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What is a Rectifier?

Power supplies come in all sizes and types. This will help you determine which are suitable for electroplating and anodizing and which are not.

Power Supplies or Rectifiers The term rectifier was used to describe power supplies in the 19th.Century. Electronics wasn't invented yet so power supplies as we know them didn't exist. In spite of not being used for 100 years the name rectifier stuck, and power supplies used for plating and anodizing purposes are called this in the Industry.

Regulated and Non-Regulated Power Supplies A regulated power supply has a circuit to hold its output to a particular value when the load on the power supply changes. A non-regulated power supply does not have this circuit so its output will change as the load changes. A common example of regulated would be the power supply in your personal computer. An automotive battery charger would be an example of a power supply with no regulation.

Adjustable and Non-Adjustable Power Supplies

An adjustable power supply has a control to allow the user to adjust its output, and a non-adjustable power supply does not. Your computer power supply is non-adjustable and so is your battery charger. All plating and anodizing rectifiers are adjustable, as are laboratory type electronics power supplies. For all plating and anodizing purposes, an adjustable power supply is required.

Power Supply Regulation, CV and CC Methods

There are two regulation methods in common use, Constant Voltage (CV) and Constant Current (CC). Constant Voltage (CV) regulation has the means to measure its own output voltage, and a circuit that compares this to a reference voltage set by the user (the Volts knob). Regulation is achieved by the power supply constantly adjusting its output voltage so that it matches the user set reference. Hence the name, Constant Voltage. This will operate up to the maximum current capability of the power supply, called its current limit. Constant Current (CC) regulation has the means to measure its output current, and a circuit to compare this current to a reference current set by the user (the Amps knob). Regulation is also achieved by the power supply constantly adjusting its output voltage, but this time so that the output current matches the user set reference current. Hence the name Constant Current. This regulation is maintained up to the maximum voltage the power supply is capable of, this limit is called the power supply's maximum voltage compliance. Laboratory type power supplies often have both types of regulation and can operate in either CV or CC modes. Caswell's 3 Amp and 30 Amp CV/CC rectifiers are examples of these.

Power Supplies for Plating

A CC power supply is clearly the easiest and best type to use for any plating application. Many of the electrical problems encountered by new platers can be avoided entirely by using CC. Not the least of these problems is plating at a consistent current; as the plating process continues, small changes in electrical characteristics of the plating setup occur which cause significant changes in the plating current. This in turn can cause uneven plating thickness and poor plating adhesion. These changes are unavoidable, and with CC operation the power supply compensates for them automatically, requiring no action or adjustments by the plater. For this reason Caswell Inc. recommends the use of CC for any and all electroplating applications.

Power Supplies for Anodizing

A CC power supply also greatly benefits anodizing. Since anodize is an insulator, the changes in electrical characteristics during the process are much larger than in plating. CC operation provides a uniform anodize pore structure all the way down to the base metal. This promotes even and deep dye penetration, and the consistent pore structure provides a better looking and stronger anodize coating than if the pores are distorted by changes in the current. For this reason Caswell Inc. recommends the use of CC for any and all anodizing applications.

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  1. Lance Caswell

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