EMC compliant electric heating technology with integrated control in combination with a frequency converter

Abstract

EMC compliant electric heating technology with integrated control in combination with a frequency converter.

Description

2. Description of the invention

[0001] This description presents a new configuration for controlling an electric heating system with the associated components such as water tank and heating element, in which the heating elements are supplied with energy via a frequency converter in order to increase the efficiency of the electric heating.

[0002] The use of a frequency converter in residential areas requires compliance with EMC guidelines. The following sections explain the required components and the heating control system, which is EMC-compliant and enables optimal system integration through targeted parameter settings. This can save energy during the heating process.

[0003] In combination with a photovoltaic system, the heating technology can be operated in a significantly more energy-efficient manner in order to reduce costs. 3. Technical field of the invention and areas of application

[0004] The present invention relates to an electrical frequency-controlled heating device for heating interior spaces, in particular to a compact and low-maintenance solution characterized by high reliability and easy installation. 4. Objectives and technical tasks4.1 Objectives • The aim of the invention is to provide an electric heater which uses the thermal inertia of the heating element through frequency-controlled control of the heating power in order to achieve the desired temperature difference (ΔT) with minimal energy consumption. • Ensure EMC compliance of a frequency converter when used with resistive loads in residential areas. • Putting together a heater with just a few components that need to be installed. • Generate the highest possible efficiency from an electric heater by eliminating all losses and achieving the best possible control and regulation of the heater. • Completion of a mini heating circuit to circulate the water in the shortest possible distance so that all the water in the water tank is brought to the same temperature. 4.2 Technical tasks • Determination of the frequency ranges for the switching on and off ramps. • Determination of all components in compliance with the required technical values. • Control of the frequency converter / heating according to summer and winter function. • Control of the frequency converter / heating with night-time reduction and holiday mode. • Opening and closing of the flow and return lines in different operating modes • Writing a PLC program for all processes such as automatic operation. • Development of a control cabinet with 2 chambers for the heating control, with the control electronics separated from the power electronics to ensure EMC compliance. 5. State of the art and remedy of defects

[0005] Modern heating systems such as heat pumps, gas heaters, or district heating offer different approaches to heat generation. Heat pumps utilize ambient heat and are particularly energy-efficient, but require complex technology and high investment costs. Gas heaters are powerful but dependent on fossil fuels. District heating requires a centralized infrastructure. Conventional electric heating systems usually operate with rigid on / off control, which can result in energy losses due to overheating or unnecessary peak loads. Modern control technologies such as frequency converters have so far been used primarily in drive systems, but also offer potential for increasing efficiency in electric heating. Frequency converters generate high field and cable-side emissions as well as harmonics, which make their use in residential areas impossible. Solution

[0006] Controlling a heating element via a frequency converter requires the combination of additional components such as a line filter and a DC link choke. Furthermore, ferrite cores and spatial separation of the cables and components are necessary at relevant points in the control system to ensure EMC compliance. Direct control of the heating element exclusively via the frequency converter is not permitted, as the emission limits can only be met in industrial areas, not in residential environments. To meet the limits in residential areas, both the selection of the components to be installed and the system design are crucial. In this invention, the corresponding requirements were implemented in such a way that EMC compliance is ensured through the targeted combination of components and the structural design of the system.This means that all the advantages of a frequency converter can also be used in the living area to make heating control as efficient as possible.

[0007] The heating device according to the invention comprises an electric heating element controlled by a frequency converter. The frequency converter's on and off ramps are programmed to smoothly increase and decrease the heating output. This ensures optimal use of the stored heat in the heating element without causing unnecessary energy losses due to abrupt switching on or off. The inertia of the heating element—that is, its ability to store and release heat over short periods of time—is used specifically to achieve the required ΔT in the room before energy needs to be added again.

