Plating IGBT Rectifiers
1. Plating Rectifier Rated Voltage
When the pole spacing of the plating tank and the anode area are fixed, the current density of the plated workpiece is generally proportional to the applied voltage. If the voltage is insufficient, the current density is low. Therefore, the upper limit of the DC voltage required by the plating tank must meet the maximum working current of the plating tank required by the highest current density.
Voltage adjustment range: the upper limit value should be equal to the upper voltage limit of the plating tank plus the voltage drop of the busbar: the lower limit value should be equal to the lower voltage limit of the plating tank and the voltage drop of the busbar. In actual production, a rectifier with a larger voltage adjustment range is often selected to meet the needs of different process configuration changes.
However, when the actual working voltage is much different from the rated voltage of the rectifier, it will seriously reduce the efficiency of the rectifier and cause waste of electric energy. In particular, the capacity of electroplated rectifiers is generally big, so the waste of electrical energy cannot be ignored.
In addition, for the thyristor rectifier, when the actual operating voltage is much different from the rated output voltage, not only the efficiency is low, but also the output DC current fluctuation becomes bigger, in some cases it may affect the plating quality, so in the process under stable conditions, a slightly higher voltage of the rectifier is necessary, but it should not be too much different.
According to the rectifier equipment standard for electroplating, the voltage regulation range of the rectifier can be continuously adjusted at 30% of the rated voltage, and ensure that at 66% and above of the rated voltage, it should be able to continuously operate at 100% of the rated DC current and at the rated voltage When operating below 66%, it must be able to carry at least 50% of the rated output current. For example, the resistance of the nickel plating solution is small, and the current required by the process can be reached with a very low voltage. Therefore, when selecting a nickel-plated rectifier, the actual required tank voltage is 3 ~ 4V. Considering the DC bus voltage drop and other factors, choose 6V The rectifier is suitable. When the voltage is adjusted to 4V in production, the load rate is 66%, and the current waveform can also be within the smooth range: if you choose a 12V rectifier, you will not get a smooth waveform, and you will not get a dense and smooth Nickel plating.
2. Plating Rectifier Rated Current
The rated current of the rectifier should be equal to or slightly larger than the maximum working current of the plating tank, which can be calculated by the following formula:
In the formula IC-Rectifier rated current, A;
DK-Cell current density, A/dm2
Smax-Total area of workpieces in the plating tank, dm2。
Considering that the un-insulated parts of the hanger will also consume current, when the workpiece are more complicated, a larger current will be concentrated at the corners. Therefore, in order to ensure that the workpiece can reach the current density required by the plating process, the total area of the workpieces should be increased by 5% when calculating the rated current of the rectifier. Therefore, when selecting the rectifier, it is not necessary to increase too much additional value of the current, which not only saves energy but also saves investment.
3. DC voltage and current density required for different plating
Table 1 DC voltage and current density required for different plating
Processing plating name
(A / d㎡)
Cell voltage V
Decorative chrome plating
Hard chrome plating
Black chrome plating
Dark chrome plating
Semi-bright nickel plating
Semi-bright nickel plating
Black nickel plated
Barrel nickel plating
Sulfate zinc plating
Ammonium chloride zinc plating
Potassium chloride zinc plating
Potassium chloride barrel zinc plating
Pyrophosphate copper plating
Copper sulfate plating
Acid tin plating
Alkaline tin plating
Alkaline barrel tin plating
Non-cyanide silver plating
Sulphite gold plating
Electrolytic nickel removal
Aluminum Sulfate Anodizing
Aluminum chromic acid anodizing
Aluminum sulphate hard anodizing
Aluminum mixed acid hard anodizing
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