Plating Rectifiers

Plating Rectifiers

Today’s rectifiers operate on foundational principles that have remained consistent for decades. Although there have been significant improvements in manufacturing techniques and materials, the core principles are unchanged. The most remarkable advancements are linked with electronics and computerization.

Click here to get more.

Key Components of Rectifiers

Every rectifier includes the following components:

• A transformer that reduces a utility's high voltage to the 6-18 volts typically required by electroplaters or the higher voltages needed by anodizers.
• A rectification system that converts alternating current (AC) to direct current (DC).
• Power regulators and controls.
• A cooling mechanism for these parts.

With the exception of the cooling section, rectifiers have no moving parts.

Transformers

A transformer consists of primary and secondary magnetic cores wound with conductive wire. The ratio of wire turns between the primary and secondary cores determines the voltage reduction. For example, with 400 turns on the primary and 10 turns on the secondary, the ratio is 40:1, meaning 480 volts input results in 12 volts output. Most plating processes require 6-18 volts, and rectifiers delivering this at 50-10,000 amperes or more are readily available.

Rectification and Control

AC generates a waveform that alternates above and below the horizontal axis. The rectifier filters out the lower part of the wave, resulting in half-wave rectification. This form of rectification is pulsating. Full-wave, single-phase rectification, while also pulsating, occurs at closer intervals. Full-wave, three-phase rectification exhibits minimal pulsation, typically less than 5%, which suffices for most electroplating processes.

Modern rectifiers use semiconductors, primarily silicon, to filter out AC and allow only DC to flow. Simple devices accomplishing this are known as diodes. Silicon-controlled rectifiers (SCR), or thyristors, add regulation capabilities by needing a control signal at a terminal or gate. Depending on design, SCRs can be used for rectification and regulation, either on the primary or secondary side of the transformer. Your rectifier supplier should recommend an optimal setup based on your application's needs.

Ripple

A downside of SCRs is the production of ripple—remaining fluctuations in the DC. Larger rectifiers usually produce ripple of 5% or less at rated capacity. Operating significantly below capacity increases ripple. Plating specific metals like chromium and precious metals requires minimal ripple, which may necessitate adding a ripple filter. For more routine processes like electrocleaning, electropolishing, and anodizing, ripple is less crucial.

Alternative Control Methods

A tap switch offers a simple alternative to solid-state controls by switching between varying numbers of wire windings in the transformer. This method can produce DC with minimal ripple but may suffer from voltage fluctuations, problematic for precision plating. A variable autotransformer provides continuous variation without taps.

Switch-Mode Power Supplies

Switching transistor-type rectifiers use an EMI filter to rectify and filter incoming power, converting it to DC. An inverter then converts it back to AC at high frequencies, which is stepped down and rectified again to produce a low-voltage, high-current output with very low ripple. These units, being compact and lightweight, can be wall-mounted or fit into spaces unsuitable for conventional units.

Computerization

The introduction of microprocessors and digital components has revolutionized rectifier technology, allowing for precise control of amperage and voltage. Digital rectifiers can ramp up current as parts enter plating or anodizing tanks, perform pulse plating, control ampere-hours, and reverse current—all while being programmable for complex waveforms. These systems can be managed via computer interfaces for enhanced efficiency.

Computerization not only optimizes current usage and reduces costs but also ensures consistency and minimizes labor. Detailed memory logs also facilitate troubleshooting upon any part rejection, providing insights into operational conditions.

Anodizing

Anodizing processes require rectifiers similar to those used in electroplating but capable of handling higher voltages, up to 150 volts for hard-coat anodizing. Specific processes may need both AC and DC power supplies, programmable for rapid voltage and polarity adjustments.

Pulse Plating and Periodic Reverse

Pulse plating involves quickly interrupted direct current and can be used with periodic reverse for denser, smoother deposits with fine crystal structures. These techniques, initially developed for electronics, now extend to electropolishing, electrocleaning, and barrel plating. Advanced rectifiers for such applications offer programmable currents from milliamperes to thousands of amperes, including forward, reverse, and pulsed current combinations.

With competitive pricing and timely delivery, Kehong sincerely hopes to be your supplier and partner.

Rectifier Placement

Placing the rectifier close to the plating tank minimizes current loss and maintenance. Cooling the rectifier, especially in corrosive environments, might require installing it on the other side of the wall or using air-tight water-cooled units. Rectifiers are designed to operate within specific temperature ranges, making water cooling mandatory if ambient air exceeds these temperatures.

Maintenance and Repair

Rectifiers, besides cooling fans or pumps, lack moving parts and can last long with proper maintenance. Regularly changing or cleaning air filters, ensuring unobstructed airflow, securing fan blades, maintaining water pumps, and keeping semiconductors clean are crucial. Control instruments should be checked and replaced as needed. Many rectifiers have onboard diagnostics to identify issues.

Ammeters, voltmeters, and oscilloscopes help identify problems, and suppliers provide detailed manuals and parts lists to facilitate repairs, requiring an understanding of electrical equipment and safety concerning high voltages and currents.

Buying a Rectifier

When purchasing a rectifier, consider its reliability, repeatability, conversion efficiency, low maintenance costs, excellent warranty, ease of installation, and expandability. Establishing trust with your supplier and seeking peer recommendations can help. Create a wish list of features to improve quality and performance in your specific applications.

For further information on Precious metal plating rectifier factory, feel free to contact us.

Argon Masking Corp., EPSI, Caplugs, Polymer Molding Inc.