In our previous article on Testing of Enamelled Winding Wires, we had outlined some of the common problems which can occur due to poor quality or standards of the wire. In this article we will discuss about the various tests for Enamelled Winding Wires.
Broadly, the testing of enamelled winding wires can be classified into 5 types:
Testing based on Appearance & Dimension Parameters
If conductor diameter is not in range, resistance of customer’s product will not be ok and product will not perform as per requirement
If overall diameter is less, then electrical properties are compromised and customer may face problems of part failure, layer short, etc. If overall diameter is high, material may not fit into the space available with the customer for winding.
Roughness / Surface Defect
If there is a surface defect, then the insulation in that portion may be weak. If the roughness is of minor nature it may not impact the performance but if the roughness is high, it impacts the performance of the product. This is detected using 100x microscope. Naked eye tends to miss minor surface defects. These minor defects become larger when wire gets elongated after winding and hence it is important to look for defects with a digital microscope to ensure perfect inspection.
At Geekay, we produce wires with very fine tension controls with minimal stretching of product in the process <1%, SPC of >3 for conductor diameter. We strictly control the viscosity in process with temperature controlled enamel tanks and strict process control and ensure the use of PCD enamelling dies. The roughness is controlled & monitored through in line Pin Hole detectors.
Testing based on Electrical Parameters
Break down voltage
Every electrical product is supposed to withstand some voltage. Failure in BDV will impact performance and failure of the product on the field.
Continuity of covering – High voltage pin hole
Pin holes are leakages in the insulation from where current is leaking. If there are pin holes they will grow bigger during winding and if 2 pin holes are on top of each other, the coil will short circuit
Salt Water Bath Pin Hole
This Test checks for leakages in medium of water at low voltage. If there are pin holes, they will grow bigger during winding and if 2 pin holes are on top of each other, the coil will short circuit.
If conductor diameter is not in range or purity of raw material is not good, the resistance of the product will not be ok and product will not perform as per requirement.
A motor should perform consistently and for that the wire used must also be of consistent quality. In this the most challenging aspect is to maintain uniform concentricity of the enamel around the wire which gives it uniform electrical properties like pinhole and break down voltage. Testing the wire for this parameter is imperative to maintaining the wire quality and at geekay this is a part of our routine inspection as part of our endeavour to maintain consistent quality.
At Geekay, we use a special method of twisting and checking saltwater bath pin hole to simulate winding conditions. We use 100% virgin raw material to ensure conductor purity and source our enamel from reliable sources – Elantas, Fupao and Huber.
Also, as said earlier, at Geekay, the wires are produced with very fine tension controls with minimal stretching of product in the process <1%, SPC of >3 for conductor diameter. We strictly control the viscosity in the process with contact temperature enamel tanks and strict process control and ensure the use of PCD enamelling dies. The roughness is controlled & monitored through in-line Pin Hole detectors.
Testing based on Thermal Parameters
Heat Shock / Thermal Shock
Every motor or coil heats up when current passes through it. As per design, the wire is selected and if the wire cannot withstand the increase in temperature in the coil, the coil will burn during use.
Cut Through/ Softening Resistance
This is a thermo-mechanical test which indicates the temperature bearing capability of the wire.
This indicates the degree of curing of the wire. Every enamel has a recommended Tan Delta which is best suitable for wire properties.
At Geekay, we use 100% virgin raw material to ensure conductor purity and source our enamel from reliable sources – Elantas, Fupao and Huber. We follow a strict process control with Tan Delta being a critical aspect of measurement.
Testing based on Mechanical Parameters
Elongation, Springback, SEN
This indicates the softness of the wire. If this is NG, the customer may face problem of wire breakage during winding, coil not forming properly, hardness in the wire, etc
If the product has a space constraint, this is especially critical as a high Slip Value will lead to poor fill factor.
This indicates scratch resistance of the wire. Wire has tendency to get scratched by the various pulleys which it comes in contact with during winding. Low abrasion may mean that wire will get scratched during winding and coil will short circuit.
Flexibility / Jerk / Peel
This indicates the strength of adhesion of enamel to the wire. If this is poor, the enamel will peel off since the wire undergoes some stretching during winding.
At Geekay, we use special imported wax to lower slip value. Inline resistance annealing is used for bare wire to ensure uniformity of mechanical properties in pre-enamelling stage. We only use enamel from reliable sources – Elantas, Fupao and Huber and follow a strict process control with Tan Delta being a critical aspect of measurement. We use the best tan delta in the world from MAG & Ampac.
Testing based on Chemical Parameters
This test indicates the resistance of wire to certain solvents. This is primarily a property of raw material used, and hence may not be very critical test.
Refrigerant extraction test
With growing need of wire in the HVAC industry, the wire has to perform in the environment of various refrigerants and we need to test performance of wire in accelerated life tests in the presence of these chemicals. Hence at GEEKAY we now do refrigerant extraction test to meet this need of HVAC industry.
At Geekay, we use the right chemical raw material from the best sources in the world to ensure solvent resistance.
So these are some of the important testing parameters for enamelled winding wires or magnet wires. If you would like to learn more about the testing and quality parameters, we can organise a specially customised training webinar for your organisation. Learn more here