[0008] Smooth ramp control via the frequency converter avoids peak loads and increases component lifespan. At the same time, energy efficiency is increased because the stored heat in the heating element is utilized between heating cycles. Compared to traditional on / off controls, energy consumption is measurably reduced without compromising comfort. 6. State of the art with the heating and water heating technology described here

[0009] Advantages of the heating according to the invention • Minimal design: The heating device consists of only two main components – a heating element and a control unit with an integrated frequency converter, as well as components that ensure EMC compliance for residential areas. This significantly reduces complexity and potential sources of error. • Easy installation: Thanks to its modular design, the heater can be installed with minimal effort. The components are preconfigured and only require the supply and return lines, cold and hot water connections, and an electrical connection, which can be single-phase or three-phase. • Compact design: The small number of components enables space-saving installation, ideal for retrofitting or tight installation situations. • Low maintenance: Fewer components mean fewer wear parts. The heater is virtually maintenance-free and extremely durable. • Cost-effective: The reduced design reduces production, storage, and installation costs. At the same time, the intelligent and EMC-compliant control via the frequency converter saves energy. • Quick commissioning: Thanks to preconfigured controls and simple connection options, the heater is ready for use immediately - ideal for temporary or mobile applications. 6.1 Why is the heating and water heating technology described here more efficient than other heating systems?

[0010] The innovative electric heater described here combines state-of-the-art control technology with maximum user-friendliness. Designed for maximum efficiency and individual customization, it offers a reliable solution for hot water and space heating – year-round and EMC-compliant.

[0011] Description of heating operation with frequency ramp and energy optimization. The heating system according to the invention uses an intelligently controlled frequency converter to ensure efficient and EMC-compliant heating operation. The operating sequence is as follows: • Smooth ramp: When the heater is switched on, the inverter's output frequency is gradually increased (the voltage and current—heating power—increase with frequency). This ramp prevents electromagnetic interference and reduces the inrush current. At the same time, the frequency is increased above 50 Hz to create a short-term boost effect that temporarily increases the heating power and enables a faster temperature rise. • Energy-optimized shutdown process: When switching off, the frequency is also gently reduced over a longer ramp. This specifically utilizes the thermal inertia of the heating element: The stored thermal energy in the heating element is sufficient to reach the target temperature, even if the frequency converter has already reduced the power supply. • Temperature dynamics and savings: With a temperature difference (ΔT) of, for example, 10 °C, the target temperature can be reached even though the frequency converter reduces the frequency and thus the energy supply early. This leads to noticeable energy savings during both startup and shutdown. Internal short heating circuit in summer operation

[0012] During summer operation, the main heating circuit of the heating system is deactivated – the flow and return lines to the heating system are closed. Hot water is generated exclusively via the integrated boiler.

[0013] To efficiently heat the entire water volume in the storage tank, an internal short heating circuit is activated. This consists of a short hydraulic connection between the outlet and the lower section of the water tank. The heated water is immediately returned to the lower section of the storage tank via an internal circulation pump.

[0014] Thanks to the minimal hydraulic distance and targeted circulation, the heated water is distributed quickly and evenly throughout the storage tank. Natural convection, which normally leads to temperature stratification (warm water at the top, cold water at the bottom), is eliminated by the forced circulation. This results in a homogeneous temperature distribution throughout the entire storage tank.

[0015] Heating is achieved indirectly via a heat exchanger coil integrated into the boiler, which heats the domestic water through heat transfer. The internal heating circuit ensures that the heat energy is distributed efficiently and evenly throughout the storage tank, quickly reaching the target temperature throughout the entire volume. 6.2 Special features of heating and water heating technologyTechnical equipment • Frequency converter control: Enables precise control of the heating output in all operating conditions. • Water storage tank with integrated coil: Efficient heat transfer for domestic water preparation. • Heating element: Generously dimensioned, robust and durable - designed for high thermal loads. • Temperature safety limiter: Protection against overheating and system failure. Ease of use • Intuitive menu navigation: Clear, generously designed display for easy navigation. • App control: Alternative operation via mobile devices for maximum flexibility. • Fine adjustment: Users can individually adjust the heating output in all operating modes (summer and winter) - e.g. according to the size of the living space or the number of people. Operating modes & functions • Summer / winter function: Automatic or manual switching depending on the outside temperature. • Day / night shutdown: Energy-optimized operation through time-controlled heating phases. • Vacation mode: Minimizes energy consumption during extended absences. • Outside temperature sensor: Dynamic adjustment of the heating output to the ambient temperature. Installation & Assembly • Pre-assembled components: All components are pre-assembled - only hydraulic and electrical connections are required. • Very easy to install: Ideal for quick installation without special tools. 7. Description of the system functionsCompact control cabinet with two-chamber system

