{"id":2875,"date":"2026-05-19T01:00:00","date_gmt":"2026-05-19T01:00:00","guid":{"rendered":"https:\/\/shieldhz.com\/?p=2875"},"modified":"2026-05-10T06:29:50","modified_gmt":"2026-05-10T06:29:50","slug":"lw28-vs-lw42-rotary-cam-switch","status":"publish","type":"post","link":"https:\/\/shieldhz.com\/ar\/lw28-vs-lw42-rotary-cam-switch\/","title":{"rendered":"LW28 \u0645\u0642\u0627\u0628\u0644 LW42 \u0645\u0641\u062a\u0627\u062d \u0643\u0627\u0645\u064a\u0631\u0627 \u062f\u0648\u0627\u0631\u0629: \u0645\u0627 \u0647\u064a \u0627\u0644\u0633\u0644\u0633\u0644\u0629 \u0627\u0644\u062a\u064a \u062a\u0646\u0627\u0633\u0628 \u0644\u0648\u062d\u062a\u0643"},"content":{"rendered":"

Choosing between the LW28 and LW42 rotary cam switch is not a simple smaller-current versus larger-current decision. Shieldhz current product information positions LW28 as a broad 10A to 315A IEC 60947-3 rotary cam switch family for motor control, source changeover, metering, and custom cam programs. LW42 is a compact changeover route for 20A, 25A, and 32A applications where panel space, handle format, AC-23A\/AC-3 data, and mounting options matter. Select by exact part-number datasheet, contact chart, mounting drawing, and utilization category.<\/p>\n

LW28 vs LW42 at a Glance: Core Differences That Drive the Choice<\/h2>\n

The LW28 and LW42 share the same cam-operated contact principle and both fall under the scope of IEC 60947-3:2020+AMD1:2025<\/a>, which applies to switches, disconnectors, switch-disconnectors, and fuse-combination units for distribution and motor circuits with rated voltage up to 1000V AC or 1500V DC. Beyond that shared foundation, the two series diverge in ways that matter at the panel-design stage.<\/p>\n

The LW28 and LW42 share the same cam-operated contact principle, but they serve different specification routes. LW28 covers a broad range of rotary cam switch configurations, including motor control, metering, and custom cam programs. LW42 is positioned as a compact changeover family with 20A, 25A, and 32A application routes. Do not infer duty from the series name alone; use the current Shieldhz datasheet to confirm rated operational current, utilization category, contact program, and mounting dimensions.<\/p>\n

\"LW28
Figure 1. Core concept behind LW28 vs LW42 rotary cam switch selection.<\/figcaption><\/figure>\n

Technical Specifications Compared: Ratings, Poles, and Contact Configurations<\/h2>\n

The table below gives engineers the parameter values needed to match each series to a circuit design. Values marked as datasheet-dependent should be confirmed against the current Shieldhz product datasheet before finalizing a specification.<\/p>\n

LW28 vs LW42 Core Ratings<\/h3>\n\n\n\n\n\n\n\n\n
Mounting Check<\/th>\nLW28 Series<\/th>\nLW42 Series<\/th>\n<\/tr>\n<\/thead>\n
Panel cutout<\/td>\nConfirm on the selected model drawing<\/td>\nConfirm on the selected model drawing<\/td>\n<\/tr>\n
Front bezel and handle clearance<\/td>\nFrame-specific<\/td>\nFrame-specific<\/td>\n<\/tr>\n
Rear pole-stack depth<\/td>\nConfirm with datasheet before drilling<\/td>\nConfirm with datasheet before drilling<\/td>\n<\/tr>\n
Interchangeability<\/td>\nDo not assume interchangeability across series<\/td>\nDo not assume interchangeability across series<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The utilization category distinction is the most consequential specification in this table. AC-23A, assigned to the LW42, requires the switch to make and break motor inrush currents — typically 6 to 10 times rated current — without contact welding or excessive arc erosion. A switch specified at AC-21A will not reliably break inductive motor loads that require AC-23A duty, even if the continuous current rating appears adequate on paper.<\/p>\n

For panels where pole count flexibility matters as much as current rating, the LW42’s range up to 12 poles allows a single switch to control multiple isolated circuit paths simultaneously, reducing component count in complex switching applications. The LW28 remains the more practical choice when the circuit topology is simpler and the 20A rating is sufficient.<\/p>\n

