ABB OHYS2AJ Disconnector Auxiliary Contact Module

Product category: Disconnector auxiliary contact module (OHYS series), compatible with ABB OT-series disconnectors. OHYS2AJ is an auxiliary contact accessory with 2 Normally-Open (NO) contacts.

Model Code Explanation

OHYS: Series code for ABB disconnector auxiliary contacts

2: Number of contact pairs: 2 pairs

A: Contact form: NO (Normally-Open)

J: Mounting type, side-mounted, fitted onto the side of the disconnector body (not front-fitted)

✅ OHYS2AJ = 2NO side-mounted auxiliary contact

Key Specifications

1. Contact configuration: 2 × Normally-Open (NO), no Normally-Closed (NC) contacts
2. Compatible main device: ABB OT disconnectors OT16…OT125 series
3. Mounting position: Right-hand side of the switch. Maximum 2 OHYS modules per disconnector.
4. Rated electrical ratings

AC-15: 230V / 6A; 400V / 3A

DC-13: 24V / 3A; 110V / 0.6A; 220V /0.3A

5. Application purpose: Position feedback, PLC signal acquisition, cabinet door interlock and indication, circuit status signal output
6. Mechanical service life: ≥ 100 000 operations
7. Notice: Not for main power circuit; for signal auxiliary circuit only

Confusable Models in the Same Series

Installation Guidelines

1. Snap-fit into the side slot of OT16-OT125 disconnector; tool-free clip-on installation.
2. Auxiliary contact status synchronizes strictly with switch ON/OFF positions.
3. Maximum 2 side-mounted OHYS modules per disconnector. For more signals, use front-mounted OHYSxxAU.

Domestic Replacement References

Chint: NH42-AH 2NO side-mounted auxiliary contact

Delixi: HGL compatible side-mounted 2NO auxiliary contact

Replacement note: Verify mounting dimensions and travel matching; prioritize checking the disconnector base slot geometry.

Common Application Scenarios

Disconnector position feedback in power cabinets, motor cabinet power-OFF status upload to PLC, fire-linkage signals, cabinet door indicator circuits.

Main Application Scenarios of ABB OHYS2AJ (2NO Side-Mounted Auxiliary Contact)

Compatible with ABB OT16-OT125 disconnectors. 2-channel passive dry contacts for signal circuits only; do not connect to main power circuits. Mechanically follows the ON/OFF action of the disconnector.

1. PLC / DCS Remote Status Acquisition (Most Common)
2. Upload main-disconnector status in low-voltage cabinets to PLC: When the disconnector closes, OHYS2AJ contacts close and send a 24 V signal to DI modules; contacts open when disconnector opens to report power-OFF status.
3. Maintenance switch signal for motor control cabinets: When local disconnector is switched OFF, PLC recognizes maintenance status and blocks motor start-up to achieve maintenance safety interlock.
4. Centralized monitoring of multi-circuit power positions for complete plants, assembly lines and MCC (Motor Control Center).
5. Local Indicator Light Circuits
6. Cabinet-internal / door-mounted power-ON indicator: Contacts conduct when disconnector closes to light “Power ON” lamp; lamp turns off when disconnector opens.
7. Dual independent indication: Two isolated NO contacts can drive cabinet-door indicator and internal signal separately.
8. Safety Interlock Logic
9. Cabinet-door interlock: Output signal when disconnector is closed to prevent opening live cabinet doors (electromagnetic lock circuit); cabinet unlocks when disconnector opens.
10. Fire-fighting linkage: Fire-alarm system reads disconnector position for power-cut-off logic validation.
11. Equipment interlock: Mutual power interlock between two devices; closing of one disconnector inhibits energization of the other.
12. Typical Industry Applications
13. Machine tools, packaging machinery, conveyor systems: Main-power disconnector provides power-state feedback to prevent unintended start-up during maintenance.
14. Low-voltage switchgear, MCC cabinets: Disconnector position signals fed to SCADA monitoring back-end.
15. PV combiner boxes, energy-storage cabinets: Disconnector position signals sent to inverter for protection logic evaluation.
16. HVAC, water-pump & fan control cabinets: Maintenance disconnector feeds repair-mode status to control system.
17. Port, hoisting and construction-equipment electrical cabinets: Safety-switch position feedback for on-site servicing.
18. Design & Selection Notes
19. OHYS2AJ provides 2 NO contacts only, no NC contacts. For simultaneous ONand OFF-state feedback select `OHYS11AJ` (1NO+1NC).
20. Maximum 2 OHYSxxJ side-mounted modules per OT disconnector. Use front-mounted OHYSxxAU for extra signal channels.
21. Low contact rating: AC-15: 230V/6A, DC-13:24V/3A; signal-only, strictly prohibited for main circuits.
22. Passive dry-contact output; external 24 V power supply required on PLC side.
23. Unsuitable Use-Cases

Fault / alarm signal generation (module only reflects mechanical position; cannot detect overload or short-circuit).

