3-Position Solenoids: General Technical Overview

​The 3-position solenoid allows a mechanism to be moved accurately to 3 stable points. For selection mechanisms this permits higher functionality to be achieved within a restricted space. The most common (standard) configuration is centre-neutral type which is described.

In the de-energised condition the armature is moved to the centre position by springs. If Coil 1 is energised, the armature moves out to the maximum extension, if Coil 2 is energised the armature moves in to the minimum extension. Because all 3 positions are controlled by mechanical stops, they are highly repeatable.

The solenoid comprises of two separate coil assemblies mounted end-to-end which move the armature to either end-position when energised, and a spring operated centring mechanism. The centring mechanism provides a positive centre position from which the armature will not move until deflection force exceeds the spring preload, so will not shift with small changes in load.

Control of the solenoid requires only two switches to regulate power applied to either coil. To achieve similar function with a conventional solenoid, two solenoids would be required, plus a complex spring and linkage mechanism.

To use a motor to achieve the same function, gearing and position sensing would be required, plus a more complex drive circuit. The 3-position solenoid provides a compact, robust, and elegant solution to such positioning requirements, with the simplest possible control circuitry.

The 3-position solenoid can be produced in open-frame construction, or in tubular construction. 3 different spring options are offered for most types, option A is standard and will work with any duty cycle, options B and C have stronger springs and will generally only work at intermittent duty cycle, refer to graphs for details.

General specifications:
Insulation class type E (120ºC), type A (105ºC) for leadwires
Isolation Voltage 1000 vAC, 50/60Hz, 1 minute
Insulation Resistance >100MΩ at 500vDC
Life Expectancy >200,000 cycles

Product Designation

Part numbers for 3-position solenoids are constructed as follows:
C3PT-0712 A
C3PT-07 12 A
Type designation Voltage (@100% duty) Spring Type

End-Neutral types

3-Position solenoids with end-neutral construction, where de-energised position is at one end of movement, and centre and other end position are achieved by energisation of the coils can be produced to customer request.