Omar Khalid
The dissipation factor (DF or tan δ) is a crucial property of plastics that directly impacts their performance in electrical and electronic applications. It is a dimensionless measure defined as the ratio of the power dissipated in a material to the power applied to it, indicating the inefficiency of the material to hold energy or act as an insulator. In other words, it represents the loss rate of energy in a mode of oscillation within a dissipative system. Most plastics exhibit relatively low dissipation factors at room temperature, making them suitable for high-frequency applications such as radar equipment or microwave parts. The dissipation factor is also an important consideration in capacitor design, as it influences signal integrity, energy efficiency, and heat generation.
| Characteristics | Values |
|---|---|
| Definition | The dissipation factor (DF) is a measure of the loss-rate of energy of a mode of oscillation (mechanical, electrical, or electromechanical) in a dissipative system. |
| Other names | Dielectric loss factor, loss factor, tan δ |
| Formula | The ratio of the ESR to the capacitive reactance XC, or the reciprocal of the ratio between the insulating materials' capacitive reactance to its resistance (ESR) at a specified frequency. |
| Frequency dependency | The dissipation factor is frequency-dependent, and polarization losses and capacitance vary with frequency. |
| Temperature dependency | The dissipation factor is temperature-dependent. |
| Unit | The dissipation factor is a dimensionless measure and hence has no units. |
| High/low values | A low dissipation factor indicates high-quality, high-performance electrical or electronic systems. |
| Dielectric constant relationship | The dissipation factor is the product of the dielectric constant and the dissipation factor. |
| Electrical circuits | When representing electrical circuit parameters as vectors in a complex plane, known as phasors, a capacitor's dissipation factor is equal to the tangent of the angle between the capacitor's impedance vector and the negative reactive axis. |
| Capacitors | The dissipation factor due to a non-ideal capacitor is expressed as the ratio of the resistive power loss in the ESR to the reactive power oscillating in the capacitor. |
| Quality factor | The dissipation factor is the reciprocal of the quality factor, which represents the "quality" or durability of oscillation. |
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What You'll Learn
Dielectric constant and dissipation factor
The dissipation factor (DF) is an electrical property of plastics and other insulating materials. It measures the electrical energy absorbed and subsequently lost when an electrical current is applied to an insulating material. The DF is defined as the reciprocal of the ratio between the insulating material's capacitive reactance and its resistance (Equivalent Series Resistance or ESR) at a specified frequency. The lower the DF, the more efficient the insulator system.
The DF is also referred to as the tangent of the loss angle, loss tangent, tan delta, or power factor. It is a dimensionless measure and has no units. The DF increases with increases in temperature and humidity. This increase is often dramatic and can even be destructive at the glass transition temperature of plastics.
The dielectric constant, also known as the relative permittivity, is used to determine an insulator's ability to store electrical energy. It is the ratio of the capacitance induced by two metallic plates with an insulator between them to the capacitance of the same plates with air or a vacuum between them. The dielectric constant can be measured using a HP 4284A LCR meter with a HP 1645B test fixture. The frequency range for this measurement is 20 Hz to 1 MHz.
The dielectric loss factor or loss factor of a material is another frequently used term. It is the product of the dielectric constant and the dissipation factor. It is related to the total loss of power occurring in plastics or any other insulating materials. It indicates how easily the material will heat up in a high-frequency field.
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Capacitors and ESR
The dissipation factor (DF or tan δ) is an electrical property of plastics and other insulating materials. It is defined as the reciprocal of the ratio between the insulating material's capacitive reactance and its resistance (Equivalent Series Resistance or ESR) at a specified frequency. In other words, it is the ratio between the permittivity and the conductivity of the material. A low dissipation factor indicates a high-quality, high-performance electrical or electronic system.
ESR is an important consideration in the selection of electrolytic capacitors. It is the series resistive effects of a capacitor combined into a single element. ESR is frequency-dependent, temperature-dependent, and changes as components age. At high frequencies, there are losses in the windings due to proximity and skin effects, which lead to a higher ESR. In a non-electrolytic capacitor and electrolytic capacitors with solid electrolytes, the metallic resistance of the leads and electrodes, and losses in the dielectric cause the ESR.
Polymer capacitors usually have lower ESR than wet-electrolytic capacitors of the same value, and they are stable under varying temperatures. Therefore, they can handle higher ripple currents. Aluminium and tantalum electrolytic capacitors with non-solid electrolytes have much higher ESR values, up to several ohms. ESR decreases with frequency up to the capacitor's self-resonant frequency.
ESR can increase enough to cause circuit malfunction and component damage, although the measured capacitance may remain within tolerance. This can be caused by normal aging, high temperatures, and large ripple currents. In a circuit with a significant ripple current, an increase in ESR will increase heat accumulation, accelerating aging. Electrolytic capacitors rated for high-temperature operation and of higher quality are less susceptible to premature failure due to ESR increase.
Some capacitors are designed specifically for low-ESR, but manufacturers of aluminium electrolytic capacitors do not specify ESR consistently. For capacitors of comparable size and CV, a device with higher capacitance and a lower voltage rating will have a lower ESR.
