Method for controlling an induction coil, and induction coil apparatus

Patent metadata

Field	Value
Publication number	US-11855462-B2
Application number	US-202016802639-A
Country	US
Kind code	B2
Filing date	Feb 27, 2020
Priority date	Mar 5, 2019
Publication date	Dec 26, 2023
Grant date	Dec 26, 2023

Abstract

A method for controlling an induction coil on an induction hob involves a power generation for a primary power on the induction coil for power transmission to an electrical consumer put onto a cover above the induction coil, which consumer has a receiver coil and an electrical load connected thereto, being adjusted. The induction coil forms a primary-side resonant circuit with a capacitance connected in series, and the induction coil and the receiver coil are coupled in the style of a transformer such that a current in the induction coil induces a voltage in the receiver coil with a flow of current and generation of the secondary power in the load of the electrical consumer. The control means can attempt to adjust the desired secondary power to a steady state using maximum modulation of the voltage effectively applied to the primary-side resonant circuit, as second manipulated variable. The primary power is decreased in a first step by virtue of the voltage effectively applied to the primary-side resonant circuit, as second manipulated variable, being decreased before the operating frequency as first manipulated variable is increased in a second, subsequent step.

First claim

The invention claimed is:

1. Method for controlling an induction coil to adjust a power generation for a primary power on said induction coil, wherein:
said induction coil is designed for power transmission to an electrical consumer put onto a cover above said induction coil, said electrical consumer having a receiver coil and an electrical load connected to said receiver coil,
control means for said power generation are provided,
said induction coil forms a primary-side resonant circuit with a capacitance connected in series,
said induction coil and said receiver coil are coupled in a style of a transformer such that a current in said induction coil induces a voltage in said receiver coil that causes a flow of current and hence a generation of a secondary power in said load of said electrical consumer,
information pertaining to a desired secondary power on said load of said electrical consumer is prescribed for said control means of said induction coil,
said control means of said induction coil have at least two manipulated variables by means of which they alter said generated primary power, namely an altering of an operating frequency for said primary-side resonant circuit as a first manipulated variable and an altering of a voltage effectively applied to said primary-side resonant circuit as a second manipulated variable, the second manipulated variable being different than the first manipulated variable,
said control means of said induction coil operate with a transfer function P(f) that has at least one local peak and that, at least locally, is such that decreasing said operating frequency leads to said primary power being higher and increasing said operating frequency leads to said primary power being lower,
wherein
said control means in a first mode of operation always attempt to adjust a desired secondary power to a steady state using a maximum modulation of said voltage effectively applied to said primary-side resonant circuit, as the second manipulated variable, in the following cases:
in an event of a change in said desired secondary power or
in an event of a difference between a measured secondary power and said desired secondary power caused by a change in said transformer-style coupling between said induction coil and said receiver coil and/or by a change in said electrical load brought about by integrated switching means in said electrical consumer,
said primary power is increased by virtue of said control means decreasing said operating frequency as said first manipulated variable,
said primary power is decreased by virtue of two distinct steps, wherein said voltage effectively applied to said primary-side resonant circuit, as said second manipulated variable, is decreased in a first of the two distinct steps and said operating frequency as said first manipulated variable is increased in a second of the two distinct steps, the second step being subsequent to the first step.

2. Method according to claim 1 , wherein:
if said electrical consumer is moved and, as a result, said transformer-style coupling becomes lower and said primary-side resonant circuit is damped in a short time, said control means keep said primary-side current approximately constant at an initial level of said primary-side current of I_1 before said electrical consumer was moved, with a range of variation of ±5%, at constant operating frequency in a first step, wherein this is accomplished by reducing said voltage effectively applied to said primary-side resonant circuit, as said second manipulated variable, wherein this results in said secondary power being generated being lower than said desired secondary power,
said operating frequency as said first manipulated variable is then increased in a second step until said current in said induction coil has changed by no more than ±10% or said primary power differs from a value for said primary power at which said secondary power corresponds to said desired secondary power by no more than ±10%,
said voltage effectively applied to said primary-side resonant circuit, as the second manipulated variable, is subsequently altered again such that said primary-side current has again reached its initial level of I_1 before said electrical consumer was moved or said desired secondary power has been obtained,
said first aforementioned step and said second aforementioned step are then performed alternately until said measured secondary power is less than or equal to said desired secondary power or until a maximum possible voltage effectively applied to said primary-side resonant circuit, as said second manipulated variable, is reached.

3. Method according to claim 2 , wherein permanent operation of said induction coil to supply power to said electrical consumer is effected at an operating frequency at which a curve of the transfer function P(f) has a negative first derivative over said operating frequency.

4. Method according to claim 1 , wherein in said second step, when said operating frequency as said first manipulated variable is increased, a threshold for a change in said current in said induction coil or a threshold for a change in said primary power upward is lower than downward.

5. Method according to claim 1 , wherein information pertaining to a desired secondary power on said load of said electrical consumer is prescribed for said control means.

6. Method according to claim 5 , wherein said electrical consumer sends said prescribed value for said power generation to said power generation.

7. Method according to claim 1 , wherein said power transmission is permanently effected at said maximum possible voltage effectively applied to said primary-side resonant circuit, as said second manipulated variable, wherein an effective voltage of maximum magnitude is applied to said induction coil at an arising operating frequency as said first manipulated variable.

8. Method according to claim 1 , wherein said increasing of said operating frequency is stopped each time as soon as a resulting change in said primary power reaches a threshold of +/−10%.

9. Method according to claim 1 , wherein multiple induction coils in an induction hob are controlled using said method, wherein an operating frequency to increase said primary power of one of said induction coils is not reduced continuously but is reduced in steps or stages.

10. Method according to claim 9 , wherein a change in said operating frequency of one said induction coils is synchronized together with those changes of said operating frequency of other said induction coils.

11. Method according to claim 1 , wherein an operating frequency is used that is above said operating frequency at which said transfer function P(f) has its local peak.

12. Induction coil apparatus having at least one induction coil designed for power transmission to an electrical consumer put onto a cover above said induction coil, which electrical consumer has a receiver coil and an electrical load connected thereto, wherein said induction coil apparatus:
has control means for a power generation for a primary power on said induction coil,
has a capacitance that is connected in series with said induction coil and forms a primary-side resonant circuit,
has a controller designed to perform the method according to claim 1 , wherein:
said induction coil and said receiver coil are coupled in the style of a transformer such that a current in said induction coil induces a voltage in said receiver coil that causes a flow of current and hence a generation of a secondary power in said load of said electrical consumer,
said control means of said induction coil have at least two manipulated variables by means of which they alter said gen

Assignees

• Ego Elektro Geraetebau Gmbh

Inventors

• Egenter Christian
• Goebel Robin
• Herweg Elmar

Classifications

• H02J50/12 Primary

  of the resonant type · CPC title

• A47J43/0465

  with magnetic drive · CPC title

• H02J50/10

  using inductive coupling · CPC title

• H02P13/00

  Arrangements for controlling transformers, reactors or choke coils, for the purpose of obtaining a desired output · CPC title

• H05B6/06 Primary

  Control, e.g. of temperature, of power · CPC title