Definitions and Terminologies | TDS Co., LTD.

Here are the definitions and terminologies frequently used for solenoid production and operation.
Please feel free to contact us for questions.

・Solenoid	・Magnetomotive force
・ Keep Solenoid	・Temperature Rise
・Stroke	・Residual Magnetism or Residual Holding Force
・Pull Force	・Heat-resistant Classes (Insulation Classes)
・Holding Force	・Surge Voltage
・Operation　Duty Cycle	・Magnetic Short Circuit

Solenoid

A Solenoid is an electric magnet that converts electrical energy into mechanical energy. The movable armature (Plunger) is drawn and moves linearly by the magnetic pull force generated when a current (AC or DC) flows into a coil. Solenoids are used as actuators to control external parts utilizing plunger motions.

Keep Solenoid

Keep Solenoids are power-saving solenoids with permanent magnets installed inside of　the magnetic circuit. With a small pulse of electrical current, a plunger is attracted to a fixed core and latched magnetically in this position without constantly applying electrical current.

Stroke

Stroke is the distance a plunger travels from its starting position to where it is attracted to a fixed core.

Pull Force

Pull Force is the maximum load required for a plunger to be pulled when energized.

Holding Force

Holding Force is the maximum load required for a plunger to be held in the energized position.

Operation　Duty Cycle

Operation Duty Cycle is the rated cycle time (ON and OFF time) that a solenoid operates within a specified allowable temperature rise and other limitations when it is operating continuously, intermittently, or for a short period of time under a specified operating condition.

Magnetomotive force

Magnetomotive Force is the strength of a magnetic field in a coil of wire, which is expressed in units called “ampere-turns,” the product of electrical current flowing in a coil and turns of wire.
The larger the magnetomotive force, the larger the pull force.
It reaches its saturation point determined by the magnetic characteristics of each magnetic material.

Temperature Rise

When a current flows into a solenoid, the coil heats up as its coil resistance increases.
The coil temperature rises as time passes, but it saturates when the calorific value of coil and the heat emission value equal out.

Residual Magnetism or Residual Holding Force

One of the solenoid components is magnetic material (iron).
Due to the magnetic characteristics of the material, magnetism remains after cutting off the power.
This is called Residual Magnetism.
The holding force of the solenoid caused by residual magnetism is called Residual Holding Force.
When residual holding force is larger than a release load, the plunger won’t be released, causing a release operation failure.

Heat-resistant Classes (Insulation Classes)

Temperature of electrical products rises when energized, possibly resulting in damage when it exceeds the allowable temperature of an insulator.
Electrical products must be operated in such conditions where the maximum operation temperature of the products does not exceed its allowable temperature specified by the insulation class.

Heat resistant class of IEC60085/ JISC4003

Insulation Classes	Y	A	E	B	F	H	N	R	250
Temperature ℃	90	105	120	130	155	180	200	220	250

Surge Voltage

Solenoids utilize magnetism generated by applying a current to a coil. Cutting off this current, a reverse voltage is generated in attempting to maintain the magnetism that the coil generates.
This voltage is called Surge voltage, which requires an extra attention because it may cause damages to controlling circuits or switches.

Magnetic Short Circuit

Magnetism in a solenoid may leak, and a magnetic circuit may be generated outside of the solenoid if the solenoid mounting portion or the plunger jointing parts are composed of magnetic materials.
This is called Magnetic Short Circuit, lowering pull force or increasing residual holding force due to the residual magnetism of the magnetic parts.