MAGNETISERS / MCSD PRODUCT DESCRIPTION

Overview

MCSD units are easily incorporated into automatic calibration systems and offer precision operation and high production rate performance.  The MCSD range also fully demagnetises many types of permanent magnet with an exponentially decaying sinusoidal waveform.

The MCSD series also has the ability to set or age magnets.  This takes the form of a uni-directional pulse of the opposite polarity to the magnetisation pulse.  This pulse knocks the magnet back along its hysteresis curve.  This can either be a fixed energy set pulse, for artificial aging, or a calibrated set pulse where a Fluxmeter or Gaussmeter provides feedback to the system.

Their easy to use versatility makes them ideal for laboratories needing to develop and support permanent magnet based products.  The MCSD range has 2x RS232 ports suitable for SPC data collection as standard and PLC control.

The MCSD unit is fully microprocessor controlled with adjustable capacitor voltage from 50 to 3,000v (in 1v steps) with feedback via a digital voltage display.  It utilises non-polarised capacitors that are discharged into a fixture or coil.  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 MCSD unit 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.

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 is placed across the fixture to ensure no reverse energy charges the capacitor bank negative.  All the energy dissipated into the fixture is a magnetisation pulse.

In a demagnetisation operation the free wheel diode is placed in parallel with the thyristor to cause a ringing or decaying sinusoidal waveform.

In set mode the freewheel diode is removed to provide a uni-directional pulse.

Reverse polarity circuits ensure that the energy can be discharged either way through the fixture to provide pulses of either polarity.

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

The MCSD series is controlled by means of a keypad during normal operation or via an RS232 / PLC port when under remote control.  Using four different modes of operation the MCSD series can quickly charge, demagnetise or when used with suitable external hardware (Gaussmeter / Fluxmeter) calibrate magnets.

Modes of Operation

• Charge Mode is used to charge (saturate) magnets using a uni-directional pulse of energies up to the maximum allowable.  The operator selects the operating voltage and the MCSD series discharges into the magnetising fixture whenever the pulse button is pressed.  The capacitor voltage is displayed on the front panel during this process and can be altered at any time to a new value.
• Demag Mode is used to demagnetise work pieces using a decaying sinusoidal waveform.
• Set mode is used to set the flux level of a work piece to a particular value.  This mode offers control of the demagnetising pulses.  Demagnetising pulses are generated starting with the minimum voltage, the operating voltage being increased automatically by the selected step size after each pulse up to the selected maximum.
• Cal mode is similar to set mode with the addition of an initial charge pulse of the maximum allowable energy. This pulse is used to saturate the work piece to a flux level greater than the final required flux level.  The sequence of demagnetising pulses that follow the charging pulse can then be used to set the magnets to a correct flux level in one continuous overall operation.

Using decaying sinusoidal wave forms to demagnetise or calibrate magnets will produce a more stable magnet than achieved through demagnetising with uni-directional pulses with a reversed polarity.

Programmable

The MCSD series has several memories in each mode that can be used to store different operating voltages.  These can be used to set up the machine quickly and easily for processing different production items.

At any time during operating the MCSD series can be forced to abort any operation currently in progress and enter a safe state. The capacitor energy is safely dumped into an internal dummy load and the machine becomes inactive until the operator continues using the machine.

To reduce unnecessary power consumption, the MCSD series has a built in automatic “timeout” function.  After three minutes of non-use the capacitor voltage is dumped and the MCSD enters a safe state.

Magnetiser Energy

The magnetiser energy will be selected to meet the requirements of the application and will be dependent on the fixture design.

The typical range of energy outputs for MCSD units span from 100J to 20kJ.

Options

• Auto Calibration
  The MCSD series can be interfaced to standard Hirst Gaussmeters and Integrating Fluxmeters for the purpose of auto calibration.  Using this type of system, after the initial preset values for output pulses are entered, the entire calibration of the magnet involves just one press of the PULSE button.
• SPC
  The MCSD can store information about each magnet, continuously uploading this data to a remote computer for analysis.  If a Gaussmeter or Fluxmeter is interfaced to the MCSD information such as final flux, calibration voltage etc can be collected for statistical analysis.
• PLC
  The MCSD series can be provided with a PLC port to provide remote operation of the unit using digital inputs and outputs.  The PLC control can be part of a mechanical handling system or integrated with a Hirst Gaussmeter or Integrating Fluxmeter to provide a fully automated system.