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Solenoid Valve Coil Tips

An apparatus for generating electromagnetic power. There are conductive winding match its power wounded around outside of coil, when energized the coil has a current with magnetic feature like a magnet, it also called solenoid coil (or electromagnet).
The shape of coil is mostly produced in rectangular to make the core more easily magnetized. Further, in order to demagnetize the solenoid when the electric power turned off immediately, degaussing faster material soft iron or silicon steel is often used, this solenoid with magnetic power when energized and no magnetic if de-energized. Solenoid coil (Electromagnet) has an extremely wide range of applications in industry, due to its invention also enables the generator power has been greatly improved. – finotek.com

Solenoid Valve Coil Structure:
The solenoid valve coil is composed of turns, power connector and iron housing.

The coil is usual covered by plastic materials through plastic injection machine. Some manufacturers are using technology of adding 30 % of glass fibers in plastic materials to increase coils’ rigidity. In order the turns generates a magnetic force to form a loop circuit, and receiving a smaller magnetic reluctance, the turns must have a considerable thickness of outer magnetic yoke and using  electric pure iron which requires good permeability , low residual magnetism.

Solenoid-Valve-Coil-Tips-interal-and-external-yoke

Internal magnetic yoke  |  External magnetic yoke

Internal magnetic yoke for coil feature:
Better magnetic properties, but because of different coefficient of thermal expansion for iron and plastics, a gap is easily generated while in the process of expansion and contraction.

External magnetic yoke for coil feature:
Better thermal performance and can protect the coil to reduce mechanical damage, but less safety and convenience than internal type for hydraulic field operation.

It is proportional to the current through the coil turns and turns of the electromagnetic force and numbers.  Thick copper wire, the number of turns increases, a large electromagnetic force will be able to obtain under same voltage and current, of course, the price will be higher for larger the volume of the valve coils.

Solenoid Coil AC-DC Power Supply:
Finotek is offering the solenoid valve coils in DC:12V, 24V and AC: 110 (115)V、220 (230)V to various customer requirements and customized voltage like DC: 6V, 20V,30V,72V is available. All of Finotek solenoid valve coils with same power at different voltage, same installation dimensions for interchangeable and replace to other brands.

Most cartridge valves are used in hydraulic mobile machinery, power supply comes from the battery first, often around 24V DC. But the voltage will be higher when the internal combustion engine -driven generator to charge the battery, some even more than 28V DC, but also may bring some AC current, which will be able take into consideration to solve trouble shooting while a solenoid valve coil broken.

Operating Temperature, Ambient Temperature & Insulation Class of Solenoid Coil:
When a solenoid coil works, in addition to the current adopted in just zero point zero seconds have power to push armature doing some mechanical action, the rest of the time all of its power convert to heat, therefore, the higher temperature is inevitable (Not to mention that solenoid valve coil can continue to work with100% working system).  

Solenoid-Valve-Coil-Tips-curve

t: Time ; T: Temperature ; F: Electromagnetic Force ; i: Electric Current ; P: Power ; U: Voltage

As the temperature difference between the coil and the environment is growing, more and more heat radiation.  To a certain temperature point, the heating and cooling keeps balance, therefore, the coil temperature is not rise any more.

The equilibrium temperature depends on the thermal conditions, on the one hand – the size of the coil surface area, heat transfer coefficient; the other hand, depending on the temperature of the surrounding environment.

Because the equilibrium temperature of continuous working coil easily reaches 100 ℃ while the solenoid valve is energized, therefore, the coil insulation rating of at least class F, that is the maximum temperature 155 ℃, also used the H level and N stage, the maximum temperature was 180 ℃ and 200 ℃. In view of the coil may reach very high temperatures, therefore, to consider the good protective measures to avoid contact with the coil and operating personnel due to burns.

Operating Voltage & Current:
There are valve coil standards, the voltage of coil should be allowed input voltage of ± 10% deviation.

But it should be noted, because the electromagnetic force is proportional to the current through the electromagnetic coil, and the resistance of the coil increases as the temperature rises, the operating current will decrease and leads to decline of the electromagnetic force. Therefore, to maintain the normal operation of the input voltage and ambient temperature within the coil working area shown in below.
coil-input-voltage-and-ambient-temperature

Slightly different for each valve coil manufacturer is not necessary to concern it. Conversely, insufficient voltage, the coil still can operate at lower ambient temperatures, but it can not work properly when the ambient temperature rises.

