TL;DR: AC laminated solenoids stack thin silicon-steel sheets in place of a solid core to stop eddy currents from heating the frame on 50/60Hz supplies. When specifying one, check three things beyond force and stroke: inrush current, which peaks at full stroke, so fuses, contacts, and transformers must be rated for starting current rather than seated current; seating, since a plunger that cannot fully seat hums and overheats the coil; and whether the job would run better on DC through a rectifier. Shih Shin’s SH-AS series spans 10mm to 30mm strokes and 0.5kg to 5kg rated force, all on 110/220V AC, 50/60Hz.
Purchasing engineers usually meet laminated solenoids in one of two situations: a machine builder needs a line-voltage actuator for a valve, latch, or feeder, or a buyer has a failed unit in hand and a production line waiting. Either way, the datasheet answers only half the questions. This guide covers the other half: what the lamination actually does, why inrush current dominates AC coil behavior, where hum comes from, and how to turn an application into a clean spec. Examples use Shih Shin’s SH-AS series, an AC laminated frame line rated for 110/220V AC at 50/60Hz and applied in linkage systems, valve actuators, counting devices, brake systems, and feed hoppers.
Why the Core Is Laminated
Feed alternating current to a coil wrapped around a solid iron core and the core behaves like the shorted secondary of a transformer. Flux reverses at line frequency, and each reversal induces circulating currents, called eddy currents, in the body of the iron. Those currents do no mechanical work. They heat the core, waste input power, and blunt the flux change that produces pull.
A laminated core interrupts those current loops. The frame and plunger are stacked from thin silicon-steel sheets, each with an insulating surface layer, oriented so the sheet plane runs parallel to the flux path. Eddy currents can no longer circulate through the full cross-section; they are confined within each thin sheet, where path resistance is high and losses fall sharply. The silicon content raises the steel’s resistivity and cuts losses further.
For a buyer, this construction has three practical consequences. First, a laminated frame runs far cooler on AC than any solid-core part could. Second, the reverse also holds: a DC solenoid with a solid core overheats quickly on an AC supply, so AC and DC units are not interchangeable even when the mounting pattern looks similar. Third, the lamination stack produces the rectangular frame geometry you see in the dimension columns of an AC datasheet, which decides how the unit packages into your machine.
Inrush Current Decides Your Electrical Design
An AC solenoid draws its highest current at switch-on, when the plunger sits at full stroke and the magnetic circuit contains a large air gap. The gap keeps inductance low, so coil impedance is low and the line drives a high current through the winding. As the plunger travels in and the gap closes, inductance climbs, impedance climbs with it, and current falls to a much lower seated value.
That behavior drives four specification decisions:
- Protection. Fuses and breakers must ride through the inrush without nuisance tripping. Select time-delay types and size them against starting current, not seated current.
- Supply capacity. Control transformers and switching contacts see the inrush on every machine cycle. Rate them for current at full stroke.
- Stroke discipline. The longer the stroke you specify, the larger the starting gap and the higher and longer the inrush phase. Choose the shortest stroke that completes the mechanical job; extra travel margin costs you coil heat.
- Stall behavior. If the load jams and the plunger cannot seat, current never falls from the inrush level and the coil overheats. Apply AC laminated solenoids so the plunger always completes its stroke.
SH-AS coils are specified for 110/220V AC at 50/60Hz. Confirm the coil voltage against your line before ordering, and verify it again at incoming inspection.
Hum and Chatter: Mechanical Causes, Mechanical Fixes
AC pull force is not constant. It pulsates at twice the line frequency and passes close to zero on every half cycle. A copper shading ring set into the pole face carries an induced current that delays part of the flux, so net force never quite reaches zero and the seated plunger stays put. When a solenoid buzzes or chatters, something is defeating that arrangement:
- Incomplete seating. Dirt, chips, or burrs on the pole faces hold the plunger slightly off its seat, which keeps current high and lets the force pulsation shake the stack.
- Side load. A load pulling off the stroke axis drags the plunger against its guide, slows seating, and invites chatter. Align the linkage so force acts along the plunger centerline.
- Low voltage at the coil. Undervoltage weakens pull-in and can leave the plunger hovering short of seat. Measure at the coil terminals under load, not at the panel.
- Damaged shading ring. A cracked ring removes the anti-chatter mechanism entirely and produces a loud, continuous buzz. This one calls for replacement, not adjustment.
Mounting matters too. Bolt the frame to a stiff surface; a resonant bracket amplifies residual vibration into audible noise that gets blamed on the solenoid.
