Powerderatingdesign电源降额设计

Powerderatingdesign电源降额 设计 领导形象设计圆作业设计ao工艺污水处理厂设计附属工程施工组织设计清扫机器人结构设计 Reference & Information Guideline for Derating Electronic Components This page provides a number of guide-lines for Voltage and Temperature derating [Thermal Derating]. Derating guidelines are provided in tables for each component type, and should be regarded as design recommendations. A good design always uses components that operate within their Safe Operating Region. However there are absolute rules of design that should be followed when designing circuits. The derating curves provided for Transistors, FETs, and Diodes should be considered rules to hold the junction temperature of these devices within specified limits. These component derating recommendations do not account for mounting issues required by high vibration environments. A short description is provided as required to understand How-to derate components; Connector Voltage Derating: Derate connector voltage to 25% of rated operating voltage .... Operating voltage = Connector rating / 0.25 oDerate connector operational temperature by 50C o.... Connector rating = operating temperature + 50C Current is normally specified as some number of pins carrying some specific amount of current, at some defined temperature. Increase the current carried over any particular pin and the number of pins carrying current most decrease. Decreasing the amount of current over the defined pins may allow more pins to carry current. Main section on Connector Derating. Refer to this page for a manufacturers listing for Connectors Cable/Wire Derating: Refer to this page for a manufacturers listing of Wire and Cable. Cable manufacturers will provide different numbers based on the insulation used for the wire. The table below lists copper wire with a Teflon [TFE] insulation. Teflon insulation has a higher operation temperature range then other insulators, for example PVC. The table below is based on data oderived from MIL-STD-975, using 70C as the operating temperature. To derate based on number of wires in a bundle: I = I x (29 - #) / 28 @ [1 to 15 Bundled wires] BWSWwire I = I x (0.5) @ [more then 15 Bundled wires] BWSW I = Single wire SW I = Bundled wires BW000To derate by temperature use; derate by 80% at 150C, 70% at 135C, or 50% at 105C {Per MIL-STD-975} To derate for Commercial wire use the table below; Copper Wire Correction Temperature Derate Ampacity o40C 0.88 o45C 0.82 o50C 0.75 o55C 0.67 o60C 0.58 o70C 0.33 Ampacity Tables for many conditions (Commercial Wiring): IEEE Standard 835, IEEE Standard Power Cable Ampacity Tables IEEE Standard 848, Procedure for the Determination of the Ampacity De-rating of Fire Protected Cables ICEA P-54-440, NEMA Pub. No. WC 51 - Ampacities of Cables in Open-Top Trays Use the National Electrical Code [NEC] system for premises wiring, and not the Military data on this page. Voltage Drop per Foot: V = I x L x (R/1000) x 1.004 x (T-20) V = Voltage Drop, I = Current, R = Resistance per 1000 foot oL = Length of wire in feet, T = Estimated wire Temperature under load C Refer to the AWG Table for Resistance per length Copper Wire TFE Insulated AWG Current Carrying AWG Current Carrying 169 147 00 0 108 81 2 4 60 44 6 8 33 4425 10 12 19 13 14 16 9.2 6.5 18 20 4.5 3.3 22 24 2.5 1.8 26 28 1.3 - 30 - {Component Derating Guidelines} Potentiometer Derating: Potentiometer Derating Curve A list of Potentiometer manufacturers This page shows the derating curve for an Adjustable WireWound resistor {Component Derating Guidelines} Resistor Derating Example: oPower ratings are normally specified at +25C and must be reduced as the resistors otemperature increases. A derating chart is often used, with derating starting at 70C. Since parameters are application dependent, charts should be considered general rather than absolute, and only used as a guideline. However power de-rating curves should be considered more of a recommendation than a guideline The safest designs use the largest physical size operating at conservative temperatures and power ratings. Combining the resistor application and a power de-rating curve should start to form a design rule, once the location of the resistor on the PWB is known and the components around the device. Resistor Derating Chart Wire Wound Metal Film % Rated load Temperature Temperature oo100% 70C 70C oo80% 110C 85C oo60% 150C 100C oo40% 190C 120C oo20% 240C 140C oo10% 260C 145C Military Resistor Derating Curves, Derating Resistor Networks, Derating Thermistors. A list of Resistor Manufacturers manufacturers Design guidelines; For resistors mounted in series, consider the heat being conducted through the leads to the next resistor. At the same time axial lead-mounted parts also act as a heat dissipator and allow heat to be conducted away from the device and into the printed circuit card, or pads on the PCB. Of course heat is also removed from the component via convection and radiation. Large power resistors should be mounted to the metal chassis for heat dissipation. Do not mount resistors with power dissipation 1 Watt directly on terminal or printed wiring boards without use of heat sinks. A resistor that dissipates over one watt can damage a terminal board. A damaged board will have a lower insulation resistance. For the most efficient operation and even heat distribution, power resistors should be mounted in a horizontal position. {Component Derate Guideline} Fuse Derating: Fuses are specified to interrupt within a maximum of 5 seconds when driven at 200% of their rated current for nominal ratings up to and including 10 amperes. A fuse with a nominal rating of 15 amperes is specified to interrupt within a maximum of 10 seconds when driven at 200% of its rated current. The power supply shall be capable of delivering appropriate levels of current to achieve short fusing times. There is an additional derating of 0.2%/?C for an Fuse Derating Guidelines page. AC or DC increase in the temperature of fuse body. Main Fuse operation. Fuse holders may also require derating. A manufacturers listing for Fuses {Component Derating Guidelines} Switch Derating: Switch Temperature Correction Current Derating Factor @ Application Ambient Temperature Military Commercial ooooooLoad Type 0C to 85C Above 85C 0C to 85C Above 85C 75% of rated 60% of rated 75% of rated 60% of rated Resistive Resistive load Resistive load Resistive load Resistive load Inductive / 75% of rated 60% of rated 40% of rated 30% of rated Motor Inductive load Inductive load Resistive load Resistive load Capacitive / 75% of rated 60% of rated 25% of rated 20% of rated Lamp Capacitive load Ca pacitive load Resistive load Resistive load Note the derating factor changes with the type of load. A manufacturers listing of Mechanical Switches {Component Derating Guidelines} Inductor Derating: Inductor Temperature Correction Current Derating Factor @ Application Ambient Temperature Military Commercial oooooo Load Type 0C to 85C Above 85C 0C to 85C Above 85C 75% of rated 60% of rated 75% of rated 60% of rated Resistive Resistive load Resistive load Resistive load Resistive load Inductive / 75% of rated 60% of rated 40% of rated 30% of rated Motor Inductive load Inductive load Resistive load Resistive load Capacitive / 75% of rated 60% of rated 25% of rated 20% of rated Lamp Capacitive load Capacitive load Resistive load Resistive load Inductors are also derated by reducing the maximum operating temperature based on the insulation class and reducing the operating voltage. Transformer Stress Ratio = Operating VA Load / Rated VA Load = 80% [Rule-of-Thumb Operating Recommendation] A manufacturers listing of Inductor Vendors, Transformer Vendors, Choke Vendors {Component Derating Guidelines}