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Applicable scope

HLR3700-1-734 Motor starting relay is a compact, high capacity relay. Designed for general application to split phase and capacitor start, single-phase motors with start-winding current up to 25 amperes.

Key Benefits

• Reliable operation and long life independent of mounting position • Wide range of pick-up and drop-out ratings
• Start-winding current rating – 25 amps
• Small size for installation in compact equipment

• Economical

The HLR3700 relay utilizes a balanced armature to provide positive operation independent of mounting position. Double-break bonded Top-lay contacts provide excellent electrical and thermal conductivity to provide the high switching capacity and long electrical life. Silver cadmium oxide is used for the 25 amp contacts.

Mounting and Terminals

The HLR3700 relay’s compact size and universal mounting allow cost saving reductions in motor size and elimination of centrifugal switches. Mounting can be in the motor, in the conduit box, or remote from the motor. Calibrated in one position for a specific pick-up and drop-out, the HLR3700 remains within tolerance in all other mounting positions. A variety of mounting brackets, terminals and assembly screw extensions are available to meet any mounting requirements.

Pick-Up and Drop-Out Ratings
Ratings indicated maximum pick-up and minimum drop-out current limits. Pick-up is the current through the relay coil required to close the relay contacts. Drop-out is the current through the relay coil at which the contacts open. A production relay of a given rating will have a pick-up and drop-out current within the rating limit.

The HLR3700 relay coil is in series with the main winding of the motor and the normally open contacts are in series with the start winding. When voltage is applied to the motor, the in-rush current of the main winding through the relay coil creates a magnetic force which rotates the armature. This action closes the relay contacts and energizes the motor start winding.
As motor speed increases, the current in the main winding and relay coil decrease to a point where the armature biasing spring force is greater than the decreasing magnetic force, and the armature rotates back to its original position. This opens the relay contacts and disconnects the start winding.