Automated highvoltage creepage checks eliminate the tedious work associated with pcb validation and make it easy to find design errors. In the presence of contamination, the surface resistance is reduced more drastically. Clearance is the shortest distance between two conductive parts, or between a conductive part and ground, measured through air or other insulating medium. Clearance, creepage and other safety aspects in mysensors. May 18, 2017 creepage distance is the shortest path measured along the surface of the insulator. However, for products covered by legal safety standards, creepage and clearance. The rating of clearance and creepage distances depends on the expected electrical surge, the characteristic values of the electronic protection measures as well as the contamination at the place of installation. Saturn pcb toolkit saturn pcb design pcb design service. And for pd3 they suggest to follow distance for other. A detailed overview of the calculation of the clearance and creepage distance is available as a download. The clearances for air and creepage surface will usually be different. You can see that the carbon trace continues between the two adjacent pads on the left, but. The greater the creepage distance, the higher the external safety protection.
Not relevant to this project but im curious for the future. Clearance denotes the shortest distance between two conductive parts as measured through the air. I want to know track width, clearance and creepage distance that compatible with iec, ul standard. For a group greater than one millimeter wide, the depth requirement is that existing creepage distance plus the width of groove and twice the depth of the groove must equal or exceed the. Creepage distances the shortest distance along of the surface of an insulating material between two conductive parts, specified for normal usage and modified by environmental conditions such as the degree of environment. I am having an argument with another person here at work regarding creepage distances between the coil and armature of a.
The creepage distance is important when electric potential reaches high level. Jun 06, 2018 clearances the shortest distance between two conductive parts, specified for nominal voltage and overvoltage. If you are not yet familiar with the ipc2152 then please be aware that there are two separate charts for finding conductor current vs. Im designing a pcb which i want to connect to 230v ac. This rule tests the creepage distance between the targeted signals across the board surface through unplated holes, cutouts, and around the board edge. I have seen customers cut a slot in their circuit board to allow them to reduce the overall circuit board size. I am having an argument with another person here at work regarding creepage distances between the coil and armature of a js1 relay. The creepage distance is also a function of the power frequency voltage that may have small impact with altitude. However, when it comes to distances between the pc traces, in my view, the ipc2221 table 61 stepwise limits are mostly baseless. Using an ipc2221 calculator for high voltage design pcb. Of course, it is not the only standard that defines the electrical clearance. Primarytoprimary creepage distance acdc converters.
However, it is interesting to note that when it comes to functional insulation in secondary circuits, ul requirements are not necessarily more stringent than ipc. Creepage distance is the shortest path between two conducting parts of an electrical or electronic circuit measured along the surface of the insulator. Note that if you put a pcb inside a sealed component you get pollution level 1. In addition there exists an ammendmend a1 since 2012. Clearance, creepage and other safety aspects in mysensors pcbs. Note 1 this definition differs from that of specific creepage distance where the linetoline value of the highest voltage for the equipment is used for a. Understanding pcb creepage and clearance standards tempo. Since there are engineers from all over the world and from all different industries here, i thought it would be interesting to hear what you guys use as far as creepage and clearance rules in your pcb designs and why. The results of the creepage distance and clearance analysis is shown as a percentage of the specified distance parameters. Creepage distance is the shortest path measured along the surface of the insulator. Creepage distance for pcbs handling line voltage ac. Clearance is defined as a straight line distance in air between two points. An ipc2221 calculator helps ensure your next high voltage design. Isolation means that no direct electrical connection, or conductor, exists between two or more circuits or between circuits and.
The minimum clearance distance up to installation heights of 2000 m above sea level is determined from the rated surge voltage and the pollution severity. Creepage is the distance between the edges of the lead connections at the surface of the pcb. Creepage distance is also referred to as the leakage or creep distance. This seems to be true in stuff that ive disassembled, but i dont see why it has to be, as long as proper clearance creepage from the primary side is observed everywhere. White paper low voltage products in high altitudes 7 minimum creepage distances. Apr 01, 2016 when i first learned the terms of creepage and clearance, it was more in a legal setting. When dealing with ac, the general guideline is to multiply the rms voltage by three to determine the spacing. It could mean a sparkover the voltage is high for the creepage distance set. Creepage distance is the shortest distance separating two conductors as measured along the surface touching both. Basis of the creepage distance is the rated voltage derived from the operating and or system voltage. Also a single electric discharge could irreparably destroy or. Reflow, wave or hand soldering with high temperature requirements. What are pcb creepage and clearance, and how can you optimize your.