[0016] The heating system has a specially developed control cabinet with two separate functional chambers: • Chamber 1 - Control electronics Contains all components for control and monitoring: ◯ Temperature sensor ◯ Circulation pump control ◯ HMI display (user interface) ◯ Communication interfaces and sensors • Chamber 2 - Power Electronics Contains the frequency converter and power components. The physical separation from the control electronics serves to ensure thermal decoupling and EMC optimization. EMC-compliant equipment

[0017] The following components are integrated to ensure compliance with electromagnetic compatibility (EMC): • Line filter dampens line-borne interference. • DC link choke Reduces harmonics and smooths current curves in the DC link of the frequency converter. • Ferrite cores Strategically placed ferrites on cable entry points filter high-frequency emissions and prevent interference. Cable routing & EMC separation

[0018] The cable routing is specifically designed for EMC isolation and functionality: • Supply line is from the top of the control cabinet - separate from power cables. • Supply cables to the heating elements are routed from the bottom side to ensure spatial separation. • Cable types The heating element is supplied via shielded power cables, dimensioned according to the heating power. This prevents crosstalk and minimizes field-side emissions. Description of the heating boiler Structure & connections

[0019] The boiler is designed so that the connections are optimally arranged for heat flow and hydraulic separation: • Lower level (same height, offset laterally): ◯ Heating return - returns the cooled heating water to the boiler. ◯ Cold water inlet - Fresh water supply for domestic hot water heating. • Upper level (same height, offset laterally): ◯ Heating flow - draws the heated heating water for the heating circuit. ◯ Hot water outlet - draws off the heated drinking water. Heat exchanger principle • A spiral is installed inside the boiler which is connected to the fresh water connections. • The spiral utilizes the maximum vertical length of the boiler, which: ◯ The cold water stays in the heat exchanger longer. ◯ More efficient heat transfer takes place. ◯ The set flow temperature is achieved more precisely than with conventional systems. Temperature measurement • A temperature sensor is placed centrally in the middle of the boiler. • This enables a representative average measurement of the water temperature in the storage tank. Insulation & Energy Efficiency • The boiler is designed in the best insulation class. • A-class boilers with approx. 50 mm insulation are usually used. • In this system the insulation is even thicker, which: ◯ Heat losses are further minimized. ◯ Significantly increases energy efficiency. ◯ Improved temperature stability over longer periods. Description of the heating element

[0020] The heating element is specially designed for higher frequencies and thermal loads. Its construction enables reliable and long-lasting operation even under demanding operating conditions. Technical features • Frequency-optimized The heating element exhibits stable and even heat development even at frequencies above 50 Hz. The higher load capacity at higher frequencies is a clear advantage: ◯ The controlled increase in heating output can be easily accommodated ◯ No overload or material fatigue during dynamic power adjustment • Load-optimized dimensioning. The specific load per square centimeter of heating surface is significantly lower than the market standard. This leads to: ◯ Lower thermal stress ◯ Extended service life ◯ Minimized risk of hotspots • Efficient heat transfer The reduced surface load ensures even heat dissipation and improves the energy efficiency of the system. 8. Example of summer operation with bypass function

