Magnet wire is a copper wire coated with high-quality enamel. It appears quite straightforward, right?

Yet, a minor variation in the quality and quantity of the conductor or insulation can make it unfit for a specific application. Be it a high-performing electric vehicle motor or an energy-efficient BLDC fan motor.

Let us see what happens when proper insulation is not there in the magnet wire.  Defects like small cracks in the enamel insulation can lead to problems such as electrical breakdown, overheating, and mechanical failure of the motor. Or in other words, your customer finds the product (motor) less reliable, affecting the brand perception.

So, to win customer satisfaction with better efficiency and long life of motor, the winding wire has to meet the required enamel specifications. Quality-focused magnet wire manufacturers follow a series of quality checks to affirm the same. Tan Delta test is one such test that ensures the quality of enamel insulation in magnet wire.

What is Tan Delta?

Tan delta indicates the degree of curing of the magnet wire. Every enamel has a recommended tan delta which is best suited for wire properties.

During the curing process, the enamel insulation is heated to a high temperature in order to crosslink the polymer molecules and form a continuous, protective layer around the wire. If the enamel is not fully cured, it may have defects such as voids, cracks, or contamination.  These can affect the electrical insulation properties of magnet wire, viz:

1. Increased electrical resistance: Defects in the insulation can increase the electrical resistance of the winding wire, which can cause the motor to overheat and eventually fail.
2. Decreased efficiency: Defects in the insulation can also cause the motor to be less efficient, as more energy is lost due to the increased electrical resistance.
3. Increased maintenance: If defects in the insulation are not detected and repaired, the motor may require more frequent maintenance to address problems caused by the defects.

 

(Also Read: Common Problems in Winding Wires)

Tan Delta testing is an accurate way to identify such defects in the insulation in magnet wires.

Quality Testing for Magnet Wires – Tan Delta Testing

Tan delta testing, also known as dielectric loss tangent testing or dissipation factor testing, is a method used to measure the electrical insulation properties of winding wires.

It involves applying a high-frequency alternating voltage to the winding wire and measuring the resulting current. The ratio between the alternating voltage and current is known as the “tan delta” value. It indicates the amount of energy lost due to resistance and capacitance within the wire.

This value can be used to determine the condition of the wire.  Specifically, to identify any defects or damage that may be present in the insulation.

A low tan delta or dissipation factor indicates that the insulation of the winding wire is good. In other words, it has a low level of electrical resistance. On the other hand, high values indicate that the insulation is not performing well, due to improper curing.

Right Ways to Measure Tan Delta in Winding Wire

Tan delta can be measured using 2 types of techniques

• Woods alloy method (reducing temperature) and
• Graphite method (increasing temperature).

 

The latter is the correct way, as it indicates any trapped solvents or cross-linking which hasn’t taken place during manufacturing. While in the former, since the sample is pre-heated to a higher temperature, there is a tendency to hide these defects.

Likewise, the R&R (Repeatability and Reproducibility) of the Tan delta is also of utmost importance. And above all, for accurate results usage of quality measuring instruments are a must.

Tan Delta Testing at Geekay to ensure high-quality insulation

At GEEKAY we use the Tan Delta with Graphite method and we have Tan Delta testing equipment from one of the best manufacturers in the world known for quality instruments. We also do a few more quality tests for concentricity, inline diameter and pinhole to ensure the consistency of enamel coating throughout. And we are proud to say that we source our enamel from reliable sources – Elantas, Fupao and Huber.

 

By ensuring quality controls at every step of the manufacturing process, we are able to provide high-quality magnet wires of exact electric specifications customised for your products.