Solenoid Valve Coil is the most important electronic control component in the solenoid valve. It is composed of copper or aluminum wire wound into a hollow form. It converts AC or DC electrical energy into linear mechanical motion to drive the solenoid valve.
This is achieved by placing a ferromagnetic core inside the coil. In the solenoid valve, the ferromagnetic core is called the valve core. When the current flows through the coil, due to the magnetic effect of the current, a magnetic field is generated in the surrounding space, thereby magnetizing the valve core into an electromagnet, and then under the electromagnetic force, the electromagnet further slide upward into the coil, thereby opening the valve port or pilot hole to realize the on-state of the solenoid valve.
Table of contents
2. Solenoid Coil Classification
5. How Does a Solenoid Valve Coil Work?
6. How Is the Solenoid Valve Coil Manufactured?
8. Critical Information for New Solenoid Valve Coil Development
Main Structure
The conventional structure of solenoid coil includes:
Enameled copper wire
Bobbin
Pin
Yoke
Encapsulation
In addition, according to the actual use, there will be a magnetizing guide ring, a bridge used for rectifying, etc.
1) Enameled copper wire
Copper conductor with a coat of insulating paint on its surface, which is the core material of solenoid coil. Solenoid coils used in valves are designed and tested for continuous service. They all meet the thermal endurance specifications according to IEC 216.
| Insulation class | Allowable Max. Temp. Rise ℃ | Allowable Max. Oper. Temp. ℃ |
|---|---|---|
| B | 90 | 130 |
| F | 115 | 155 |
| H | 140 | 180 |
| N | 160 | 200 |
| R | 180 | 220 |
| Remarks: This clause does not apply to pulsation operated coils | ||
2) Bobbin
The bobbin is the carrier of enameled wire winding. According to the temperature rise of the coil and the actual use environment, different bobbin materials are selected, such as PA66, PPS, PBT, PET, etc., and a few of them are thermosetting BMC and PT-310
3) Pin
The function of pin is to realize the electrical connection between the internal enameled wire and the external. Similar to the same function, there are pins, terminals, flying leads, etc. Pin material is generally brass, such as H59, H62, H65, of which H62 is the majority.
4) Yoke
It is used to gather the magnetic field lines from the N pole to the S pole, increase the magnetic field strength and minimize the magnetic leakage into the air. A reasonable support structure design is conducive to improving the magnetic field strength. Generally, there are two kinds of support materials: low carbon steel cold-rolled plate and electrical pure iron (DT4C).
5) Encapsulation
It is used to combine coil parts into a whole, which plays a role of waterproof and dustproof. The plastic covered materials include thermosetting plastics and thermoplastic plastics.
Thermoplastic: this kind of plastic is characterized by being soft with the increase of temperature, being molded and hard after cooling. This process can be repeated many times. The thermoplastic coil has good weather resistance and toughness. The most common material is PA66, followed by PA6
Thermosetting plastic: this kind of plastic is characterized by curing at a certain temperature, after a certain time of heating or adding curing agent. The solidified plastic is hard and insoluble in solvent, and cannot be softened by heating. If the temperature is too high, it will decompose. The thermosetting coil has high temperature resistance, small shrinkage and flat shape during injection molding. At present, all the thermosetting materials are BMC, but the content and formula of glass fiber are slightly different
Solenoid Coil Classification
| Classification Category | Type |
|---|---|
| Based on Shape and Design | Linear Solenoid |
| Rotary Solenoid | |
| Tubular Solenoid | |
| Based on Function | Push Type Solenoid |
| Pull Type Solenoid | |
| Dual Action Solenoid | |
| Based on Electrical Characteristics | DC Solenoids |
| AC Solenoids | |
| Pulse Solenoids | |
| Based on Power Rating | Low Power Solenoids |
| High Power Solenoids | |
| Based on Material | Iron Core Solenoid |
| Air Core Solenoid | |
| Based on Duty Cycle | Continuous Duty Solenoid |
| Intermittent Duty Solenoid | |
| Based on Mounting Style | Panel Mounted Solenoids |
| In-Line Solenoids | |
| Based on Application | Industrial Solenoids |
| Automotive Solenoids | |
| Medical Solenoids |
1. Based on Shape and Design
- Linear Solenoid: A solenoid that creates linear motion, often used in applications like valves and actuators.
- Rotary Solenoid: A solenoid that creates rotational motion, used in applications requiring mechanical rotation.
- Tubular Solenoid: A solenoid with a coil that forms a tube shape, offering higher force output, used in specialized applications.
2. Based on Function
- Push Type Solenoid: Designed to push or extend a plunger or armature when energized. Used in locking mechanisms, car door latches, or control systems.