What is the creepage distance of current transformer. Pcb creepage and clearance requirements from around the. You can also use a high voltage clearance calculator based on the ipc. Creepage is the distance between two conductive points on the outside of a package.
This value depends on the specific application and contamination class, and is limited by the creepage distance of 76 mm 3. Also a single electric discharge could irreparably destroy or damage the linked components. All design rules are created and managed within the pcb rules and constraints editor dialog. When a medical device is developed, isolation between patient and mains voltage is a main concern. This seems to be true in stuff that ive disassembled, but i dont see why it has to be, as long as proper clearancecreepage from the primary side is observed everywhere. Id like to know the gap to leave between pcb tracks and in particular between adjacent pins on the transformer primary side. One would think that ul norms should be most stringent than ipc. When i first learned the terms of creepage and clearance, it was more in a legal setting. Protected creepage distance of an insulator means part of the creepage distance on the illuminated side of the insulator which would lie in shadow if light were projected on to the insulator at 90or 45in special cases to the longitudinal axis of the insulator. According to our arc gap calculator, this dimension could fail at around 1425 vdc. Figure 2 clearance and creepage external spacings are measured from inputstooutputs in clearance and creepage figure 2. May 01, 2018 this reduces the requirement on creepage and clearance by eliminating the influence of pollutants.
Safe distance includes electrical clearance space distance, creepage distance distance along the surface and insulation penetration distance. Adequate trace width is necessary to ensure the desired amount of current can be transported without overheating and damaging your board. For each calculated path segment between two points of contact, the software determines what proportion of the specification has been achieved. Clearances and creepage distances in lv electrical.
High voltage spacing evan mayerhoff high voltage connection, inc. Printed circuit board pcb base material fr4 type kf. The creepage distance, instead of simply straightline padtopad distance, is now measured between the corners of. Other techniques, such as groove cutting can be used to attain a lower pcb creepage distance. However, instead of measuring distance in air, it measures the shortest distance along the surface of the insulation material. Information and technical guidance for applications above. Specific insulator creepage distance is determined for the particular environment by experience from earlier installations. Download the latest in pcb design and eda software. Pcb creepage and clearance requirements from around the world. Conformal coatings can provide good protection and eliminate the path for breakdowns. What spacing should i use between the tracks to avoid arcing. Selection of ul standards for the coordination of insulation. Where shortage of space on a pcb is an issue, especially between primary and selv circuits, techniques such as slots or grooves can be used to attain desired creepage distance.
This program is based on table 2g and figure 2f of iec 60950. You will find limits on track spacing in relevant safety standards, such. Inform knowledge about pcb terminals and connectors. A proper and adequate creepage distanceprotects against tracking, a process that produces a partially conducting. Measurement of clearance and creepage distances according to ul w. In the second edition of the 606011, the necessary air clearances and creepage distances were defined in a.
Creepage is the shortest distance alone a material between two points. If no such information is available then for major projects the establishment of an energized test station or overhead line test section 1 or 2 years in advance of the insulator material procurement project programme should be established. Clearance requirements in ehv ais substation you must respect. Typical operating voltage potential between primary and secondary is 25kvrms. Groove cutting effectively extends the creepage distance. V mm 25 32 40 50 63 80 100 125 160 200 250 320 400 500 630 800 this voltage is for functional insulation, the working voltage, for basic and supplementary insulation of the circuit energized directly from the supply mains see 4. Moisture or particulate accumulation on the board can shorten creepage. Sep 07, 2016 the purpose of the insulator or insulation is to insulate the electrically charged part of any equipment or machine from another charged part or uncharged metal part creepage leakage distance is the shortest path between two conductive parts mea. Introduction how much spacing is needed in high voltage circuits and setups. You may use this online tool to calculate an estimate of the minimum trace width for a given current and copper weight. The following table gives for 888 v an interpolated creepage distance value of,32 mm. Dry arcing distance is the shortest distance outside the insulator along the air not along the insulator body and between those parts which normally have.