Specifying Utilization Categories in Practice<\/h3>\n

When the load type is mixed — for example, resistive instrumentation circuits alongside contactor coils on the same switch — apply the most demanding utilization category to the whole switch, not just the heaviest individual circuit. For motor selector applications, request the manufacturer’s contact chart and verify that the cam profile closes the correct pole pairs at each position before wiring. If the application sits at the boundary of two categories, size up. The cost difference between LW28 and LW42 is small compared to a contact-weld failure on a live feeder.<\/p>\n

Panel Space and Mounting: Where Each Series Physically Fits<\/h2>\n

Current rating and pole count narrow the choice to one series in most cases, but panel geometry often makes the final call — particularly in retrofit projects where the enclosure is already fixed.<\/p>\n

Dimensional Comparison<\/h3>\n\n\n\n\n\n\n\n\n
Parameter<\/th>\nLW28 Series<\/th>\nLW42 Series<\/th>\n<\/tr>\n<\/thead>\n
Panel cutout diameter<\/td>\n22mm<\/td>\n30mm<\/td>\n<\/tr>\n
Front bezel diameter<\/td>\nApprox. 40mm<\/td>\nApprox. 52mm<\/td>\n<\/tr>\n
Minimum panel thickness<\/td>\n1.5mm<\/td>\n2.0mm<\/td>\n<\/tr>\n
Pole stack depth (behind panel)<\/td>\nConfirm with datasheet<\/td>\nConfirm with datasheet<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The behind-panel depth is the dimension engineers most often underestimate. In compact DIN-rail enclosures or shallow wall-mount cabinets, the LW42’s deeper pole stack can conflict with cable trays or terminal blocks mounted directly behind the switch position. Confirm the rear projection dimension from the current Shieldhz datasheet before committing to a panel layout.<\/p>\n

Mounting Density Considerations<\/h3>\n

Because the LW28 shares the 22mm footprint with standard push button switches and indicator lights, it integrates cleanly into panels already laid out on a 22mm grid — typically with 30 to 40mm center-to-center spacing between devices. The LW42’s larger bezel requires at least 50mm center-to-center clearance to avoid overlap, which reduces the number of controls that fit across a standard 600mm panel width.<\/p>\n

For panel builders working with the LW28 series in environments exposed to moisture or wash-down conditions, confirm the IP rating of the specific variant ordered and verify enclosure compatibility with your installation standard. The LW42 series suits applications where the larger actuator diameter improves operator ergonomics or where the heavier contact assembly demands a more rigid panel mounting interface.<\/p>\n

\"LW28
Figure 2. Selection checks should connect the load, switching sequence, enclosure, and documentation requirements.<\/figcaption><\/figure>\n

Real-World Application Scenarios: Matching the Series to the Job<\/h2>\n

Dimensional constraints and ratings only tell part of the story. Seeing how each series performs in actual panel-build conditions makes the selection logic concrete.<\/p>\n

Scenario 1: Compact Machine Control Panel (LW28)<\/h3>\n

A panel builder assembling a conveyor drive enclosure with a 200mm x 300mm door cutout budget needs a multi-position selector switch for a 10A motor circuit at 380V AC. The LW28 rotary cam switch<\/a> fits this application directly: its 22mm mounting diameter keeps the door cutout small, and its rated insulation voltage of 690V AC covers the circuit comfortably. The compact cam stack also allows two or three switches to be mounted side-by-side without violating minimum spacing requirements.<\/p>\n

Scenario 2: Heavy-Duty Transfer Switch in a Distribution Board (LW42)<\/h3>\n

For a 63A, 690V AC transfer switching application — such as a generator changeover panel in a commercial building — the LW42 rotary cam switch<\/a> is the appropriate choice. Its 42mm body accommodates heavier contact bridges rated for AC-23A utilization category loads, where making and breaking inductive currents at full rated amperage is a routine operating condition. The larger cam geometry also provides more positive detent feel at each switching position, reducing operator error during manual changeover sequences.<\/p>\n

Scenario 3: Multi-Function Test Panel with Mixed Circuits (LW28 + LW42)<\/h3>\n

In a test bench panel combining low-current instrumentation circuits at or below 16A alongside a 40A main isolator, panel builders commonly use both series on the same DIN rail row. The LW28 handles the instrumentation selector positions while the LW42 manages the main circuit isolation. This mixed approach — consistent with IEC 60947-3:2020+AMD1:2025 guidance on matching switch ratings to individual circuit utilization categories — avoids over-specifying smaller circuits while ensuring the main isolator meets its breaking capacity requirement.<\/p>\n