- Pull Type Solenoid: Pulls an armature or plunger into the coil when energized. Used in relays, actuators, and industrial machines.
- Dual Action Solenoid: Combines both push and pull functions in one unit, often used in control systems where movement in both directions is needed.
3. Based on Electrical Characteristics
- DC Solenoids: Operates using direct current. Common in low-power applications like locks, relays, and small actuators.
- AC Solenoids: Operates using alternating current. Typically used in high-power applications like electric valves and large actuators.
- Pulse Solenoids: Works with pulse signals, suitable for applications requiring short bursts of energy or rapid cycling.
4. Based on Power Rating
- Low Power Solenoids: Operates at low voltages and currents, used in devices like locks and vending machines.
- High Power Solenoids: Designed for high-force and high-power input applications, such as industrial equipment and automotive starters.
5. Based on Material
- Iron Core Solenoid: Uses an iron core to increase the magnetic field strength, suitable for high-force or high-efficiency applications.
- Air Core Solenoid: Does not have a magnetic core, making it lighter and more efficient, typically used in low-force applications.
6. Based on Duty Cycle
- Continuous Duty Solenoid: Designed for continuous operation without overheating, suitable for long-term use.
- Intermittent Duty Solenoid: Operates for short periods and requires time to cool down, used for short bursts of energy.
7. Based on Mounting Style
- Panel Mounted Solenoids: Mounted on a panel or surface, typically used in control systems.
- In-Line Solenoids: Installed within a system, typically in a line of tubing or pipes, often used in fluid control systems.
8. Based on Application
- Industrial Solenoids: Used in large-scale industrial applications like robotics, automation, and manufacturing.
- Automotive Solenoids: Commonly found in automotive applications like starters, door locks, and control systems.
- Medical Solenoids: Found in medical devices, such as infusion pumps or safety functions in medical equipment.
Classification by application: Pneumatic industry; Hydraulic industry; Household electrical appliances; Textiles industry; Refrigeration industry; Automobile industry; Explosion protection industry, and so on.
Classification by manufacturing process: Thermosetting/Thermoplastic/Non encapsulation;
Solenoid Coil Performance
Degrees of Protection:
Degrees of protection provided by electrical enclosures (IP Code), According to standards EN 60529 and IEC 529
The code letters IP (Ingress Protection) followed by 2 characteristic numerals: e.g. IP65. The first figure indicates the degree of protection of the energized parts and internal moving parts against ingress of solid foreign objects. The second figure indicates the degree of protection against ingress of water with harmful effects.
The encapsulation coil can generally reach IP64 or IP65; Water-proof coil can reach IP67
Turns
Measured by coil turns meter, usually the turn's tolerance follows below standard
| Turns | Turn tolerance |
|---|---|
| 0～300 | 0 |
| 300～500 | ±3 Turns |
| 500～20000 | ±0.6% |
| 20000～60000 | ±1.5% |
Resistance
① unless otherwise specified, the coil resistance value is the resistance value at 20 ℃;
② When the standard resistance value is < 1000 Ω, the resistance tolerance range is ± 5%
When the standard resistance value is ≥ 1000 Ω, the resistance tolerance range is ± 7%
Standard resistance conversion formula when the ambient temperature is not at 20 ℃
R2=R1×(T2 234.5)÷(234.5 20)
T2：Current ambient temperature；
R1: Standard resistance at 20 ℃；
R2：Resistance at current temperature。
Insulation resistance:
The insulation resistance between the power terminal and the grounding terminal shall not be less than 100m Ω under the environment of temperature (15-35) ℃ and relative humidity not more than 85%
Voltage level of insulation resistance measuring instrument:
| Rated voltage U (V) | Voltage level of insulation resistance measuring instrument |
|---|---|
| U<60 | ≥250 |
| 60≤U<300 | ≥500 |
| 300≤U<600 | ≥1000 |
Grounding resistance:
Use resistance tester to measure the resistance between the grounding terminal and the yoke, and the resistance between the grounding terminal and the Yoke or the metal surface shall be less than 1 Ω.
Coil temperature rise:
① test according to JB / T 6378;
② the temperature rise of coil assembly and the maximum temperature obtained by temperature environment shall not exceed the following table.
Withstand voltage test:
Use the power frequency withstand voltage tester to apply the test voltage specified in the table below between the power supply terminal and the grounding terminal, set the leakage current to 1mA, apply the type test for 1min, apply the factory test for 1s (test voltage increases by 10%), and there shall be no breakdown, discharge or flashover.