Reading the SH-AS Datasheet
The table below lists six representative models spanning the series. All operate on 110/220V AC, 50/60Hz.
| Model | Stroke | Rated force | Dimensions (mm) | Plunger weight | Total weight |
|---|---|---|---|---|---|
| SH-AS05 | 10mm | 0.5kg | 84 x 33 x 38 | 62g | 0.2kg |
| SH-AS08 | 10mm | 0.8kg | 84 x 27 x 38 | 95g | 0.3kg |
| SH-AS10 | 15mm | 1.5kg | 93 x 53 x 50 | 138g | 0.45kg |
| SH-AS15 | 15mm | 2kg | 93 x 57 x 50 | 153g | 0.5kg |
| SH-AS25 | 20mm | 4kg | 130 x 75 x 63 | 348g | 1.3kg |
| SH-AS35 | 30mm | 5kg | 170 x 90 x 86 | 598g | 2.3kg |
Source: SH-AS series datasheet, Shih Shin Technology. Values are for reference and subject to design revision.
Three reading notes. First, pair each force value with its listed stroke: the SH-AS10 line means 1.5kg of pull across a 15mm stroke, and the load at the start of travel, where the air gap is largest, is the case to check. Second, the plunger weight column is your moving mass. It sets impact energy at seating and matters when the solenoid cycles fast or drives a light mechanism; the 62g plunger of the SH-AS05 and the 598g plunger of the SH-AS35 are different mechanical problems. Third, frame size and force do not track perfectly. The compact SH-ASS20 delivers 3.5kg over a 20mm stroke from a 116 x 65 x 55 frame at 0.8kg total weight, while the larger SH-AS20 delivers 3kg from a 130 x 70 x 63 frame at 1.15kg. When mounting space is tight, ask about compact variants before jumping to the next frame size.
The full series, together with DC frame, tubular, and holding types, is listed in the industrial solenoid product range.
AC Laminated or DC with a Rectifier?
Some machine builders run DC solenoids from the AC line through a bridge rectifier, and for certain jobs that is the right call. The choice usually comes down to four factors:
- Actuation character. The AC inrush delivers a strong initial pull that snaps loads home. DC current builds through the coil inductance, so pull develops more gradually.
- Noise. DC force is steady, so a DC unit runs quiet. If the actuator sits near an operator, that alone can settle the question.
- Stall tolerance. A stalled DC coil draws its normal resistance-limited current and survives longer. A stalled AC coil sits at inrush current and cooks. Jam-prone mechanisms favor DC.
- Parts count. AC laminated units connect straight to the line with no rectifier or supply, which keeps panel wiring short and the BOM simple.
A workable default: specify AC laminated when you need line-voltage operation and fast actuation, and the mechanism reliably lets the plunger seat. Move to DC when audible noise or jam tolerance dominates the requirement.
How to Specify: What to Put in Your RFQ
An inquiry that includes the following points gets a usable answer in one round instead of three:
- Required force at the start of stroke, with your margin stated
- Shortest stroke that completes the motion
- Line voltage and frequency
- Duty cycle: energized time, off time, and cycles per minute
- Ambient temperature at the mounting point
- Available mounting envelope, in millimeters
- How the load couples to the plunger, and whether side load is possible
If you are replacing an installed unit and the nameplate is gone or unreadable, the solenoid cross-reference page explains what to measure and photograph so an equivalent can be identified.
Specification values quoted in this guide are transcribed from factory datasheets under the site’s editorial process: no interpolated or estimated figures.
For a quotation, or an engineering opinion on a marginal application, email info@solenoids.com.tw with the checklist above. The engineering team normally replies within 24 to 48 hours on business days.
Frequently Asked Questions
Our new AC solenoid buzzes loudly on the machine. Did we get a bad unit?
Usually the unit is fine and something is stopping the plunger from seating fully. Check for chips or burrs on the pole faces, side load from a misaligned linkage, and low voltage measured at the coil terminals under load. A cracked shading ring also causes a loud continuous buzz and does require replacement. If the buzz persists after these checks, send the symptoms and your supply details to the manufacturer for review.
What happens if the plunger jams and the solenoid can't finish its stroke?
The coil keeps drawing current near the inrush level instead of dropping to the seated value, and it overheats quickly. Design the mechanism so the plunger always completes its stroke, put travel stops on the load rather than the solenoid, and treat any jam-prone application as a candidate for DC operation or a design review before release.
