Logic Control

AC Current Relay— The AC current relay senses a preset current value and operates a SPDT relay whose contacts may be used in a control circuit. Unlike apparatus intended for motor or branch circuit protection, the current relay provides a continuously adjustable trip-current setting and automatic reset, making it suitable for control of machines.

Application Description
It is also suitable for protection of mechanical apparatus from jam-up or other overloading conditions that result in measurable increase in motor current.

Typical Applications

• Conveyor - Detect jam-up condi-ions. Initiate jam-clearing devices to correct conditions without tripping motor overload protection.


• Intermittent Use Conveyor - Sense load on conveyor. Shut off drive when no-load indicates there is no product to be moved.


• Belt and Gear Reductions - Detect loads sufficient to cause belt slip-page or shearing of output shaft. Initiate load reduction or shutdown.


• Water Lubricated Pumps - Detect no-load conditions indicating absence of water. Initiate shutdown to prevent burnout of pump bearings.


• Batch Process Mixers - Detect presence of first component. Initiate addition of second component. Continuous Process Mixers— Detect high (low) viscosity condition. Initiate rate change of viscosity correcting component.


• Machine Tools - Detect tool wear (high load) or breakage (low load). Initiate shutdown or signal maintenance.


• Saws - Sense high load. Initiate momentary reversal of feed to prevent motor protection from tripping.


• Electric Furnace or Oven - Sense low current conditions. Initiate loss of heat alarm before temperature drops.


• Special Lighting for Rush Hour Control - Sense total plant current draw. Initiate timed supplementary lighting to aid departing employees.