A solenoid is an electro-mechanical device which coverts electrical energy into linear motion. Current passed through a coil of insulated copper wire produces a magnetic filed which moves a steel plunger located within the core of the coil. Steel parts surround the coil and contain the flux path for maximum pull or push force.
The desired attraction force can be obtained.
The attraction force matching to the actual load can be obtained by changing the shaped of the mating sections of the movable and stationary iron cores.
The exciting current is constant regardless of the stroke.
The exciting current of an AC solenoid varies depending on the stroke. With a DC solenoid, however, the exciting current is determined by DC resistance only and is constant regardless of the stroke.
Operation noise is reduced.
If there is a clearance between the movable and stationary iron cores of an AC solenoid, the coil may be burnt. In the case of a DC solenoid, its exciting current is constant regardless of the clearance of the movable and stationary iron cores. Therefore, a shock-absorbing material can be provided between the movable and stationary iron cores to reduce operation noises.
No beat noise is generated.
DC solenoids do not generated the beat noise AC solenoids generate due to the pulsating attraction force.
Constant operation time.
The operation time of the DC solenoid is constant regardless of the frequency. This is because it is driven by direct current.
Long life is ensured.
The service life of the solenoid depends greatly on the amount of mechanical wear between the movable iron core and the guide(pipe). The sliding section of the guide is specially treated to extend its service life.
The solenoid is an electromagnetic part that converts electric energy into mechanical linear movement. As the demand for automatic control equipment increases, solenoids are used more and more in audio equipment, Video equipment, Office equipment, Household electric appliances, Vending machine, Cars, Warning devices, Amusement equipment, etc.
A standard solenoid consists of :
1) Steel frame and shell which surrounds the coil and directs the flux path.
2) Coil which creates the magnetic lines of force.
3) Plunger which reacts the magnetic pull and moves to the coil against a stop.
1) Pull or Push
Linear Solenoids are designed to pull the plunger with sufficient force to move a connecting load. The same principle can be applied to perform push operation by adding a non-magnetic rod or push bar to the plunger and extending through the opposite end of the solenoid.
2) Stroke
Stroke is the airgap between the point where the plunger movement begins and where it seats a stop.
Solenoid will operate at any stroke up to maximum. Design for the shortest possible stroke is desirable for the greatest efficiency and minimum wear to prolong service life.
3) Force
Select a solenoid with adequate force at any point of the stroke at 85% of the indicated line voltage.
An overpowering force can result in plunger hammering that materially shortens solenoid life.
4) Duty Cycle
DC SOLENOID is used continuously or intermittently depending on the application.
Power consumption is determined by the duty cycle and operation time(Maximum power ON time) for each cycle.
If the maximim power ON time in one cycle exceeds three minutes, the operation is regarded as continuous This judgement differs slightly depending on the shape of the solenoid.
5) Insulation Class
Allowable maximum temperature values for the corresponding insulation classes are determined as shown in the table below according to the insulation class of the electric equipment. Solenoid must comply with this standard.
Normally, solenoids are categorized as insulation class A. In this class, the continuous rating of the exciting power is determined so that the allowable coil temperature rise is 65℃ when the ambient temperature is 40℃. Contact us if you desire a different ambient temperature or insulation class.
Insulation Class Y A E B F H C
Allowable maximum
90 105 120 130 155 180 MORE THAN 180℃
6) Change in attraction force in relation to temperature
The attraction force drops as the temperature rises. This is because the coil resistance increase and the ampere turn (AT) decreases as the temperature rises. When the coil temperature changes, the coil resistance change in relation to the temperature coefficient obtained as shown below.
7) Change in attraction force in relation to the shape of the plunger
The performance of the DC solenoid depends on the shape of the attraction section of the movable plunger. Generally speaking, the following relationship is obtained between the plunger angle θshown below and the stroke, although this relationship may differ depending on the size of the solenoid.
    θ= 45°or less ……………… 4mm stroke or more
    θ= 90°or more …………… 1 to 2mm stroke
    θ= 180°……………………… 0 to 1mm stroke
If both the attraction force and the force at a certain stroke are used, the plunger having the step shown below may achieve better results.
8) Effect of residual magnetism
Even when the magnetic field applied to the solenoid is removed, magnetism remains to some extent depending on the chemical components of the material and the strain caused during the forming of the material. This residual magnetism may prevent the attracted movable plunger from returning, causing problems during operation. Therefore, the magnitude of the residual magnetism should be considered an important factor when selecting solenoid.
MOTION takes many steps to reduce residual magnetism. Please let us know your application conditions eforehand.
Determine operating voltage.
Determine stroke(Linear movement) needed.
Determine the force required.
Select one or more series of solenoids that fit the stroke and force needed in the application.
Review the parameters of the particular MOTION solenoids given in the detail description of the solenoid series.
Make a final selection based upon the stroke, force, duty cycle and space limitation and other special performance faction..
If you are in doubt, or if you don't find a solenoid to fit your needs, MOTION application engineers will help you with the selection process. For unusual custom applications, MOTION will modify standard solenoids or design.
After the plunger is attracted, the ordinary DC solenoid must remain energized to maintain the attraction condition. MOTION's energy-saving self-sustaining solenoid incorporates a permanent magnet in the magnetic circuit so that the attraction, sustain and return are controlled by electrical pulses.
No electric power is necessary during sustain.
Once the plunger is attracted, the strong attraction force is maintained without electric power.
Rises in the solenoid temperature are minimal since the solenoid is controlled by electrical pulses.
The magnetic characteristics of the magnet remain unchanged even when used for extended period of time.
the self-sustaining solenoid us interchangeable with ordinary DC solenoid since they are identical in shape.