Resistance
Voltage/Wattage (in operation, the coil resistance will increase due to the heating of the coil wire).
Residual Magnetism
The magnetism which remains in effect on a piece of magnetic material or between two pieces of magnetic material after the electromagnetic field created by the coil has been removed. An air gap is usually maintained between two magnetic poles to minimize the effects of residual magnetism.
Relative Permeability
The ratio of the flux density in a given medium to that which would be produced in a vacuum with the same magnetizing force. Non-magnetic materials, including air, have a relative permeability of 1, while magnetic materials such as iron, have initial relative permeabilities of approximately 2,000.
Rectifier
An electrical device for transforming alternating current into direct current.
Random Wound Coil
A coil whose turns are allowed to wind randomly in no specific pattern. One turn may overlap another or may lay side by side or even spiral completely across the surface of the coil. Normally carries a ±10% tolerance on resistance.
Pulse Width Modulation (PWM)
If a solenoid is controlled by a transistor which is signaled from a microprocessor, the PWM can be considered as an alternate means for reducing sizes or saving energy. PWM reduces the effective voltage by pulsing the voltage input. For example, if a solenoid has 12 volts supplied, but at 500 Hz at a 50%
Push Force
When energized, the push rod extends, pushing the load. A push solenoid is actually a pull solenoid with the addition of a push rod that rides against the internal face of the plunger extending through the fixed-pole piece.
Pulse Duty
An intermittent duty unit with extremely short ON time. A duty cycle is normally in the 10% to 25% range. This is maximum input power for that size solenoid.
Pull Force
When energized, the plunger retracts, pulling the load. De-energized, the plunger is extended to specified stroke distance.
Potted Coil
A common option for extended environmental protection is a potted or encapsulated coil. Potting or over-molding helps in making the coil humidity/splash resistant (in applications where this is common). If more severe conditions exist, further sealing of the coil cavity may be required.
