Peak & Hold Solenoid Theory

Peak and hold solenoids, also known as saturated switch solenoids, are utilized in place of constant current solenoids when the application requires any of the following:

  • Faster actuation times
  • Lower average power consumption
  • Lower heat generation
  • Smaller package size

Any or all of these requirements can drive the decision to use a peak and hold type solenoid.

Figure 1

Peak and Hold Large Graph

The peak and hold drive circuit applies a higher current to the solenoid while it is at its open or maximum air gap condition. Once the solenoid has completed its travel to the closed or minimum air gap position, the current is reduced to the hold current level, which maintains the solenoid in this position until the current is removed.

The current amplitude and time duration of the peak and hold drive signals are application dependent and are modified to match a given application.

A typical drive signal profile is shown in the graph. However, the "peak" duration could be as short as 1 or 2 milliseconds based upon the needs of the application.

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