[0021] In summer mode, the space heating is deactivated. The electric ball valves on the heating flow and return lines close automatically. At the same time, the electric ball valve in the bypass opens, activating a small internal circulation circuit. • The water circulates exclusively directly at the boiler. • The heating works with a heating interval of 10 °C ΔT, for example. • The frequency converter controls the heating output dynamically: ◯ Smooth start-up with frequency > 50 Hz for fast heat boost ◯ Early power reduction by utilizing the heating element inertia Advantages: • The target temperature is reached faster than with conventional mains operation. • Energy consumption is reduced through optimized frequency parameters. • The entire boiler water is brought to a uniform temperature. • The coil in the boiler works more efficiently because the surrounding water is warmer. • Hotter water is available at the hot water outlet. • Less hot water has to be drawn off by the consumer → lower flow rate. • The next heating interval is delayed → fewer daily heating cycles. Winter operation with heating circuit

[0022] During winter operation, the electric ball valves on the heating flow and return lines open. The electric ball valve in the bypass closes. The water now circulates throughout the entire heating circuit. • The heating output is also frequency controlled. • The system demonstrates superior efficiency compared to conventional heating technologies, particularly in the upper temperature ranges. • The dynamic adjustment of the heating output ensures even heat distribution and minimizes energy losses. • The on and off delays (ramps) can be individually parameterized for summer and winter operation to ensure optimal thermal control and energy efficiency of the heating system. Adaptive control via the frequency converter enables precise power adjustment to the respective operating state, thus offering significant advantages in terms of control quality and energy savings. Thanks to the EMC-compliant design of the entire system—including suitable filter components, ferrite cores, and wired decoupling—the use of this technology is now also permitted in sensitive residential environments. Energy consumption of the heating system - summer vs. winterTechnical basis • Heating output: 12 kW • 1 kWh = 1 hour of operation with 1 kW • Summer operation Usage scenario Heating intervals / day Duration per interval Energy consumption / day Without showers 1 3 minutes 12 kW × 0.05 h = 0.6 kWh With showers up to 4 3 minutes 12 kW × 0.2 h = 2.4 kWh • Winter operation Heating intervals / day Duration per interval Energy consumption / day 6 10 minutes 12 kW × 1h = 12 kWh 12 10 minutes 12 kW × 2 h = 24 kWh • Comparison of summer vs. winter Period Minimum consumption Maximum consumption Summer 0.6 kWh / day 2.4 kWh / day winter 12 kWh / day 24 kWh / day

[0023] In this example, the figures are conservative. In summer operation, energy consumption is up to 40 times lower than in winter operation. The short heating duration (3 minutes) combined with high efficiency saves massive amounts of energy. Intelligent interval control reduces unnecessary heating cycles. In winter, consumption increases significantly due to longer intervals and larger circulation circuits. Conclusion

[0024] The heating system described represents an innovative solution for energy-efficient hot water production, which offers significant advantages over conventional systems in both summer and winter operation.

[0025] In summer operation, the intelligent bypass function enables circulation in the smallest circuit, allowing the heater to reach the desired hot water temperature with minimal energy consumption (0.6-2.4 kWh / day). The use of a frequency converter to control the heating output allows for precise and rapid heating with short heating intervals (3 minutes), significantly reducing daily heating cycles.

[0026] During winter operation, full heating circuit circulation is activated. Despite higher energy requirements (12-24 kWh / day), the system demonstrates superior efficiency thanks to its frequency-controlled control, especially in the upper temperature ranges. The combination of targeted circulation, dynamic power control, and efficient heat transfer ensures optimized energy utilization and minimizes heat loss.

[0027] Particularly noteworthy is the first-ever implementation of an EMC-compliant design for resistive loads. This technical implementation ensures the system's electromagnetic compatibility even when directly controlling heating resistors, something that was previously impossible. This increases immunity to mains interference and ensures compliance with international EMC guidelines – a crucial step for industrial and building services applications.

