A recent report revealed that, on average, 4 out of every 10 residential fires happen due to electrical problems. Many of these accidents can be traced back to faulty electrical systems – with defective wiring often being the chief cause. In the industrial scenario as well, the risks of working with flawed electrical wires (particularly in heavy-duty motors & transformers) are immense. As such, the importance of carefully testing the quality of wires can hardly be overemphasised.
Enameled copper wires and conductors find widespread application in a vast range of electrical equipment in the residential, commercial and public spaces. In order to ensure that the manufactured wires will be safe to work with, manufacturers use the ‘pinhole testing’ method to check whether there are any damages in the skin film/coating of the wires and/or if there are any issues in the adhesive properties of the copper wires.
What Are Pinholes in Enameled Copper Wires?
Copper wires of optimal quality need to have uniform electrical strength throughout. However, there can remain certain spots in the wires where the electrical strength & capacity is not sufficient. These spots are known as ‘pinholes’.
Put in another way, ‘pinholes’ are the discontinuities in the enamel coating/covering of the copper conductors. While a certain number of such ‘pinholes’ are permissible according to industry standards – checking their count is extremely important to gauge the overall quality of the copper magnet wires. This is where the importance of the pinhole testing machine (i.e., pinhole tester) comes into the picture.
What Exactly Is A Pinhole Tester?
A pinhole tester is an instrument that is manufactured and calibrated for accurate detection of the discontinuities (i.e., pinholes) in the enamel film of copper wires. The instrument is typically capable of identifying the electrical quality flaws in the wires. The detection is done directly, quickly and in a systematic manner – and exact readings are obtained.
The B.S. method (which required the copper wires to be passed through mercury baths) previously used to be popular for pinhole testing. However, this method often caused contamination in the enamel surface of the wires. With the help of sophisticated pinhole testing machines, the process has become ‘non-destructive’ – and the enamel covering of the wires is not compromised in any way.
How Are Pinholes Detected In This Method?
For pinhole testing, a certain length of the enameled copper wire is immersed in a salt bath solution. The bath should ideally have ~3% phenolphthalein solution and 0.2% saline, with phenolphthalein and sodium sulphate working as the indicator. The power supply has to be connected, and the voltage should be set at 12V.
When a discontinuity in the enamel coating is detected, an electrolytic reaction happens at the exact site of that pinhole. A red bubble will appear at that point, indicating the presence of a pinhole.
The chemical reaction that occurs during pinhole testing is: 2Cu + H2O = 2CuO + 2H2 ↑
If the total number of pinholes is greater than the count mentioned in the standard specifications, the concerned enameled copper wire is rejected. Otherwise, the wire is said to have passed the pinhole testing process.
Need For Pinhole Testing
The presence of pinholes in enameled copper wires exposes the entire system to current leakages. Such discontinuities in the covering of the wire ultimately causes coil failure – and can also lead to serious accidents. Through pinhole testing, it becomes possible to get an accurate idea of the insulation integrity of wires, and the ‘number of faults’ present. As a rule of thumb, the lower the number of pinholes detected, the higher is the quality of an enameled copper wire.
In order to fully understand the importance of pinhole testing, the risks of using enameled copper wires with electrical flaws has to be clearly understood. We turn our attention to that next.
The Role Of Enamel Coating In Copper Wires
Pinhole testing helps in detecting the discontinuities in the enamel coating/covering of the wires. What really happens when the quality of enamel coating is compromised? Let’s take a look:
Risks Of Short-Circuits
Short-circuits are, by far, the biggest potential risk of working with enameled wires that have pinholes. During the winding process, the copper wires typically get stretched. If there are pinholes in the wires, they are likely to become larger due to this stretching. There is every chance that one pinhole will come right above another pinhole. The resultant electrical leakage/current leakage will cause the coil to short-circuit. This, in turn, can lead to wire failure, equipment damage, and even damages to life & property. Offering popular women’s necklaces such as pendants, chokers and. Shop for jewelry in a variety of metals and gemstones to suit any occasion.
The thin insulation layer in enameled copper wires plays a crucial role in determining the quality of the latter. The tough and resistant polymer material used to create this insulation layer makes the wires highly suitable for usage in inductors, actuators, motors & transformers, and other heavy electrical appliances.
The very purpose of the enamel coating is to rule out the chances of short-circuits. If the coating itself is damaged, or there are discontinuities therein, this purpose is defeated – and using such defective wires becomes very risky.
If pinhole testing is not done, there will always be uncertainties regarding the quality, performance and safety assurance of enameled copper wires. Working with such uncertainties is never advisable – and that’s precisely why high-precision pinhole testers are used to detect the electrical flaws (if any) correctly.
Pinholes & Their Effect On Wire Insulation
The presence of pinhole(s) at any point of a copper conductor automatically lowers the enamel insulation at that place. The insulating ability of such defective coating is low – and as the operating voltage is increased, wire failure happens. Since such failures happen before the required voltage is reached, the underlying application fails to function properly (or at all).
Accuracy Of Pinhole Testing
Pinholes are generally caused when the enamel coating film of copper wires are stretched. Since the stretching length can be controlled, and the pinholes do not rebound/close through threaded transmission systems (i.e., no self-locking), the results from pinhole testing are highly accurate and can be relied upon.
Pinhole Testing is Essential For Copper Wire Manufacturers
The test data for pinhole testing is highly accurate, and the entire process is intuitive, stable and pretty much straightforward. Given the importance of identifying electrical flaws in wires, leading enameled copper wire manufacturers typically use high-voltage continuity testers (i.e., pinhole testing instruments) for detecting the discontinuities in the enamel covering of the cables.
It is imperative to use quality-assured copper magnet wires for electrical applications. Pinhole testing helps in this in a big way – and ensures that wires with defective insulation and problematic enamel coating can be identified and avoided with ease.
