort the current sequence
  • Up and Down (Yellow) – allows the adjustment of system voltage.
• LCD display – shows the current voltage level, status and error messages
• Key switch – available as an option to lock the adjustment buttons
• PLC interface – allows integration with automated production lines
• RS232 interface – optional extra

Magnet Charger Demagnetiser Energy

Magnet charger demagnetiser energy will be selected to meet the requirements of the application and will be dependent on the fixture design.  Typically, due to the high cost of energy storing capacitors, the higher the energy needed to satisfy the magnetising application, the higher the cost of the equipment.