What is a Scroll Chuck?

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A self-centering chuck, also known as a scroll chuck, uses dogs (usually called jaws), interconnected via a scroll gear (scroll plate), to hold onto a tool or workpiece. Because they most often have three jaws, the term three-jaw chuck without other qualification is understood by machinists to mean a self-centering three-jaw chuck. The term universal chuck also refers to this type. These chucks are best suited to grip circular or hexagonal cross-sections when very fast, reasonably accurate (±0.005 inch [0.125 mm] TIR) centering is desired.

 

Sometimes this type of scroll chuck has 4 or 6 jaws instead of 3. More jaws grip the workpiece more securely if it is truly cylindrical, and thin-walled work will deform less. Four jaws are also useful for square bar work.

 

There are also independent-jaw (non-self-centering) chucks with three jaws.

 

There are hybrid self-centering chucks that have adjustment screws that can be used to further improve the concentricity after the workpiece has been gripped by the scroll jaws. This feature is meant to combine the speed and ease of the scroll plate’s self-centering with the run-out eliminating controllability of an independent-jaw chuck. The most commonly used name for this type is a brand name, Set-Tru. To avoid undue genericization of that brand name, suggestions for a generic name have included “exact-adjust”.

 

Three-jaw chucks are often used on lathes and indexing heads.

 

Di Chun Iron Work Co., Ltd. is the professional manufacturer of producing scroll chuck and kinds of power chucks. If you are interested in learning further specification and what do them look like, welcome to browse our website and feel free to contact with Di Chun.

 

 

Article Source: https://en.wikipedia.org/wiki/Chuck_(engineering)

What are Metal Bond Grinding Wheels and What Benefits Do They Offer?

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Extensively used in manufacturing diamond grinding wheels, metal bonds are manufactured utilizing three different processes: cold press, semi hot press and hot press modes.

Metal Bond Grinding Wheel
Cold press mode involves pressing the transition layer (no diamonds) and the working layer (with diamonds) of selected diamond portions to forms that on the body of the grinding wheel. These segments are then allowed to interconnect with the grinding wheel’s body via slots or teeth. Finally, cold press grinding wheels are placed into sintering furnaces where they are sintered without press.

 

Semi hot press mode improves on the cold press mode by complementing the sintering process. While grinding wheels are sintering in a furnace, applicable molds are applied and minimal to moderate pressure is added. However, any pressure applied is significantly lower than the amount of pressure applied in hot press mode.

 

Hot press mode directly sinters diamond particles in molds under preset pressure levels in sintering press machines. Diamond segments are then affixed on the grinding wheel using high frequency laser welding, high frequency welding or mosaic methods of mechanical welding.

 

Metal bond grinding wheels are produced when powdered metals or compounds containing cubic boron nitride or diamond are sintered on the wheel, resulting in exceptionally strong tools that maintain shape during rigorous use. In addition, metal bonding extends the life of grinding wheels by reducing the need for repeated dressings and continues being productive longer than market-brand super abrasives.

 

Benefits of Using Metal Bond Grinding Wheels

  • Because metal bond grinding wheels are sintered with cobalt, copper, mill, silver or stanum power, they work exceptionally well on a variety of surfaces (glass, refractories, ceramics, silicon, semi-conductors and quartz).
  • Whether used for tool cutting, glass grinding, ceramic grinding or form cutting, metal bond grinding wheels provide the longest, most superior quality of service before any type of maintenance is needed.
  • Metal bond offers the ability to perform outstanding interrupted cuts while retaining the tool’s original dimensions even during the most energetic grinding actions, including centerless, cylindrical, creep feed, deburring and cutoff applications.
  • Although resin bonds are more commonly used than vitrified or electroplated bonds, these bonds do not offer the hardness or wheel retention properties exhibited by metal bond grinding wheel.

 

As one of the most frequently seen machines in manufacturing plants requiring grinding applications, centerless grinders especially benefit from metal bond grinding wheels because of the slow, precise pace of material removal method demanded of these machines. Additionally, super abrasive centerless grinders necessitate powerful wheels such as metal bond grinding wheels that can effectively make predetermined alterations to products while reducing quality control issues that may arise if lesser quality wheels are used.

 

Best Diamond Industrial Co., Ltd. is the professional manufacturer of metal bond grinding wheel & CBN wheels. If you are interested in learning more information about grinding wheels or related products, welcome to contact with Besdia directly!