[0028] The technical design offers a significant improvement over existing heating technologies and meets the requirements for sustainable, resource-efficient building technology. The clear separation and control of operating modes, the documented consumption values, and the EMC-compliant construction demonstrate the level of innovation and practical relevance of the solution. List of reference symbols

[0029] Fig. 1 - Main system diagram

[0030] This figure shows the simplified connection diagram of the heating system. Designation of the numbers from Figure 1 : 1 supply line 2 Upper part of the control cabinet - 1. Chamber with the control electronics 3 HMI display operator interface 4 Lower part of the control cabinet - 2nd chamber with the power electronics such as frequency converter, DC link choke and line filter 5 mains filters 6 frequency converters 7 DC link choke 8 Supply cable from heating element 9 Cold water inlet 10 Temperature sensor 11 Hot water outlet 12 Circulation pump 13 Electric ball valve heating flow (controlled via the control electronics) 14 Heating flow 15 Electric ball valve bypass (controlled via the control electronics) 16 Coil in the boiler for hot water 17 Insulation of the boiler 18 Electric ball valve heating return (controlled via the control electronics) 19 Heating return 20 Internal short heating circuit Character list • Fig. 1 - Main system diagram

Claims

[1] EMC compliant electric heating technology with integrated control in combination with a frequency converter. [2] EMC-compliant electric heating technology with integrated control in combination with a frequency converter, according to claim 1, characterized by , that the supply of the resistive load, in particular a heating element, is provided via a frequency converter, wherein the system for compliance with electromagnetic compatibility (EMC) comprises the following components in combination: a frequency converter, a mains filter, a DC link choke and ferrite cores. [3] EMC-compliant electric heating technology with integrated control in combination with a frequency converter, according to claims 1 and 2, characterized by, that the control cabinet is designed as a two-chamber system, with the control electronics and the power electronics being spatially separated to minimize electromagnetic interference and improve the EMC compliance of the overall system. [4] EMC-compliant electric heating technology with integrated control in combination with a frequency converter, according to claims 1, 2 and 3 characterized by , that the frequency converter is operated with a switch-on ramp and a switch-off ramp when operating resistive loads, in particular a heating element, whereby the thermal inertia of the heating element is specifically used to bring the water to the desired temperature with reduced energy input. [5] EMC-compliant electric heating technology with integrated control in combination with a frequency converter, according to claims 1, 2, 3 and 4 characterized by, that the EMC-compliant control of the resistive loads via a frequency converter is used in the operation of heating systems, whereby the control is designed in such a way that electromagnetic interference is minimized and the energy efficiency of the system is improved. [6] EMC-compliant electric heating technology with integrated control in combination with a frequency converter, according to claims 1, 2, 3, 4 and 5 characterized by , that the integrated control for EMC-compliant control of the resistive loads is optionally designed as single-phase or three-phase, depending on the respective mains supply and power requirement of the heating system. [7] EMC-compliant electric heating technology with integrated control in combination with a frequency converter, according to claims 1, 2, 3, 4, 5 and 6 characterized bythat the integrated control is carried out via a human-machine interface (HMI) and / or a mobile application (app), whereby the user has the following setting options available on the frequency converter-guided control: • Flow and return temperature • Temperature difference (Delta-T) • Day and night reduction • Holiday mode • Switching between automatic and manual operation • Control via outdoor temperature sensor • Regulation of heating output • Summer and winter function • Reading out consumption data and operating histories • Setting of switch-on and switch-off ramps • Setting the output frequency of the frequency converter [8] EMC-compliant electric heating technology with integrated control in combination with a frequency converter, according to claims 1, 2, 3, 4, 5, 6 and 7 characterized by, that an internal, short heating circuit (bypass) is integrated at the water storage tank between the heating flow and return, which opens and closes automatically via the heating control depending on the operating mode (summer or winter operation). [9] EMC-compliant electric heating technology with integrated control in combination with a frequency converter, according to claims 1, 2, 3, 4, 5, 6, 7 and 8 characterized by , that the heating power is increased by increasing the output frequency of the frequency converter above 50 Hz, thereby enabling faster heating of the water. [10] EMC-compliant electric heating technology with integrated control in combination with a frequency converter, according to claims 1, 2, 3, 4, 5, 6, 7, 8 and 9 characterized by, that the integrated control of the heating system is operated in combination with a photovoltaic system, whereby the electrical energy generated by solar energy is used to supply the heating system.

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