Description of the magnetic force generated by the DC electromagnetic coil and the AC electromagnetic coil

The stroke of the armature (air gap) has a great influence on the magnetic force generated by the electromagnetic coil. The larger the stroke of the armature, the smaller the magnetic force that lifts the armature. This relationship is also known as the itinerary-magnetic relationship.

In addition to the force generated by the spring, the pressure of the fluid also counteracts the force of a portion of the solenoid lifting the armature.
In the case where the effective power is the same, the stroke-magnetic curve of the DC coil is different from the AC coil. When the armature has moved the DC coil, the holding magnetic force is larger than that of the AC coil, but when the armature is not moving, the DC coil has a smaller magnetic force than the AC coil. Therefore, an AC coil should be used when the fluid pressure is high. If the geometry of the armature and the stop are specifically designed, the above disadvantages of the DC coil can also be overcome.

Other features of the two electromagnetic coils include:
DC electromagnetic coil
■ Low noise
■ Small armature wear
■ The resulting magnetic force is large
■ The suction power is the same as the power retention
■ No need for short circuit AC solenoid
■ Easy to produce noise
■ Risk of burnout when the armature is blocked
■ Switching speed is faster (related to phase angle)