 

 

Article Source: http://blog.cdtusa.net/what-are-metal-bond-grinding-wheels-and-what-benefits-do-they-offer

Something You Need to Know about Height of Volleyball Nets

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The height of volleyball nets varies depending on the age group that is playing Volleyball. Logically, the net height is considerably lower for the younger players and it gets taller as the age group grows. Also, the net height for women is slightly lower than that for men’s volleyball, because females are typically smaller in height. The net is positioned at a height regardless of your age that requires a reasonable jump to get above it (unless you are unusually tall). For a tall Volleyball player, usually they can just reach the top of the net without jumping, but you wouldn’t be able to block or hit the ball over straight down without jumping.

 

What this means is that you need to learn to jump as high as possible. In fact, the taller that you can reach the more chance you have of getting the ball down on the opponent court. Some of the tall players in volleyball are able to jump up a meter in the air, meaning that their total reach is often near 3 and a half meters! The full net height for males is 2.43 meters, and for females it is 2.24 meters. The net height is adjusted by loosening the net with the winch, undoing the pin that goes through the net pole, sliding the net up and then fitting the pin in again. From there, you simply wind the net back up so it is taught.

 

You might think that just because you aren’t tall that you have no chance of being a good spiker. In experience, those that are smaller have bigger jumping abilities, meaning that they have about the same height jump as someone who is tall. Of course, being tall has its advantages for blocking and spiking. You can always increase your vertical jump, but you aren’t always able to grow more!

 

Check out Holyhoe’s volleyball nets for selection. Holyhoe provides the complete solutions for the sports’ nets and accessories and we have been supplying high quality products to the international customers around the globe. Welcome to contact us to learn further details about volleyball nets!

 

 

Article Source: http://EzineArticles.com/5670379

Employing Lifting Magnets for Material Handling Operations

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Magnetic lifters are a lightweight and cost-effective way of transporting heavy materials in situations where another method of material handling would be difficult, dangerous, or expensive.

 

These lifters use magnets to hold heavy materials securely without requiring clamps, slings and other holding equipment. They are most beneficial in situations in which another method of material handling would be difficult, dangerous, or expensive.

 

Lifting magnets vary widely in size. Usually, the larger ones are hung from a chain on a crane that is able to move the lifting magnet into the location necessary to retrieve the material. This type of lifter can be used for a wide variety of purposes, including automobile junking, construction, and demolition and cleanup.

 

How Lifting Magnets Work

 

There are two types of lifting magnets: permanent magnets and electromagnets. Permanent magnets use permanently magnetized material to create a magnetic field. They can be used to lift loads up to 2,200 pounds. These lifters can be moved easily to various work locations. However, one disadvantage of permanent magnets is that they have a restricted lifting capacity. If a variable lifting capacity is required, the optimum choice is the electromagnetic lifter.

 

Electromagnetic lifters use an energized electrical coil wound around a steel core to orient magnetic domains within ferrous materials in a common direction, thus, creating a magnetic field. Unlike permanent magnets, electromagnets require a constant DC power source. Hence, a power failure can be a safety issue with electromagnets unless an emergency power or backup supply is integrated with this type of lifting system.

 

Permanent magnets are favored (1) when electricity is not available, (2) when power failures are a common occurrence, or (3) when adjustable magnetic force is not necessary. Electromagnets are the choice for applications where varying strength or remote magnet control is required.

 

Suitable Applications for Lifting Magnets

 

Smooth, Flat Surfaces: Permanent lifting magnets are manually operated. They create a very strong but low magnetic field so they are sensitive to air gaps between the magnet and the load. When an air gap increases, the magnetic force will be significantly reduced. They work best on smooth, flat surfaces rather than rough and irregular ones.

 

Type of Material: While ferromagnetic materials are inherently magnetize-able, paramagnetic materials, such as aluminum and magnesium are not. (Diamagnetic materials, such as copper, lead, and silver, do not magnetize.) For materials other than iron-based materials, a reduction factor must be calculated to determine the effective holding force.

 

Thickness of Material: The thickness of the material to be lifted also plays a role factor in selecting a lifting magnet. Thick materials are the best candidates. Materials thinner than the specification for the lifting magnet will have a much lower level of holding force.

 

Benefits

 

Lifting magnets save time by reducing and sometimes eliminating blocking and slinging. They can also eliminate or decrease waste. They reduce product damage commonly caused by chains, hooks, and other mechanical grabs. But the significant advantages of lifting magnets are ease of operation and cost-effectiveness.

 

Earth-Chain Enterprise Co., Ltd. is a professional manufacturer of specializing in lifting magnet, magnetic precision tools, magnetic clamping block, and etc. magnetic tools. If you are interested in learning further details about our lifting magnet series, welcome to browse Earth-Chain’s website or contact with us directly!

