How to improve the efficiency of sensor for medium frequency induction heating machine

The inductor is an important part of the medium frequency induction heating machine and is necessary for the heat treatment of the workpiece. Therefore, it is of great practical significance to understand how to improve the efficiency of sensors.

The ways to improve the sensor efficiency of medium frequency induction heating machines are as follows:

1. Correctly select the current frequency

Correctly selecting the current frequency according to the diameter or thickness of the workpiece is the fundamental guarantee for improving the efficiency of the sensor. The ratio of workpiece diameter (or thickness) to current penetration depth determines electrical efficiency.

When designing the sensor, care should be taken that the electrical efficiency should not be less than 80%. When the electrical efficiency is too low, measures such as transverse magnetic flux heating sensors should be used to improve the electrical efficiency.

2. Use rectangular tubes instead of round tubes

The current distribution in the cross-section of a rectangular tube is different from that of a circular tube. When the gap is the same, rectangular tubes are 10% more efficient than circular tubes.

3. Reasonably allocate the conductive length of each part of the sensor

Each inductor consists of two parts, namely the conductive plate and the effective coil. The voltage on the inductor must be distributed between the conductive plate and the effective coil. Their resistance is very small (compared with their own inductive reactance). The distribution of voltage basically depends on the inductive reactance. The larger the inductive reactance, the more voltage is distributed. Therefore, the greater the ratio of the unfolded length of the effective coil to the length of the conductive plate, the more power can be distributed to the effective coil. Therefore, when the length of the conductive plate is long, a multi-turn inductor should be used to increase the effective coil expansion length. However, excessively increasing the number of turns will destroy the matching between the load and the oscillation loop, so the number of turns must be moderate, and this should also be noted.

4. Reduce the contact resistance of the sensor connection surface

There is contact resistance between the inductor contact plate and the quenching transformer joint, and between the opening and closing surfaces of the opening and closing inductor. Its size is related to factors such as contact pressure, contact form, contact area, and contact material. The greater the contact pressure and the larger the contact area, the smaller the contact resistance. Therefore, the sensor contact surface is required to have good surface roughness and a certain contact pressure. When the contact pressure is lower than the critical value, the contact resistance increases, leading to a vicious cycle of heating, oxidation, and further increase in contact resistance at the contact surface. Therefore, the pressure layout of the contact surface should be reasonably designed.

5. Use magnetic conductors

When heating the inner hole or flat surface of the workpiece, its efficiency is lower than that of outer circle heating. After the effective ring straddles the magnetic conductor, the heating efficiency is improved.