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Full wave/AC vibratory feeders can reduce power consumption by as much as 40 to 60 per cent if used instead of conventional DC/half-wave feeders, according to Elscint.

Half-wave electromagnetic vibratory feeders operate with an inefficient attract-release system.

A spring-mounted moving mass is alternately attracted by a rectified pulsating direct-current electromagnet (requiring a high-power consuming rectifier) and springs return it to its original position.

The full-wave AC-operated variable-speed electromagnetic drive system incorporates a magnet (part of a spring-mounted moving mass).

The poles of the magnet are intermeshed with those of an electromagnet, which is powered directly by an alternating current line.

This results in the spring-mounted moving mass being equally attracted and repelled by the full wave/AC electromagnet on each half of the AC cycle.

The poles of the magnet are intermeshed in the air gaps of the AC electromagnet.

The polarity of the magnet is fixed, while the polarity of the electromagnet alternates at line frequency.

The electromagnet polarity is shown as it exists on one side of the AC sine wave.

Both poles of the magnet are attracted towards the unlike electromagnet poles, while being repelled in the same direction by the like poles.

Thus, four forces are acting together to drive the armature and moving mass in the same direction.

This action has the effect of progressively closing the magnetising circuit through the electromagnet core, providing a progressively increasing magnetising force upon the magnet.

The demagnetising force is minor, since the action described also has the effect of progressively opening the demagnetising circuit.

On the opposite side of the sine wave, the polarities of the electromagnet are reversed.

The armature is driven in the opposite direction and a net magnetising force once again acts on the magnet.

A predominant magnetising force always works upon the magnet, which prevents it from losing its strength.

Full wave/AC drive feeders are highly accurate – since the amplitude of the feeder’s vibration depends directly upon the forces applied at the poles – and since these forces depend directly upon the applied AC voltage, a simple variation of the AC voltage from zero to 100 per cent results in a corresponding amplitude variation from zero to 100 per cent.

With a half-wave or DC vibratory feeder, a 10 per cent increase in voltage may result in a 40 per cent increase in feed; with a full-wave or AC drive feeder, a 10 per cent increase in voltage results in a 10 per cent increase in feed.

This level of accuracy makes the feeding much easier to control.

Full wave/AC vibrators do not require a rectifier, which means they consume less power, resulting in energy savings of up to 60 per cent.

Full wave/AC vibrators require less maintenance, as the vibrations are smooth and not jerky, resulting in fewer breakages.

The smooth vibrations are most suitable for fragile and lightweight components.

Though there are advantages such as increased feed accuracy, energy savings and lower maintenance requirements, there are no disadvantages or trade-offs in speed or capacity.

The full-wave drive feeders can handle light as well as bulky and heavy components at high speeds.

However, while the full-wave/AC drive units provide increased feed accuracy, energy savings and lower maintenance requirements, there are no disadvantages or tradeoffs in speed or capacity.

The full-wave/AC drive feeders can handle light, as well as bulky and heavy, components at high speeds.

Energy/power costs will continue to rise in the future as demand threatens to exceed the available supply.

Making even minor changes to a materials-handling operation can significantly reduce power consumption.

In many cases, using full wave or AC-operated variable-speed electromagnetic feeders instead of DC drive attract-release feeders can save energy and increase feed accuracy.

A full-wave/AC-powered vibratory bowl feeder with a rating of 780VA (with a diameter of 600 to 650mm) results in power consumption of 3.6 units per eight hours, while the equivalent half wave/DC-operated vibratory feeder would result in power consumption of about nine units per eight hours.

The savings can be monetised at 5.4 units per eight hours (146 units per month).

Elscint Automation

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