 

 

Article Source: http://EzineArticles.com/6074964

What are CNC Tool and Cutter Grinder and Its Applications?

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Today’s tool and cutter grinder is typically a CNC machine tool, usually 5 axes, which produces endmills, drills, step tools, etc. which are widely used in the metal cutting and woodworking industries.

 

Modern CNC tool and cutter grinders enhance productivity by typically offering features such as automatic tool loading as well as the ability to support multiple grinding wheels. High levels of automation, as well as automatic in-machine tool measurement and compensation, allow extended periods of unmanned production. With careful process configuration and appropriate tool support, tolerances less than 5 micrometers (0.0002″) can be consistently achieved even on the most complex parts.

 

Apart from manufacturing, in-machine tool measurement using touch-probe or laser technology allows cutting tools to be reconditioned. During normal use, cutting edges either wear and/or chip. The geometric features of cutting tools can be automatically measured within the CNC tool grinder and the tool ground to return cutting surfaces to optimal condition.

 

Significant software advancements have allowed CNC tool and cutter grinders to be utilized in a wide range of industries. Advanced CNC grinders feature sophisticated software that allows geometrically complex parts to be designed either parametrically or by using third party CAD/CAM software. 3D simulation of the entire grinding process and the finished part is possible as well as detection of any potential mechanical collisions and calculation of production time. Such features allow parts to be designed and verified, as well as the production process optimized, entirely within the software environment.

 

Tool and cutter grinders can be adapted to manufacturing precision machine components. The machine, when used for these purposes more likely would be called a CNC Grinding System.

 

CNC Grinding Systems are widely used to produce parts for aerospace, medical, automotive, and other industries. Extremely hard and exotic materials are generally no problem for today’s grinding systems and the multi-axis machines are capable of generating quite complex geometries.

 

Top Work is the expert of manufacturing tool and cutter grinders. We specialize in the grinder development to diversify our products and elevate the quality. If you are interested in learning further details about tool grinders, welcome to browse Top Work’s website and feel free to contact with us via Email or phone.

 

 

Article Source: https://en.wikipedia.org/wiki/Tool_and_cutter_grinder

Overview and Basic Design of Valve Stem Oil Seals

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Valve stem oil seals are small relative to other gaskets and seals in an engine, but play an important role in lubrication. What makes valve stem seals different than almost every other type of seal? The answer is simple – they are designed to leak. Seals designed to leak may sound counter-intuitive, but the amount and way in which they leak is precisely controlled to achieve a specific goal.

 

Valve stem seals provide a controlled leak of oil to allow the valve stem to be lubricated as it slides in the valve guide. The amount of oil that passes by the valve stem seal must be precisely controlled, as too little oil causes stem and guide wears. Too much oil causes carbon buildup leading to valve seat damage, decrease in volumetric efficiency, increased emissions and excessive oil consumption.

 

There are two basic valve stem oil seal designs:

 

  1. Deflector seals – also called umbrella seals, deflect oil away from the valve stem. They are secured to the valve stem and move with the valve to shield the valve guide from excess oil. Umbrella type seals were commonly used prior to the development of positive type seals.

 

  1. Positive seals – attach to the valve guide boss and function as squeegees, wiping and metering oil on the stem as they pass through the seals.

 

AOK supplies high quality Valve Seals for cars such as Alfa Romeo valve seals, BMW vehicle valve seal and motorcycle’s, etc… In order to maintain high quality, the valve stem oil seals from AOK are all inspected thoroughly, therefore, AOK has won worldwide recognition.

 

If you are looking for various rubber parts, oil seal, or others, please don’t hesitate to contact with AOK via phone call or email. Let us know your requirements to find what you need.

 

 

Article Source: http://www.felpro-only.com/blog/valve-stem-seals_/

Fishing Waders Help Keep You Dry

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Getting a good start in fly fishing as a new hobby can be as easy as making a list of all the equipment you will need. Keeping dry while wading is very important so a good place to start would be with fly fishing waders.

 

This all important piece of equipment is a pair of overalls with straps that go over your shoulders and cover your chest with a pair of rubber boots that fit over your feet keeping them dry. Hip waders are also available with rubber boots.

 

When looking at hip waders keeps in mind they look like two large rubber boots that fit up to the hip. These waders will help keep the fisherman dry while offering support from the padded reinforced knees. This feature comes in handy if the fisherman takes a fall or needs to kneel down. Discount fishing waders can be found in both chest and hip fishing waders.