 

Reverse Voltage Surge Protection:
When the solenoid valve coil is energized, the current is gradually increasing due to inductance effects of coil. The coil inductance starts to increase while the movement of coil armature which will leads to a decline of the current through the coil in a short time, after the end of the armature stroke, the current is gradually increased again until reaching stable value.

When the coil is de-energized, the current was suddenly cut off, there is a high reverse voltage shock caused by the magnetic field change. The voltage at that value reaches 20 times more than rated voltage, it is likely to damage the coil insulation layer.
Pleas pay particular attention that the general electromagnetic coil is non-polar, but there is a polarity since with a diode inside. Wiring must be connected in accordance with the polarity given indication, otherwise, it will cause a short circuit current through the diode, burning the solenoid valve coil at last.

Failure causes and preventive measures:
Unlike mechanical movement, there is no wear and tear of electron motion. In theory, electromagnetic (solenoid) coil should be unlimited life. But in fact there is always the damage, but also as one of the main solenoid valve failure. The reasons are as follows:

1- Damaged by sudden appropriately impact.
2- If over tightened of coil fastening nut, it may resulting in tiny cracks at coil plastic layer.
3- Armature sleeve is corroded to expand, will damage the coil of plastic layer. So there are two O-rings often installed on the both side of coil to prevent water infiltration between the coil and sleeve.
4- The wire connection plug of ISO / DIN43650 is mostly used in hydraulic valves, but there is a small gap existing between the metal pins and plastic element. If the plug rubber seal is not installed properly or missing, water may enter into the coil inside through the small gap especially if the valve is used in the open-air environment.
5- The coil will generate heat when the valve is operation. Air will expand between turns and release from gaps of between the incoming line and plastic shell and other crevice. When solenoid valve not works and become cooling, the internal pressure is reduced, the air will be inhaled to the coil. This is called coil “breathing” phenomenon. This will allow water vapor into the coil can lead to corrosion. Some valve coil manufacturers began to use flat copper wire wound coils, in order to reduce the gap between the lines.
6- Due to corrosion and high temperature insulation aging, the coil wire of short circuit occurs between the turn circles. A small amount of short-circuiting between copper line, the solenoid can be able to still work. However, with the increase number of the short-circuit in the coil, the coil resistance is reduced, the current through the coil rises. Short-circuit between the line turns will lead abnormal heat at points, damage acceleration.

For all above cases, the best preventive measures: regular measuring the resistance of the coil. If the resistance of a coil decreased 15%~ 20 % than normal, it is certainly not for a long use anymore. Even if the machine can work, but it is better to replace it as early as possible. It should be noted that the resistance of the coil changes with temperature, this factor should be take into account while coil measurement.
More advanced programmable controller PLC can monitor the output current at each output port. If ambient temperature can be detected and with appropriate algorithms, the pre-alarm of coil damage can be achieved.

Coil Protection Standards:
Water, particularly impurities and Water chemical solvents is fatal factor to coils. Therefore, the standard of IEC144 and DIN40050-9 provides a waterproof and dustproof.
IP65: The protection class requirement is to prevent dust from entering and the coil can withstand the impact of a low pressure water jets from the outside in the 3m.

IP67: The protection class requirement is to prevent dust from entering and the coil can be immersed in deep water lm 30min without any damage.

IP69K: The protection class requirement is to prevent dust from entering, and the coil can withstand high pressure within a distance 10~15cm (10MPa) in high temperature (80℃) and impacted by mixed detergent water column.

Coil Connection type:
Solenoid-Valve-Coil-connection-type

1: DIN EN 175301(Standard for solenoid valve)coil ;  2: Metri-Pack solenoid coil ;  3: Solenoid coil with two leading line ;   4: Deutsch (DT04-4P) of solenoid coil ;  5: ISO/DIN43650  of solenoid coil ;  6: Solenoid coil lines with protected tube  

The solenoid coils for hydraulic valve are often equipped with ISO/DIN43650 connectors of protection class IP65, hence, there is a variety of other types of connectors (Plugs or wires) to meet different requirements especially for engineering machinery needs. The wire connector (Plug or wires) for coil listed below generally can reach class of IP67. However, users should note that to prevent water from entering the coil wire insulation sleeve and the gap between the metal lines.

2017-03-05T01:41:04+00:00

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