Browse Prior Art Database

# Bipolar Magnet Drive for Reducing Residual Magnetism

IP.com Disclosure Number: IPCOM000089437D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 37K

IBM

## Related People

Weber, JA: AUTHOR

## Abstract

The residual magnetism in a magnet is reduced to an acceptable level by driving the magnet with a bipolar drive circuit.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 83% of the total text.

Page 1 of 2

Bipolar Magnet Drive for Reducing Residual Magnetism

The residual magnetism in a magnet is reduced to an acceptable level by driving the magnet with a bipolar drive circuit.

Fig. 1 shows a bipolar circuit for driving a device magnet. The bipolar circuit causes a short (approximately 20 msec) current pulse in the device magnet to eliminate any residual magnetism left by current which normally energizes the magnet.

Fig. 2 shows the input waveform to the circuit and the output waveform, generated by the circuit, which is applied to the device magnet. The A section of the input voltage generates the A' section of waveform, generated by the circuit, which is applied to the device magnet. The A section of the input voltage generates the A' section of the output which is used to activate the magnet. At the fall of the input, the circuit generates the B section of the output, which is of opposite polarity and of shorter duration than the A' section.

In Fig. 1 the duration of pulse B is controlled by the series combination of R(6), C(6), R(8). The drive circuit of Fig. 1 operates as follows: When the input is 0 volts, T(1) is on, T(2) is on, T(3) and T(4) are off, and no current flows in the device magnet. When the input goes to a positive value, for example, 12 volts, T(1) and T(2) are turned off, and T(4) turns on, causing current to flow from ground which energizes the device magnet.

When the input returns to 0 volts, T(1) and T(2) are turned on, causing the collector...