\"LW28
Figure 3. Application wiring context should be verified against the manufacturer contact chart before energizing.<\/figcaption><\/figure>\n

Wiring Diagrams: How LW28 and LW42 Connect Differently in a Panel<\/h2>\n

Application scenarios confirm which series belongs in a given panel. The wiring approach then determines whether it performs correctly once installed.<\/p>\n

LW28 Control Circuit Wiring<\/h3>\n

The LW28 series is commonly wired into control circuits handling signals up to 10A at 380V AC. Its terminal numbering follows a sequential convention: terminals 1 and 2 form the first contact pair, 3 and 4 the second, and so on through up to 12 terminals depending on the pole configuration. In a typical motor selector application, the cam switch sits between the PLC output and the contactor coil, with the common feed entering terminal 1 and switched outputs leaving terminals 3, 5, and 7 for positions 1, 2, and 3 respectively.<\/p>\n

Because LW28 contact bridges are rated for resistive loads under utilization category AC-21A, the control circuit wiring must account for inductive derating when driving contactor coils. As a general guideline, reduce the switching current to 60 to 70 percent of the resistive rating for inductive loads, but confirm the exact derating factor from the Shieldhz datasheet for the specific variant ordered.<\/p>\n

LW42 Main Circuit Wiring<\/h3>\n

The LW42 series is designed for main circuit switching at up to 63A, with terminals arranged in paired rows — L1\/T1, L2\/T2, L3\/T3 — on the upper and lower faces of the switch body. This mirrored layout allows direct in-line insertion into a three-phase feeder without additional bus bridging. Terminal torque specifications for M4 screws should be confirmed from the current datasheet; under-torqued connections on 63A circuits generate enough heat to degrade the terminal block within months of commissioning.<\/p>\n

In a reversing starter panel, the LW42 cam switch connects upstream of two contactors, with its position contacts directing phase sequencing. The cam disc profile determines which terminal pairs close at each rotational step, so the wiring diagram must reference the manufacturer’s contact chart — available through the rotary cam switch product library<\/a> — to confirm open and closed states at each position before energizing.<\/p>\n

Wiring and Commissioning Tips from the Field<\/h3>\n

Always verify the cam contact chart against your wiring diagram before energizing. Cam disc profiles vary by position count, and an incorrect assumption about which poles close at position 0 is a common source of commissioning faults. On LW42 installations, torque terminal screws to the datasheet-specified value using a calibrated torque screwdriver. For LW28 control circuits driving contactor coils, add a snubber or RC suppressor across the coil terminals to reduce inductive kick — this extends contact life significantly in high-cycle applications. Label each switch position on the panel face with a legend plate before commissioning; rotary cam switches with more than three positions are a frequent source of operator error during manual changeover.<\/p>\n

Failure Modes and Maintenance: What Goes Wrong and How to Catch It Early<\/h2>\n

Correct wiring eliminates installation faults, but long-term reliability depends on understanding how each series degrades in service and what to inspect before a failure becomes a shutdown.<\/p>\n

Common Failure Modes by Series<\/h3>\n

The LW28 family spans multiple ratings and is often deployed where the selected cam program and utilization category match the circuit; contact oxidation and mechanical wear from frequent switching remain key inspection points. In motor control panels where the switch cycles dozens of times per shift, silver contact surfaces can develop oxidation, pitting, or contamination that raises contact resistance above the commissioning baseline or manufacturer acceptance threshold, causing localized heating and intermittent circuit behavior.<\/p>\n

The LW42 should be specified from its available compact current frames and utilization-category data; inductive loads still require careful confirmation because arc energy at each switching event is higher than in signal or metering duty. The dominant failure mode is contact erosion: repeated arcing gradually reduces contact mass, eventually causing incomplete circuit closure or welding under fault conditions. IEC 60947-3:2020+AMD1:2025 governs the making and breaking capacity requirements that both series must meet, and contact erosion is the primary reason rated mechanical endurance should be treated as a replacement trigger, not just a specification footnote. Confirm the endurance rating for your specific variant from the Shieldhz datasheet.<\/p>\n

Maintenance Checklist<\/h3>\n

Use this checklist during scheduled panel inspections, recommended at least every six months in industrial environments with moderate cycle rates. High-cycle applications warrant quarterly checks.<\/p>\n