 

Hodgman pants are one of the popular brands chosen by fly fishermen. When shopping for waders, hip or chest online it is important to have measurements for chest, outseam, inseam and shoe size. If shopping at the local sporting goods store the salesman will be able to help with measurements or the waders can be tried on before buying.

 

When shopping for waders check out simms fishing boots. The simms fishing waders are made with five layers of material that prevents tears around the chest area, is waterproof, and comes with hand warmers and a zippered chest pocket.

 

PACIFIC EAGLE Enterprise Co., Ltd. is a specialized OEM company. We have engaged in manufacturing of neoprene, hunting and fishing field products for over 25 years. If you are interested in learning more information about simms fishing waders or other waders, welcome to visit our website or fill out the form at Pacific Eagle for any technical support or requests for quotations.

 

 

Article Source: http://EzineArticles.com/3591673

The Importance of Having a Reach Truck or Forklift

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A lifting truck is very much like a forklift, but there is a small difference. This kind of vehicle is like a small forklift, designed for small aisles. They are usually electric powered and are named reach trucks because the forks extend to reach a load. Having a lifting truck in your warehouse or facility can increase your work efficiency and overall warehouse performance. Apart from this, there are many more other benefits you should consider when purchasing a lifting machine. I recommend you speak to a dealer or manufacturer about the benefits a reach truck can add to your business. One of the many benefits of owning an electric powered lift vehicle is that it costs way less to maintain than other types of forklifts. This is because they do not contain as many moving parts and do not need any type of fuel. They cost less to operate on per hour compared to a diesel or petrol powered forklift.

 

However, not everyone can afford to buy all the machinery and equipment they would need to run business. Not every business is as successful. Luckily, there are things like truck hiring companies. Truck hiring companies enable smaller businesses that use heavy machinery and equipment like reach trucks. Reach truck hire have become extremely popular and small businesses find this type of service very helpful. Companies that might only use reach trucks every now and then for small, irregular projects also find reach truck hire companies useful.

 

One distinctive difference between regular forklifts and reach trucks is that reach truck has the ability to lift pallets in a vertical fashion. This is especially helpful if you have a warehouse that utilizes high storage racks that might be difficult to reach.

 

Forklifts and lifting trucks are used for a number of different reasons, as we know. They are a critical element to warehouses and distribution centers, so much so that the warehouse efficiency and overall performance of the business would be noticeably decreased if without one. Obviously, like with most vehicles and heavy machinery, a forklift or lift truck driver would need to have a license to be able to operate these machines. Often times, drivers of these machines will have to be guided into the warehouse or factory through guide rails laid out on the floor.

 

Forklifts, lifting trucks and any other type heavy machinery often come with a nameplate that indicates, amongst others, the weight the machines are able to handle: normally between one and five tons. Larger machines that have up to fifty ton loading capacity are used to load larger objects, like shipping containers. The information located on the nameplate is extremely important and should never be ignored or removed: loads must not exceed these limits, as it can be extremely dangerous. In many jurisdictions, it is illegal to remove or tamper with the nameplate without permission from the machine’s manufacturer.

 

Forklifts and lift trucks are essential equipment in some industries. If you are interested in learning more information about reach truck, welcome to browse the website of Global Power Co., Ltd. The company has been a specialist for the world’s brand of lift trucks from China. The models of CT POWER forklift truck are compact and have obtained the certification of CE and ISO 9000, which have so far won good reputation among customers from Europe, Middle East, U.S A., Canada, Southeast Asia, etc.

 

 

Article Source: http://EzineArticles.com/5942500

SMPS: Basics & Working of Switched Mode Power Supply

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Switching mode power supply (SMPS) is used in a range of applications as an efficient and effective source of power. This is in major part to their efficiency. For anybody still working on a desktop, look for the fan output in the central processing units (CPU). That’s where the SMPS is. SMPS offers advantages in terms of size, weight, cost, efficiency and overall performance. These have become an accepted part of electronic gadgets. Basically it is a device in which energy conversion and regulation is provided by power semiconductors that are continuously switching “on” and “off” with high frequency.

 

The different kinds

  • C. to D.C. Converter
  • Forward Converter:
  • Flyback Converter:
  • Self-Oscillating Flyback Converter
  • DC-DC converter

 

The primary power received from AC main is rectified and filtered as high voltage DC. It is then switched at a huge rate of speed and fed to the primary side of the step-down transformer. The step-down transformer is only a fraction of the size of a comparable 50 Hz unit thus relieving the size and weight problems. We have the filtered and rectified output at the secondary side of the transformer. It is now sent to the output of the power supply. A sample of this output is sent back to the switch to control the output voltage.