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Electrical applications
The dissipation factor (DF or tan δ) is an important electrical property of plastics and other electrical insulating materials. It is defined as the reciprocal of the ratio between the insulating material's capacitive reactance to its resistance (Equivalent Series Resistance or ESR) at a specified frequency. In other words, it is a ratio between the permittivity and the conductivity of an electrical insulating material.
The dissipation factor is a critical consideration in electrical applications, especially when designing high-frequency circuits, capacitors, insulators, or RF components. It directly impacts signal integrity, energy efficiency, and heat generation in these components.
For instance, in the case of plastic insulators used in high-frequency applications such as radar equipment or microwave parts, a low dissipation factor is desirable. This indicates superior electrical performance, minimal energy loss, and reduced dielectric heating. On the other hand, for polymers that need to be heated in a radio frequency or microwave oven for welding or drying, a high dissipation factor is required.
The dissipation factor also plays a role in assessing the quality of insulating materials used in cables, terminations, and joints. Initial DF values are crucial in determining moisture content and deterioration.
The standard tests to calculate the dissipation factor for plastics include ASTM D2520, ASTM D150, and IEC 60250. During testing, the sample must be flat and larger than the 50mm circular electrodes used for measurement. The test can be conducted at different frequencies, typically between 10Hz and 2MHz, depending on the specific application requirements.
Factors such as frequency, temperature, voltage, humidity, and weathering can significantly influence the dissipation factor of plastics. Therefore, when selecting polymers for electrical applications, it is essential to consider the desired dissipation factor range to ensure optimal performance and efficiency.
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Signal integrity
The dissipation factor of plastics is defined as the reciprocal of the ratio between the insulating material's capacitive reactance and its resistance (Equivalent Series Resistance or ESR) at a specified frequency. In simpler terms, it represents the ratio between the permittivity and the conductivity of an electrical insulating material. This property is measured in dimensionless units, indicating the amount of electrical energy absorbed and lost as heat when an electrical current passes through an insulating material.
For signal integrity, a low dissipation factor is desirable. This indicates that the insulating material is efficient at minimising energy loss. In electronic systems, this translates to better signal integrity, as the signal's energy is preserved rather than dissipated as heat. Most plastics exhibit lower dissipation factors at room temperature, making them suitable for use as insulators in high-frequency applications.
The dielectric loss factor, a related concept, is the product of the dielectric constant and the dissipation factor. It describes the total power loss in the insulating material and indicates how readily the material heats up in a high-frequency field. This is important for signal integrity because excessive heating can degrade signal quality and affect the reliability of electronic components.
Factors such as frequency, temperature, humidity, and weathering can influence the dissipation factor of plastics. For instance, an increase in temperature or humidity typically leads to a higher dissipation factor, which can be detrimental to signal integrity if left unchecked. Therefore, understanding and controlling these factors are crucial for maintaining signal integrity in electronic systems that utilise plastic insulating materials.
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Heat generation
The dissipation factor (DF or tan δ) is an electrical property of plastics and other insulating materials. It is defined as the reciprocal of the ratio between the insulating material's capacitive reactance and its resistance at a specified frequency. In other words, it is the ratio between the permittivity and the conductivity of the material. A low dissipation factor indicates high-quality, high-performance electrical or electronic systems.
The dissipation factor is crucial for electrical and electronic applications as it directly impacts signal integrity, energy efficiency, and heat generation in components operating at high frequencies or voltages. The lower the dissipation factor, the more efficient the insulator system. Most plastics have a relatively lower dissipation factor at room temperature.
The dissipation factor measures the electrical energy absorbed and lost when an electrical current is applied to an insulating material. This energy loss is primarily in the form of heat generation. The dielectric loss factor or loss factor of a material is another frequently used term for this phenomenon. It is the product of the dielectric constant and the dissipation factor, indicating the total power loss in the material.
The dissipation factor varies with frequency, temperature, and humidity, and it is important to carefully consider these operating conditions when selecting materials. For example, in applications such as 5G telecommunications, high-speed computing, and power electronics, where signal integrity and thermal management are critical, low dissipation values are desired to minimize energy loss and heat generation.
Additionally, the finite element method (FEM) and theoretical models can be used to predict and analyze heat generation during plastic deformation due to impact or deformation in other materials. These methods help understand the temperature profiles and heat dissipation in various scenarios, contributing to the overall understanding of heat generation associated with plastics and other materials.
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Frequently asked questions
The dissipation factor (DF) is a measure of the loss rate of energy of a mode of oscillation in a dissipative system. It indicates the inefficiency of a material to hold energy or behave as an insulating material.
Plastics are generally considered insulators, but they can transmit some electrical energy at higher frequencies. Most plastics have a relatively lower dissipation factor at room temperature, which indicates high-quality, high-performance electrical or electronic systems.
The dissipation factor is defined as the ratio of the power dissipated in a test material to the power applied to the sample. It is also defined as the reciprocal of the ratio between the insulating material's capacitive reactance to its resistance at a specified frequency.
