How to Choose a Magnet Charging Coil
Choosing the right magnet charging coil is not just about selecting a coil based on its size. The electrical, magnetic, mechanical, thermal, and environmental requirements should be verified before the production.
1. Calculate the Required Power
Calculate first the required input and output power. More required power may require larger winding, thicker wire, better heat dissipation, or a different structure of the coil.
2. Verify Operating Voltage and Current
Specify the operating voltage and the maximum current of the coil and the charging conditions. These parameters define the type of the conductor and electrical resistance.
3. Select the Proper Inductance
Inductance is one of the most important electrical parameters. The required inductance is defined by the charging circuit, operating frequency, compensation network, and power architecture.
4. Verify Operating Frequency
The coil must be compatible with the operating frequency of the system. The frequency affects the impedance, losses, magnetic coupling, heat dissipation, and charging efficiency.
5. Assess Coil Dimensions
“Be sure to calculate your available space for installation. Outer diameter, inner diameter, thickness, height, mounting surface, surrounding parts.”
6. Think Magnetic Alignment
If you use magnetic positioning, calculate the required magnetic force and alignment tolerance. Poor alignment may lead to less efficiency of charging.
7. Temperature Control
During operation the resistance of the coil causes the generation of heat. Consider the continuous operation conditions, duty cycle, ambient temperature, and temperature rise.
8. Choosing the Right Materials
The wire insulation, bobbin material, adhesives, magnetic materials, and protective components should be suitable for operating temperature and environment.
9. Think Mechanical Reliability
The coil should withstand vibrations, repeated charging cycles, assembly stress, and any other mechanical requirements.
10. Verify Capability of OEM Manufacturing
When choosing the supplier, evaluate the winding accuracy, testing capability, tooling capacity, quality control, sample support, and mass production capability.
A good selection includes electrical performance, charging efficiency, size, temperature, reliability, cost, and manufacturability.
How to avoid the most common magnet charging coil design mistakes
Here is a list of some of the common coil design mistakes to avoid.
1. Selecting the Coil Based on Its Physical Size
The coil can fit the product physically but fail in its electrical or power and thermal capabilities.
2. Ignoring the Operation Frequency
The coil should be designed based on the correct frequency of charging. Otherwise, you may get unexpected impedance and losses.
3. Underestimating the Temperature Rise
Heat is generated because of high current and resistance. Always check continuous duty and maximum environment temperature.
4. Poor Magnetic Alignment
If magnets are utilized for positioning, then you should account for mechanical tolerance. Excessive offset will decrease coupling.
5. Wrong Wire Diameter Selection
If the wire is too thin, it will generate excessive resistance and heat. If the wire is too thick, then it will be expensive and inflexible for the winding.
6. Overlooking the Metal around the Coil
Nearby metal parts can change the magnetic field and induce eddy current losses. Therefore, you should test the whole assembly.
7. Not testing in the assembled state
The coil may perform well without an assembly but fail in the final product. Thus, always test the whole mechanical and electrical assembly.
8. Not paying attention to production tolerances
To produce the coil uniformly, the coil resistance, inductance, dimensions, and winding tension should be within the tolerances.
9. Picking the Supplier Too Late
Do not wait till the end of the product development process. Include the supplier in your design.
