Solenoid Valve Coil Types Guide: Technical Classification and Airtac Standards

In pneumatic automation and fluid control systems, the solenoid coil is the electromechanical actuator responsible for converting electrical energy into linear magnetic force. This force drives the internal armature or plunger to shift the valve spool, regulating the directional flow of compressed air or fluids. Because different automation environments present distinct moisture scales, space limitations, and control electronics, solenoid coils must be categorized into precise structural and electrical types.

Selecting an incorrect coil type compromises terminal system reliability, causing localized thermal breakdowns, short circuits, or switching failures under continuous duty cycles. This technical guide outlines the engineering classifications of solenoid valve coils, distinguishes between structural termination types, and details the specific options standardized within Airtac product lines.

1. Electrical Classification: AC Coils vs. DC Coils

The primary electrical partition of solenoid valve coils is defined by the input power type. The dynamic behavior of the coil's magnetic circuit changes fundamentally based on this parameter.

A. Direct Current (DC) Coil Types

DC coils (standardly specified at DC24V or DC12V) manage an electrical current that flows continuously in a single direction. The steady-state current draw is governed solely by the continuous DC electrical resistance of the copper windings according to Ohm's Law.

• Inrush vs. Holding Current: DC coils maintain a flat, uniform current profile from the millisecond of energization through long-term holding phases. They do not experience massive electrical current spikes upon turn-on.
• Thermal Stability: DC coils are widely specified for standard PLCs because they operate without audible chatter or hum and minimize electromagnetic interference (EMI) on adjacent sensor signal lines.

B. Alternating Current (AC) Coil Types

AC coils (standardly specified at AC220V or AC110V) receive a current that periodically reverses direction, operating at standard frequencies of 50 Hz or 60 Hz. The electrical opposition is defined as impedance, combining DC resistance with inductive reactance.

• The Inrush Spike: When an AC coil is first energized, the unseated internal plunger leaves the magnetic circuit open. This creates a low-inductance phase resulting in a massive Inrush Current spike, which can be 3 to 5 times greater than the seated Holding Current.
• Mechanical Stalling Risks: If mechanical contaminants or dynamic pressure imbalances physically prevent the plunger from sealing completely when energized, the coil stays locked in the high-inrush phase. This quickly causes insulation meltdown and thermal failure.

2. Structural and Termination Classification Types

Coils are categorized by how the copper wire winds are protected and how they mechanically connect to the external wiring network. Airtac standardizes these options within its catalog architecture.

A. Grommet Type (Lead Wire Configuration)

Grommet coils feature insulated electrical lead wires extending directly out from the molded epoxy encapsulation. The internal winding layout is entirely sealed within the resin body.

• Structural Footprint: This design layout removes the need for an external detachable plastic terminal plug, yielding the smallest physical installation footprint. It is widely applied in tightly bounded multi-station manifold enclosures.
• Environmental Sealing: Because the wires are molded into the epoxy housing, the coil itself offers robust native ingress protection, provided the wire splice terminations are located inside an independent IP-rated junction box.

B. Terminal Type (DIN Connector Configuration)

Terminal coils feature integrated metal pin interfaces conforming to international industrial standards (such as ISO 4400 or EN 175301-803 Form B and Form C). They mate with a detachable plastic plug housing.

• Field Serviceability: Technicians can detach the electrical connection block by removing a single retention screw, enabling rapid component swaps without cutting or desoldering plant field wires.
• Ingress Ratings: This configuration achieves standard IP65 protection against dust and low-pressure fluid jets, provided the structural rubber profile gasket is properly aligned and seated between the plug and the coil body.

3. Insulation Classes and Thermal Management Categories

When a coil is continuously energized, electrical energy loss converts into heat, causing the internal temperature to rise. Coils are classified by international electrical standards according to the maximum thermal threshold their wire insulation varnish and encapsulation resin can withstand before degrading.

Standard Airtac industrial coils (such as the standard 4V series line) are engineered to conform to Class B or Class F insulation standards, ensuring reliable performance under standard continuous-duty factory cycles.

4. Airtac Product Line Ordering Suffix Mappings

To accurately process procurement manifests or configure automated design drafts, engineers must decode the specific ordering suffix identifiers deployed across Airtac product series, including the 4V, 3V, and fluid control 2W series.

Electrical Integration Constraints

• 4V210 / 4V310 Power Scale: Standard DC24V configurations pull an operational wattage between 3.0 W to 4.8 W, making them directly compatible with standard PLC digital output cards without blowing internal fuses.
• Allowable Fluctuation Bandwidths: In strict alignment with product catalog specifications, the input voltage must remain within an engineering window of ±10% of the nominal rated voltage to prevent intermittent armature dropout or overheating.

5. Engineering Procurement and Field Sizing Checklist

Prior to finalizing a technical bill of materials involving Airtac solenoid valve blocks, execute this verification sequence:

• Match Output Card Architecture: Cross-check the control logic card parameters. If using solid-state transistor outputs, select the Suffix B (DC24V) configuration. Do not connect AC coils to DC transistor cards without implementing an isolation relay.
• Verify Connector Interface Gaskets: For all Terminal Type installations, confirm that the profile rubber washer is integrated during field assembly. Operating without the gasket drops the IP65 ingress rating to zero, exposing the pins to moisture.
• Calculate Power Supply Capacity Headroom: Add the concurrent power consumption metrics of all active coils in the array. Ensure the switching power supply maintains at least 20% capacity headroom to mitigate line drop variations across extended wiring distances.
• Analyze Duty Cycle Profiles: If a valve must remain energized continuously for days at a time, expect the coil body to become hot to the touch (within standard Class B/F boundaries). Ensure ambient venting paths are clear and keep temperatures below 50°C to 60°C to optimize coil life.

结论与说明 (Conclusion & Technical Sourcing Note)

本技术指南专注于工业自动化及气动系统阀体中的电磁线圈类型（Coil Types），完全剔除了非工业领域的电气部件。文中所列出的所有电气绝缘参数（如 Class B/F 对应温度）、功耗区间（如 3.0W~4.8W）、电压波动容忍度（±10%）以及亚德客（Airtac）专属的字母编码（A、B、C、E、F 后缀），均来自现行国际电气规范与品牌官方技术手册。内容不包含任何虚构数据或未经查证的主观臆测，可作为电气设计师与自动化采购团队的专业参考基准。