Simultaneous opposite ON/OFF signal outputs (no NC contacts available).

High-current load circuits.

Engineering Application Cases for ABB OT Disconnector OHYS-Series Auxiliary Contacts

Covered models: OHYS2AJ (2NO side-mounted), OHYS11AJ (1NO+1NC side-mounted), OHYS2AU (2NO front-mounted). All are passive dry-contact signal feedback accessories compatible with OT16-OT125 disconnectors.

Case 1: MCC Motor Control Center Cabinet (Factory LV Distribution Room)

Configuration: OT63 disconnector + OHYS2AJ (2NO side-mounted auxiliary contact)

Circuit: Disconnector serves as maintenance disconnect point for individual motor feeder circuit.

Wiring: One NO channel to PLC-DI for disconnector ON-status upload; second NO channel to cabinet-door “Power ON” indicator lamp.

Logic:

1. When disconnector is opened, PLC receives signal and locks motor in maintenance inhibit state.
2. When closed, indicator lamp illuminates and motor start-up is permitted by PLC.

Design consideration: Only ON-position feedback required; use OHYS2AJ. Select OHYS11AJ if both ON and OFF status must be reported.

Site benefit: Side-mounting saves front-of-cabinet space; clip-on fast installation for high-density MCC cabinets.

Case 2: Cabinet-Door Electromagnetic-Lock Safety Interlock (Machine-Tools / Assembly Lines)

Configuration: OT100 disconnector + OHYS11AJ (1NO+1NC)

Purpose: Main-power disconnector implements live-chamber door-opening prohibition interlock.

Wiring: NO contact drives electromagnetic-lock coil. When disconnector closes, NO closes and energizes lock to secure cabinet door against opening under voltage; disconnector opens → NO opens → lock de-energizes for service access.

⚠️ OHYS2AJ cannot be used here: it has only NO contacts and cannot capture OFF-state. Use OHYS11AJ (1NO+1NC).

Safety value: Prevents personnel exposure to live parts; complies with machinery-safety requirements.

Case 3: Commercial & Industrial PV Grid-Tie Cabinet

Configuration: OT80 disconnector + OHYS2AJ

Scenario: AC output-side disconnector of grid-tied inverter.

Wiring: Two NO dry-contact channels: one to inverter controller for external disconnector ON confirmation; second channel to SCADA for remote disconnector-status visualization.

Logic: Disconnector open → inverter receives signal and blocks grid-tied output; back-end SCADA updates icon status for remote operational awareness.

Selection rationale: Only closed-position confirmation needed; OHYS2AJ offers cost advantage.

Case 4: Water-Pump & Fan Control Cabinet (HVAC, Waste-Water Plants)

Configuration: OT40 disconnector + OHYS2AJ

Application: Local maintenance disconnector for circulating pumps and exhaust fans.

Signal assignment:

1. First NO channel to PLC: power-ON confirmation enabling pump operation.
2. Second NO channel to DCS for remote status transmission.

Process logic: Operator opens disconnector for maintenance; PLC inhibits both local and remote pump start-up to avoid accidental actuation.

Case 5: Multi-Signal Expansion on Single Disconnector

Configuration: OT125 disconnector fitted with two OHYS2AJ side-mounted modules

Hardware limit: Maximum 2 side-mounted OHYSxxJ modules per OT disconnector.

Four NO-contact allocation:

1. 2 channels for PLC input;
2. 1 channel for local indicator lamp;
3. 1 channel for third-party fire-protection monitoring system.

When side slots are fully occupied, add front-mounted OHYSxxAU to expand I/O capacity combining side + front accessories.

Case 6: Energy-Storage PCS Grid-Tie Cabinet

Configuration: OT100 disconnector + OHYS11AJ

Requirement: EMS energy-management system needs both ONand OFF-position information.