Seriously, though, creeping and clearance is no laughing matter. These tables specify socalled clearance and creepage distances for various. This is one of the most important parts by knowing your isolation grouptype you need to have for safety you enter this into the creepage calculator to get your creepage distance. This is troubling, as following these standards is a good way to ensure safety, even if you never intend to actually get your project ul or ce. Creepage is the separation between two pc board solder eyes as measured along the surface of the board. Some of the other connector creepage distances can be hidden. What is the creepage distance and protected creepage distance. The distance may mean the breakdown of an insulation specially in high voltage lines. The creepage distance between two points will increase if there is a slot in the pcb. What is the creepage distance and protected creepage. View blog entries view articles full member level 5 join date jun 2005 posts 240 helped 45 45 points 4,206. Ipc2221 is generally accepted in electronic industry as a generic pcb design standard. Creepage distance and protected creepage distance are main parameters for electrical insulator, especially creepage distance of insulator electrical insulator suspension type electrical insulator post type. The live parts of the machine must be isolated from the ground and operating person.
If it is less than 100%, the vulnerable path is highlighted in the analytics report. Pic ee creepage distances for pcb relay connections. Calculation of the clearance and creepage distance in accordance with vde iec and ul. Calculating creepage and clearance early avoids design problems later high. For safety reasons and for every certification iec, ul, csa it is essential that certain clearance and creepage distances are maintained. Jan 2007 location thailand posts 46 helped 3 3 points 1,437 level 8. Let it be current transformer or any other electrical device.
Clearances the shortest distance between two conductive parts, specified for nominal voltage and overvoltage. Similar to clearance, creepage measures distance between conductors on a pcb. Check for hidden creepage paths outside the connector. Safety, creepage, and clearance checks for pcb design. Board material and environment also affect creepage requirements. Understanding isolator standards and certification to meet.
Creepage distance an overview sciencedirect topics. Creepage is along the surface, as the ant walks, and clearance is shortest distance, as the bird flys. Dfm checks and enable you to easily view and download drc files. Unlike ipc requirements that deal with electrical clearance, iec and ul additionally specify socalled creepage. The clearance distance between the same two points will not increase. Clearance is the shortest distance between two circuits through air. Its quite common to see a routed slot in a pcb underneath things like optocouplers and transformers used for isolation.
The following is an excerpt from a publication from the university of quebec. Trace width is an important design parameter in pcb design. You can also use a high voltage clearance calculator based on the ipc2221 standards to determine the minimum spacing you should use for. The circuit designers guide and calculator of the spacing between pcb traces. Creepage distances are measured by the operating voltage, the characteristic of the insulants cti value, the expected contamination level as well as the preventive measures against contamination. Understanding isolator standards and certification to meet safety requirements. As always, the amount of it distances required for a given mode depends on the end system specification. Creepage leakage distance is the shortest path between two conductive parts or between a conductive part and the bounding surface of the equipment measured along the surface of the insulation. In practice, creepage and clearance on a pcb are the same initially. The creepage distance in air is much shorter than the creepage distance on a pcb surface. Pcb design toolkit a free download tool for calculating conductor spacing and.
In order to understand the pcb toolkit version differences, i have added this brief description of the version series. What creepage distances are required between nodes on the primary circuit side, to meet iec 60950 safety requirements. Determination of the rated surge voltage according to table 1 in the brochure below. Click the button below to download the latest altium designer. In the second edition of the 606011, the necessary air clearances and creepage distances were defined in a single table. Creepage distance for the avoidance of the failure by tracking download view. The minimum clearance creates a no mans land between the two sides of. I can use an insulator twice the strike distance, but 75% of the creepage distance of a comparable insulator, depending on the shed design and profile. If the connector solders to a pcb, inspect adjacent pcb pads for the connector contacts both on the top and bottom of the pcb. Now you can download a free trial of altium designer and learn more. The shortest distance between the high and low voltage points along the external insulating surface of an arresters weathersheds. For most types of apparatus, the creepage distance plays no part in the ability of the apparatus to withstand a bil or dry power frequency withstand test. Calculating creepage and clearance early avoids design.
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