RS PRO 504-139 Isolating Transformer 200VA 230V ST53334

RS PRO 504-139 Isolating Transformer (ST53334) – 200VA, 0–230V AC Output

The RS PRO 504-139 (Manufacturer Code: ST53334, Batch/Date Ref: 35/09) is an industrial-grade, single-phase chassis-mounting safety and isolating transformer engineered for critical control circuits, automation panels, and marine electrical infrastructure. Delivering a continuous rating of 200VA, this unit provides galvanic isolation between dirty mains supplies and sensitive downstream loads, eliminating ground loop current, attenuating common-mode electrical noise, and preventing fault propagation.

Built with heavy-duty grain-oriented electrical steel laminations and full vacuum-varnish impregnation, the transformer resists ambient salt fog, high humidity, vibration, and thermal cycling common in marine engine rooms, switchgear cabinets, and industrial plant rooms. It features multi-tap primary terminals compatible with standard 230V single-phase, 400V line-to-line systems, and a dedicated +15V compensation tap to offset distribution line voltage drop.

Model Details

• Manufacturer / Brand: RS PRO
• RS Stock Number: 504-139 (or 504139)
• Manufacturer Part Number (MPN): ST53334
• Production / Manufacturing Stamp: 35/09
• Distrelec Article Number: 304-04-316
• EAN / UPC: 5056070926806

Technical Specifications

Key Features

1. Complete Galvanic Isolation: Fully isolates secondary circuits from supply grounding structures, stopping circulating ground loops and transient spikes.
2. Multi-Voltage Primary Tappings: Dual primary winding accepts 230V or 400V systems with an integrated +15V auxiliary tap to trim for line voltage drops (supports 230V, 245V, 400V, and 415V AC).
3. Marine-Grade Varnish Impregnation: Industrial varnish dip-and-bake process seals the core against condensation, salt atmosphere, and vibrational hum.
4. Touch-Proof Terminal Blocks: Fully shrouded screw-cage terminations prevent accidental finger contact while offering permanent terminal labeling.
5. High Efficiency & Low Regulation: Low-loss laminations ensure nominal voltage output holds steady from zero load up to the full 200VA envelope.

Compatibility

• Industrial & Marine PLC Cabinets: Siemens S7, Allen-Bradley ControlLogix, Schneider Modicon, and Omron rack power feeds requiring clean 230V line-neutral separation.
• Marine Automation Systems: Kongsberg, Wärtsilä, and ABB propulsion monitoring consoles and alarm/monitoring systems (AMS).
• Navigation & Bridge Electronics: Gyrocompasses, radar display modules, AIS receivers, and ECDIS units requiring isolated 230V supplies.
• Solenoid & Contactor Coils: Feeds 230V AC control circuits for marine bow thruster starters, bilge pump switchgear, and air compressor contactors.

Applications

• Marine engine room control consoles and local motor starter panels
• Shipboard IT/navigation distribution boards where IT grounding networks are isolated from ship hull steel
• Industrial machine tools and CNC control interlocks
• Medical instrumentation and test bench isolating stations
• Acoustic and transducer equipment sensitive to primary harmonic distortion

Part Number Cross-References

• RS Components: 504-139 / 504139
• Distrelec: 304-04-316 / 30404316
• Block Transformatoren: Comparable to CT 200/23/23 or TIM 200 series
• Legrand: Functional equivalent to 0 442 33 control isolating transformer series

Frequently Asked Questions

What is the primary difference between an autotransformer and the RS PRO 504-139 isolating transformer?

An autotransformer shares a single continuous winding between primary and secondary, offering zero electrical isolation. The RS PRO 504-139 features distinct, electrically separated primary and secondary coils (galvanic isolation). This eliminates common ground loops, protects sensitive automation from primary voltage spikes, and ensures personnel safety.

How do I use the +15V terminal on the primary winding?

The +15V tap allows fine-tuning of the turns ratio when nominal line voltages exceed standard baselines. Wiring across +15V and 230V accommodates a 245V feed, while wiring across +15V and 400V accommodates a 415V supply, preventing over-voltage on secondary control coils.

What is the maximum secondary output current of this transformer?

Rated at 200VA with a 230V AC secondary, the continuous maximum full-load output current is approximately 0.87 Amperes Operating continuously above 0.87A risks thermal overload and insulation breakdown.

Can this transformer operate on both 50Hz and 60Hz marine electrical grids?

Yes. The magnetic core has sufficient flux density margin to run on both 50Hz shoreside power and 60Hz marine vessel distribution without core saturation or overheating.

Is the secondary winding center-tapped?

Yes, the secondary features a center-tapped winding layout. This allows the user to ground the center tap to create a balanced supply (e.g., 115V-0-115V relative to earth) or leave it isolated to maintain an unearthed floating system.