Component Snapshot At-a-Glance

• Model: VAJX11BP5243BA
• Alt. P/N: VAJX11DP5243BA (low-burden coil variant, different DC draw); VAJX13 (mechanical hand-reset latch version); MVAJ series (Midos draw-out rack form factor, incompatible base)
• Product Series: VAJX compact plug-in auxiliary relay family, standard panel flush mount, separate from Midos draw-out relay lineup
• Hardware Type: Fixed panel mount attracted armature electromechanical auxiliary relay, transparent front inspection cover, screw terminal wiring
• Key Feature: BP medium burden 110/125VDC control coil, self-reset operation, multiple silver alloy changeover contact stacks for multi-circuit logic expansion
• Primary Field Use: Expand protection relay contact count, route trip permissive signals, drive panel alarm lamps and remote SCADA discrete fault inputs.

Hard-Numbers: Technical Specifications

• Protocol Support: Pure electromechanical hardware, no digital bus communication; volt-free dry changeover contact outputs
• Port Count: DC coil supply terminals, multi-pole independent contact terminal sets for alarm, interlock and indication circuits
• Baud/Data Rate: No serial data transmission
• Operating Temperature: -10°C to +55°C cabinet operational; -40°C to +85°C storage
• Isolation Rating: 2000Vrms dielectric withstand between coil winding and contact wiring
• Power Draw: Medium burden BP coil, balanced DC load distribution on densely packed multi-relay panels
• Nominal Coil Voltage: 110/125 VDC station control battery
• Reset Method: Electrical self-reset; contacts return to normal state once coil de-energizes
• Operate Speed: ≤12ms full armature pull-in at rated DC voltage
• Contact Continuous Rating: 5A @300VDC resistive load; 40W DC inductive breaking capacity
• 3s Fault Make/Carry Rating: 30A peak for transient trip coil switching
• Physical Weight: 0.3kg fully assembled compact unit

The Real-World Problem It Solves

Single-contact protection relays lack enough output paths to feed local panel alarms, breaker interlocks and remote SCADA at the same time. Running multiple small signal relays adds dozens of wiring splices that vibrate open after years of plant cycling.Hand-reset VAJX13 units require on-site personnel to manually clear latched fault signals; remote control rooms cannot reset indication logic without sending a technician to the cabinet.Low-burden VAJX11DP coils create uneven DC bus loading across packed protection panels. Simultaneous multi-feeder faults trigger localized voltage sag and intermittent relay dropout.Midos MVAJ draw-out relays occupy wider rack slots and require dedicated CT shorting bases; compact VAJX11 fits standard panel cutouts for simple retrofit without cabinet layout rework.Where you’ll typically find it:

• Fossil power plant station service auxiliary breaker control and alarm panels
• Refinery MV motor MCC permissive interlock and fault indication logic cabinets
• Urban distribution substation ring main unit secondary SCADA signal routing panelsThis compact panel-mount auxiliary relay delivers multi-circuit contact expansion and self-reset operation without extra rack width or complex CT rack base hardware.

Hardware Architecture & Under-the-Hood Logic

This unit uses a lightweight attracted armature electromagnetic coil with no mechanical latching mechanism, no onboard microprocessor or signal sampling ICs. It is designed for fixed panel mounting, not Midos withdrawable rack bases.

1. Protection fault or permissive logic contact energizes the BP medium burden DC coil; magnetic flux pulls armature closed to switch all contact stacks simultaneously.
2. Once coil de-energizes, spring tension resets all contacts to normal state automatically, no manual front-panel reset required.
3. Medium-wattage BP coil balances total DC load draw on station battery, preventing uneven voltage sag across multi-relay panels during concurrent fault events.
4. Silver alloy contact tips resist arc erosion from frequent inductive DC switching, extending service life in high-cycle substation environments.
5. Front transparent cover exposes internal armature and contact stack for quick visual inspection without full terminal disconnection.
6. Rear screw terminal block supports standard 1.5–2.5mm² control wiring, no special crimp terminals required for field installation.

Field Service Pitfalls: What Rookies Get Wrong

Swapping VAJX11DP Low-Burden Coil Variant For VAJX11BP Medium-Burden Unit

New technicians pull VAJX11DP spare stock without matching model suffix. During multi-feeder simultaneous faults, uneven DC load creates localized bus sag; low-burden coils dropout prematurely, fault and permissive signals fail to transfer to SCADA and breaker interlocks.Field Rule: VAJX11BP medium-burden variant mandatory for dense multi-relay protection panels; segregate BP and DP coil VAJX11 spares in clearly labeled storage bins.

Mounting VAJX11 Into Midos Draw-out Relay Rack Base

Apprentices attempt to slot VAJX11 compact panel relay into Midos MVAJ rack chassis. Mismatched mechanical dimensions leave loose fit, terminal wiring stretches and vibrates open during plant load swings.Quick Fix: VAJX11 is fixed flush panel mount only; use MVAJ series if withdrawable CT-safe rack base installation is required.

Over-Torquing Rear Screw Terminals During Rewiring

Maintenance crews over-tighten control wiring lugs past factory torque limits, cracking plastic terminal block housings. Cabinet temperature cycling creates intermittent open signal circuits that only fail during peak plant load periods.Field Rule: Torque rear screw terminals to 0.6 N·m; retorque all VAJX relay wiring terminals during annual substation maintenance outage.

Commercial Availability & Pricing Note

Please note: The listed price is for reference only and is not binding. Final pricing and terms are subject to negotiation based on current market conditions and availability.