Frequent heating of micro solenoid coils is a common problem, and the following are some possible solutions:
I. Analyze the cause of fever
1. Excessive current
When the current passing through an solenoid coil exceeds its rated current, the resistance of the coil will generate excessive heat according to Joule’s law. This may be due to the high power supply voltage, resulting in an increase in the current calculated according to Ohm’s law. For example, if the rated voltage of the solenoid coil is 5V and the resistance is 10 Ω, the normal operating current should be 0.5A. But if the power supply voltage rises to 10V, the current will become 1A and the heating power will increase by four times.
2. The issue of coil turns
Too few turns may result in insufficient inductance. In AC circuits, inductance has a hindering effect on current. If the number of turns is small and the inductance is small, the obstruction effect on AC current is small, and the current is prone to overheating due to excessive current.
3. Iron core issue
If the solenoid coil has an iron core, the material and working state of the iron core will also affect the heating of the coil. For example, if the iron core is a material with high magnetic permeability but prone to hysteresis loss, under the action of the alternating magnetic field, the magnetic domains inside the iron core will flip repeatedly, generating heat and causing the coil to heat up. In addition, if there is a short-circuit ring damage to the iron core (for AC solenoid coils), it will increase the eddy current loss in the iron core and also cause the coil to heat up.
4. Poor heat dissipation conditions
If the working environment of the micro solenoid coil is poorly ventilated or its own heat dissipation structure design is unreasonable, the heat will be difficult to dissipate. For example, if a coil is enclosed in a narrow plastic casing without ventilation holes, heat will accumulate inside.
II. Treatment of causes
1. Control current
Adjust power supply voltage: If the current is too high due to high power supply voltage, a voltage regulator can be used to stabilize the voltage. For example, connecting the power supply line of the solenoid coil to a linear regulator or switching regulator that stabilizes the output voltage at the rated value to ensure that its operating voltage meets the requirements.
Adjust power supply voltage: If the current is too high due to high power supply voltage, a voltage regulator can be used to stabilize the voltage. For example, connecting the power supply line of the solenoid coil to a linear regulator or switching regulator that stabilizes the output voltage at the rated value to ensure that its operating voltage meets the requirements.
Series resistor: If possible, a suitable resistor can be connected in series to reduce the current passing through the coil. Calculate the required resistance based on Ohm’s law. However, it should be noted that series resistance may cause some electrical energy to be lost on the resistance and may affect the performance of the solenoid coil, which needs to be considered comprehensively.
2. Optimize the number of coil turns
If the heating is caused by a problem with the number of turns, the coil turns can be redesigned. This requires calculating the appropriate number of turns based on the specific application and solenoid principles of the solenoid coil. For simple DC solenoid coils, the inductance can be increased by increasing the number of turns, thereby controlling the current to a certain extent. But for AC solenoid coils, changes in the number of turns can also affect multiple parameters such as inductance, requiring more complex calculations and adjustments.
3. Improve the condition of the iron core
Replace the iron core material: If the hysteresis loss of the iron core is the main cause of heat generation, you can choose an iron core material with lower hysteresis loss. For example, the ordinary silicon steel core is replaced with high-performance soft magnetic materials such as iron-nickel alloy. These materials have narrow hysteresis loops and small hysteresis losses.
Check and repair the iron core short-circuit ring: For AC solenoid coils, it is necessary to check whether the iron core short-circuit ring is intact. If the short-circuit ring is damaged, it needs to be repaired or replaced in a timely manner. It can be determined by observing whether the short-circuit ring is broken or loose. When repairing, welding or other methods can be used to connect the broken parts.
4. Enhance heat dissipation capability
Improving ventilation conditions: If the heating is caused by poor ventilation, ventilation holes can be added near the installation location of the solenoid coil, or auxiliary heat dissipation devices such as fans can be used. For example, in a closed electrical control cabinet, a small axial fan is installed to circulate air and remove the heat generated by the coils.
Using heat dissipation materials: Thermal conductive silicone grease can be applied to the surface of the solenoid coil, and then heat dissipation fins can be installed. Thermal conductive silicone grease can fill the small gaps between coils and heat sinks, improving thermal conductivity efficiency. Heat sinks can increase the heat dissipation area and dissipate heat to the surrounding environment more quickly.
