Power transformer guide: PQ, RM cores, mains-frequency for adapters, industrial supplies, inverters. ADD stocks TDK, Wurth, Eaton, Hammond. Buy power transformers online.
Power Transformers — PQ, RM and Mains-Frequency Transformers
Power transformers handle the highest energy levels in a design, converting AC mains or intermediate DC rails into the voltages a system requires. They range from compact ferrite PQ and RM core transformers used inside switch-mode power supplies to traditional laminated-core mains transformers that step 115/230 VAC directly down to a low-voltage secondary at 50/60 Hz. ADD Components is a professional electronic components distributor supplying power transformers from TDK, Wurth Elektronik, Eaton and Hammond for mains adapters, industrial power supplies, inverters and battery chargers. This guide reviews the principal power transformer types, the key selection parameters and representative part numbers for teams buying power transformers online.
Product Types / Variants
PQ Ferrite Core Transformers
PQ cores feature a round centre leg and a large, low-profile winding window that maximises power density for a given board footprint. They are the preferred choice for compact, higher-power switch-mode transformers, including the PQ2014 size (PQ20/16) widely used in 20–50 W flyback and forward converters. PQ-core transformers combine low copper loss, good shielding and excellent thermal performance, making them ideal for compact mains adapters, notebook chargers and industrial SMPS where size and efficiency are both critical.
RM Ferrite Core Transformers
RM (rectangular modular) cores are essentially pot cores with the corners removed to open the winding window for easier termination while retaining strong shielding and low electromagnetic interference. They suit low- to medium-power converters, telecom DC-DC modules and filter/transformer applications where a compact, self-shielding magnetic part is required. RM5, RM6, RM8 and RM10 sizes cover a broad power range and are available with a variety of ferrite materials and air-gap options.
Mains-Frequency (Laminated Core) Transformers
Mains-frequency transformers operate directly at 50/60 Hz using laminated silicon-steel cores and are valued for their simplicity, robustness and excellent isolation. They convert 115/230 VAC to a safe low-voltage secondary with no switching electronics, making them a reliable choice for linear power supplies, control panels, audio equipment and test instrumentation. Hammond Manufacturing's 185, 186 and 187 series are representative mains transformers that ADD Components sources for industrial and professional applications.
High-Power and Inverter Transformers
High-power transformers for inverters, motor drives and industrial power supplies must handle large currents and high voltages with low losses and reliable insulation. They span large ferrite and laminated cores and are specified by VA rating, operating frequency and isolation class. ADD Components sources high-power ferrite transformers from TDK and Wurth Elektronik together with Eaton's Versa-Pac power transformers for DC-DC and inverter stages in renewable-energy, UPS and industrial automation equipment.
Key Selection Parameters
Power Rating (VA or W): The continuous apparent-power or real-power rating must exceed the load with margin for ambient temperature and duty cycle.
Operating Frequency: 50/60 Hz mains parts versus ferrite transformers designed for 20 kHz–1 MHz switch-mode operation — material choice depends on this.
Core Type and Size: PQ, RM or laminated core — selected for power level, footprint, height and shielding (e.g., PQ2014/PQ20/16, RM8).
Primary Voltage: Single (115 V) or dual (115/230 V) primary configuration for the intended mains input.
Secondary Voltage and Current: Output voltage(s), centre-tap options and current per winding determine turns ratio and wire gauge.
Isolation and Withstand Voltage: Confirm dielectric strength (e.g., 4 kV for mains parts) and compliance with safety standards such as IEC 62368-1 or UL.
Regulation: Load regulation (voltage drop from no-load to full-load) is critical for linear supplies and sensitive analog circuits.
Package and Termination: Chassis/through-hole mounting versus PCB/SMT; confirm lead style, spacing and any required mounting hardware.
Representative Transformers We Source
| Part Number | Brand | Type | Key Spec |
|---|---|---|---|
| B65671D0000R048 | TDK (EPCOS) | PQ20/16 (PQ2014) ferrite core | N48 low-loss power material |
| B65805J0000R087 | TDK (EPCOS) | RM5 ferrite core | N87 material |
| B65811J0000R087 | TDK (EPCOS) | RM8 ferrite core | N87 material |
| 750342928 | Wurth Elektronik | MID-PPTI push-pull | 1:1.3, 6 W |
| 750313734 | Wurth Elektronik | WE-FLEX offline | 12 W |
| VP1-0059 | Eaton (Coiltronics) | Versa-Pac transformer | 6 windings, configurable |
| VP3-0138 | Eaton (Coiltronics) | Versa-Pac transformer | 6 windings, higher power |
| 187B56 | Hammond Manufacturing | Mains transformer | 56 VA, 115/230 V to 24 V CT |
| 185C24 | Hammond Manufacturing | Mains transformer | 25 VA, 24 V CT |
| 186B12 | Hammond Manufacturing | Mains transformer | 30 VA, 12 V CT |
Send Us Your Transformer Requirements
ADD Components is a Hong Kong-based electronic components distributor supplying power transformers to OEM, EMS and contract manufacturing customers worldwide. We source PQ and RM ferrite-core transformers together with mains-frequency and high-power transformers from TDK, Wurth Elektronik, Eaton and Hammond Manufacturing, covering mains adapters, industrial power supplies, inverters and battery chargers. Every transformer ships with factory traceability, date-code verification and anti-counterfeit screening.
Send your part numbers, target pricing or full bill of materials to Info@addcomponents.hk for a same-day quotation. We support spot buys, blanket orders and power transformer wholesale programs, and we can recommend pin-compatible alternatives to consolidate your BOM and shorten lead times.
Email: Info@addcomponents.hk | Tel: +852 5334 3091 | WhatsApp: +852 5334 3091
Last updated on September 11, 2026