Game, Set and Latch

July 23, 2021

The explosion of electric vehicle (EV) development has OEM design teams searching for ways to reduce power consumption for all vehicle components and systems. Efficiently utilizing the finite amount of energy available from an EV’s batteries is crucial for achieving maximum vehicle range, and this means every single component and system must be as lightweight and energy efficient as possible.

Failsafe Package
Failsafe control moves the armature into the safe position if power is lost

Electromagnetic components are used extensively in EVs. Replacing conventional solenoids with solutions utilizing latching technology is a great way to achieve the desired energy savings. Latching solenoids are ideal for any application that does not require a high cycle rate because they draw no power in order to maintain either an open or closed state.

While conventional solenoids require power during the entire ON cycle, latching solenoids require only a pulse of power to change state. Once the armature is extended or retracted, no power is consumed for the duration of the ON cycle because the armature in a latching solenoid is held in position either by a permanent magnet or residual magnetism (depending on the solenoid’s design).

The low power consumption of latching solenoid technology yields other benefits. Because there is no power consumption during most of the ON cycle, a higher current pulse can be used to actuate the armature, resulting in faster operation and higher force, without the excessive heat generation associated with conventional solenoids. Additionally, because the higher pulse current can generate more force, it is possible to utilize a smaller, lighter solenoid than would be needed if a conventional solenoid were used.

Latching solenoids consume no power, produce no heat, and generate no electrical noise to hold state.

Until recently, some OEM design teams have had concerns with using latching solenoids in applications where the actuator must return to a known position in the event of power loss. Because latching solenoids require power to actuate, a loss of power means that the armature will remain in its last commanded position.

This concern is easily settled with the use of a latch release circuit: a simple failsafe control strategy consisting of a circuit board and a capacitor. The circuit board monitors power availability, and the capacitor provides the necessary pulse of current to move the armature in the event of power loss. This system can be customized to actuate the armature to a predetermined, specific position.

Latching solenoids are the best solution for electric vehicle OEM design teams where high cycle rates are not required. Only a pulse of power is needed to actuate the solenoid, and no power is drawn to maintain a commanded state. They can also be smaller and lighter than conventional solenoids. The addition of a customizable failsafe circuit means that in the event of power loss, the solenoid can be actuated to its safe position.

This article was originally published by International Transport Manufacturer in July 2021

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