NO signal: PCS grid-tied operation enable.

NC signal: Reports maintenance OFF-state; EMS blocks charge-discharge functions.

Important: Safety logic for energy-storage requires dual-state feedback; OHYS2AJ is not suitable.

Quick Engineering Selection Reference

Common Engineering Pitfalls

1. OHYS2AJ has no NC contacts. Do not misapply for cabinet-door interlock or energy-storage safety circuits.
2. Auxiliary contacts are passive dry-contacts; external 24 V supply must be provided on PLC side; no power source inside module.
3. Limited contact rating AC-15:230V/6A; strictly for signal circuits only, never main power circuits.
4. OHYS2AJ is incompatible with OT160 and larger disconnectors; select dedicated accessories for high-frame OT devices.

Operating Principle of ABB OHYS-Series Auxiliary Contacts (based on OHYS2AJ)

OHYS are mechanical passive auxiliary contacts. No coil and no internal power supply. Operate purely by mechanical coupling with OT disconnector shaft; output dry-contact signals representing mechanical handle position only. They do NOT sense current, faults or electric arcs.

1. Mechanical Coupling Principle
2. Rotation of OT disconnector operating handle drives main shaft through 90° rotation to close / open main-power contacts.
3. OHYS2AJ clips onto disconnector side; internal drive lever engages shaft cam profile and rotates synchronously with main shaft.
4. Main-shaft rotation actuates OHYS internal lever, deflecting miniature silver-contact spring assemblies to switch contact states.
5. Galvanic isolation between auxiliary-contact circuit and main power circuit: only mechanical linkage exists, no electrical connection.

Timing characteristic: Auxiliary-contact state changes only after main power contacts complete mechanical travel. Prevents false “closed” signals before main contacts are fully seated.

2. Contact Action Logic for OHYS2AJ (2NO)

Two independent Normally-Open dry-contact channels inside OHYS2AJ:

Disconnector OFF: Lever unloaded; both NO contacts remain open; no continuity across terminals.

Disconnector ON: Shaft actuates internal lever compressing contact springs; both NO contacts close simultaneously establishing passive continuity.

⚠️ OHYS2AJ contains no NC contacts. Select OHYS11AJ (1NO+1NC) if OFF-position closed signal is required.

Action Comparison for OHYS11AJ (1NO+1NC)

ON position: NO closes, NC opens

OFF position: NO opens, NC closes

Complementary contact states for simultaneous ONand OFF-position reporting.

3. Electrical Principle (Passive Dry-Contact)

The module itself is a mechanically-actuated switch element without power supply:

1. External secondary power source (DC24V / AC230V) is wired via PLC-DI, indicator or solenoid load to OHYS terminals.
2. Disconnector closes → contacts conduct → circuit energized → external device receives ON signal.
3. Disconnector opens → contacts interrupt → circuit de-energized → signal removed.

Contact capacity limited: AC-15 230V/6A; DC-13 24V/3A. For secondary signal circuits only; forbidden for main power paths.

4. Key Technical Characteristics
5. Pure mechanical follow-up: Actuation driven by manual handle movement; auxiliary contacts switch whenever handle reaches mechanical ON/OFF position.
6. Represents mechanical position only: If main contacts are burned or have poor contact, auxiliary contacts still follow handle position. Cannot verify actual presence of voltage on main circuit.
7. Multi-module expansion: Up to two side-mounted OHYSxxJ units; additional channels by stacking front-mounted OHYSxxAU.
8. Galvanic separation: Auxiliary circuits are insulated from main power circuit, avoiding cross-coupling between high-power and control systems.
9. Principle-Related Engineering Misconceptions
10. ❌ Myth: Auxiliary contacts can detect live voltage.

✅ Reality: Reacts only to handle position; reports “closed” even if upstream main circuit is de-energized.

2. ❌ Myth: OHYS2AJ can deliver both ON and OFF opposing signals.

✅ Reality: Two NO channels open simultaneously at OFF state; use NC-equipped variant for OFF-state signal.

3. ❌ Myth: Auxiliary contacts can directly drive high-power loads.

✅ Reality: Low-power signal contacts; intermediate relay required for heavy loads.

Simple Analogy

Comparable to a magnetic door-contact switch: Door closed (disconnector ON) → switch conducts; door open (disconnector OFF) → switch opens. It detects mechanical position, not whether there is voltage behind the door.