A new frequency, phase and control technology of electromagnetic heater

background:

At present, electromagnetic induction heating technology has been widely used in plastic machinery, food machinery, crude oil heating and transportation, chemical machinery and other heating industries. Compared with traditional resistance wire heating technology, electromagnetic induction heating equipment has the characteristics of fast heating speed, high thermal efficiency, significant energy saving effect, and is simple to use and convenient to maintain. However, the industrial electromagnetic induction heaters on the market currently generally have the problem that the heater board is easy to burn out and the power is unstable, which leads to a decrease in the confidence of the heating industry transformation. This article mainly proposes a series of novel and practical solutions from a technical point of view to the problems existing in the current electromagnetic induction heating technology, including frequency and phase tracking, power adaptation and other technologies.

Content:

The purpose of this invention is to solve the technical problems of easy burning and unstable power of electromagnetic heaters currently on the market. It is mainly divided into the following parts

1. Frequency and phase tracking technology

At present, the frequency and phase tracking of electromagnetic heating products can be mainly divided into two categories; one is to rely on pure hardware phase-locked loop implementation, and the system block diagram is as follows:


This type of method has a simple structure, but the phase-locked loop cannot achieve cycle-by-cycle phase detection, and is easily interfered with and cannot lock the frequency, resulting in burning. The power output is also affected by the input power supply, and constant power output cannot be achieved.

The second type relies on a high-performance processor to achieve frequency and phase tracking. The system block diagram is as follows:


This circuit uses a preprocessing circuit to preprocess the output current and voltage phase. When the frequency and phase are not locked, the output is high level, and when locked, the output is low level. It can realize cycle-by-cycle phase detection, which provides conditions for the circuit to achieve high reliability. The microprocessor calculates according to the high and low pulse signals, controls the oscillator, and realizes frequency and phase tracking. Due to the preprocessing of the output current and voltage phase, the workload of the microprocessor is reduced, so that low-performance microprocessors can also do the job, greatly reducing costs.

The system block diagram is as follows:



The following is a technical verification module:

using transformer isolation to drive IGBT, it can be used in a 5KW half-bridge heating circuit!


During normal operation, UCE-current waveform:


Before powering on, the coil is forced to short-circuit, and the protection process waveform after powering on: the red curve is the enable pin of the driver chip, and the blue curve is the drive waveform.

When working, the coil forced short circuit protection process waveform: the red curve is the driver chip enable pin, and the blue curve is the drive waveform.


The current tested working frequency is 43KHz, and the goal is above 300KHz, so that copper and aluminum can be heated. Please support us!