Turn to turn withstand voltage test
Take one as the reference coil, and then take any one as the tested coil. Apply the impulse voltage wave specified in the following table between the two coil terminals or between the head and tail outgoing lines. The test time is 1-3s. Compare the difference between the two oscillation waveforms. The waveforms should be consistent, and the product difference is less than 20%.
| Rated voltage U (V) | Withstand voltage and Turn to turn withstand voltage test (v) |
|---|---|
| U<60 | ≥1000 |
| 60≤U<300 | ≥2000 |
| 300≤U<600 | ≥2500 |
Corrosion resistance:
Coil integral parts or corresponding metal parts shall be subject to continuous salt spray test for not less than 24 hours in accordance with GB / T 2423.17 or according to customer requirements (such as automobile products). After the test, the metal coating and coating surface shall be free of rust.
Appearance:
No defect such as scar, deformation, crack, bubble, etc.
Tension of power line:
the power line, coil shell and connecting terminal shall bear the following pressure without visible damage.
| Rated magnetic cross-sectional area mm² | AWG wire gauge | Tensile force | Rated magnetic cross-sectional area mm² | AWG wire gauge | Tensile force |
|---|---|---|---|---|---|
| N | N | ||||
| 0.08 | 28 | 8.9 | 0.75 | 18 | 89 |
| 0.13 | 26 | 13.4 | 1 | - | 104 |
| 0.2 | 24 | 22.3 | 1.5 | 16 | 134 |
| 0.34 | 22 | 35.6 | 2.5 | 14 | 223 |
| 0.5 | 20 | 57.9 | 4 | 12 | 312 |
How Does a Solenoid Valve Coil Work?
A solenoid valve coil operates by using an electric current to create a magnetic field that moves a metal armature, which controls the valve's position (open or closed). Here's how it works in a bit more detail:
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Magnetic Field Creation: When an electric current flows through the solenoid coil, it generates a magnetic field around the coil.
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Movement of the Armature: The magnetic field attracts or repels an armature (a movable metal piece) inside the valve, causing it to shift.
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Valve Action:
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Energized Coil: The armature moves to either open or close the valve, allowing or stopping the flow of liquid or gas.
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De-energized Coil: When the current is turned off, the armature returns to its resting position (due to a spring or gravity), either closing or opening the valve, depending on the type.
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-
Valve Types:
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Normally Open (NO): The valve is open when the coil is off and closes when the coil is energized.
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Normally Closed (NC): The valve is closed when the coil is off and opens when the coil is energized.
-
This design allows solenoid valves to control the flow of fluids or gases automatically, making them widely used in industrial, HVAC, and automation systems.
How Is the Solenoid Valve Coil Manufactured?
1. Wire Winding
Copper or enameled wire is tightly wound around a plastic or metal spool (bobbin) using a coil winding machine. The number of turns is carefully controlled to match the coil's electrical requirements.
2. Insulation
The wound coil is coated with insulation materials like varnish or epoxy resin to protect it from moisture, heat, and vibration.
3. Core Insertion
A magnetic core (usually made of iron or steel) is inserted into the coil to enhance its magnetic strength when powered.
4. Encapsulation
The coil is enclosed in a plastic or metal housing for protection, and electrical terminals or connectors are added for power supply.
5. Testing
Each coil is tested for electrical resistance, insulation, and magnetic performance to ensure quality and reliability.
This process ensures the coil can reliably control the solenoid valve in various applications.
FAQ
Why is it important?
The coil controls the valve's action, enabling automated flow control of liquids or gases.
What types are there?
Mainly normally closed (valve closed when off) and normally open (valve open when off).
How to choose the right coil?
Match voltage, duty cycle, and environment to ensure reliable operation and avoid damage.
Critical Information for New Solenoid Valve Coil Development
1. Working voltage
The frequency shall be provided for AC, and the power difference between 50Hz and 60Hz of the same coil is about 1.2 times, for example: 7.2W for 50Hz and 6.0w for 60Hz; 60Hz for 50Hz coil, and the voltage difference is about 1.095 times, for example, AC220V50HZ and AC240V 60Hz coil are universal)
2. Power or resistance
3. Armature's Diameter, or Coil's hole and aperture
4. Working environment: temperature, humidity, indoor or outdoor, protection, etc
5. Connection with external power supply: pin type/leading wire type/standard interface, etc.
6. Application
7. Other requirements: such as environmental protection material requirements or certification
Summary
In essence, the solenoid valve coil acts as the vital link between electrical control signals and the physical operation of valves. Its efficiency, durability, and responsiveness directly impact the overall system's effectiveness. Whether you're dealing with high-temperature environments, variable voltages, or demanding industrial cycles, selecting a coil that matches your specific application requirements is essential. If you're looking for solenoid valve coils that combine advanced materials, precision manufacturing, and proven reliability, we invite you to explore our product range. Our brand is committed to delivering innovative solutions tailored to your operational challenges, ensuring your systems run smoothly and efficiently.