 

Forward converter

 

In a forward converter the choke carries the current when the transistor is conducting as well as when it’s not. The diode carries the current during the OFF period of the transistor. Therefore, energy flows into the load during both the periods. The choke stores energy during the ON period and also passes some energy into the output load.

 

Flyback converter

 

In a flyback converter, the magnetic field of the inductor stores energy during the ON period of the switch. The energy is emptied into the output voltage circuit when the switch is in the open state. The duty cycle determines the output voltage.

 

Self-Oscillating Flyback Converter

 

This is the most simple and basic converter based on the flyback principle. During the conduction time of the switching transistor, the current through the transformer primary starts ramping up linearly with the slope equal to Vin/Lp. The voltage induced in the secondary winding and the feedback winding make the fast recovery rectifier reverse biased and hold the conducting transistor ON. When the primary current reaches a peak value Ip, where the core begins to saturate, the current tends to rise very sharply. This sharp rise in current cannot be supported by the fixed base drive provided by the feedback winding. As a result, the switching begins to come out of saturation.

 

Basic working concept of a SMPS

 

A switching regulator does the regulation in the SMPS. A series switching element turns the current supply to a smoothing capacitor on and off. The voltage on the capacitor controls the time the series element is turned. The continuous switching of the capacitor maintains the voltage at the required level.

 

Design basics

 

AC power first passes through fuses and a line filter. Then it is rectified by a full-wave bridge rectifier. The rectified voltage is next applied to the power factor correction (PFC) pre-regulator followed by the downstream DC-DC converter(s). Most computers and small appliances use International Electrotechnical Commission (IEC) style input connector. As for output connectors and pinouts, except for some industries, such as PC and compact PCI, in general they are not standardized and are left up to the manufacturer.

 

Why SMPS

 

Like every electronic gadget, switching mode power supplies also involve some active and some passive components. And like every of those gadgets, it has its own advantages and disadvantages.

 

Let’s start with why you should go for a SMPS

 

  • The switching action means the series regulator element is either on or off. Very high efficiency levels are achieved as very little energy us dissipated as heat.
  • As a result of the high efficiency and low levels of heat dissipation, the switch mode power supplies can be compact.
  • Switch mode power supply technology also provide high efficiency voltage conversions in voltage step up or “Boost” applications and step down or “Buck” applications.

 

Then there’s the bad set

 

  • The transient spikes due to the switching action can migrate into other areas of the circuits if not properly filtered. These can cause electromagnetic or RF interference affecting other nearby items of electronic equipment, particularly if they receive radio signals.
  • To ensure that a SMPS performs as per the required specification can be a bit difficult. The ripple and interference levels are particularly tricky.
  • The costs of a switch mode power supply is calculates before designing or using one. Additional filtering further adds to the cost.

 

What would the future hold?

 

In the future, we could have more efficient SMPS aimed at a better converter doing the most effective conversion process. The focus areas for designers in making SMPS efficient would be:

 

  • Higher output power
  • Achieving higher current output and low voltage
  • Increasing power density
  • Using switching device like Schottky diode

 

Hon-Kwang Electric specialized in manufacturing switch mode power supply and related products. We provide series of switching power supplies to meet different demands of you. If you are interested in learning more details about switching mode power supply, please feel free to contact with Hon-Kwang.

 

Article Source: http://electronicsforu.com/resources/learn-electronics/smps-basics-switched-mode-power-supply

Choosing the Best Option for Overcurrent Circuit Protection

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When it comes to overcurrent protection of electronic equipment, fuses have long been the standard solution. They come in a wide variety of ratings and mounting styles to fit virtually any application. When they open, they completely stop the flow of electricity, which may be the desired reaction; the equipment or circuit is rendered inoperable, which draws the user’s attention to what may have caused the overload condition so that corrective action can be taken.

 

Nevertheless, there are circumstances and circuits where auto-recovery from a temporary overload without user intervention is desirable. Positive temperature coefficient (PTC) thermistors – also called polymeric positive temperature coefficient devices (PPTCs) or resettable fuses – are an excellent way of achieving this type of protection.

 

Ceramic PTCs are also widely available through possess different operating characteristics including greater internal resistance, higher ambient heat tolerance, and higher voltage ratings. As they are typically used within high ambient heat areas including heating equipment applications not common to many electronics requirements, they were not factored within the scope of this article.

 

How a PTC works

 

A PTC resettable fuse consists of a piece of polymer material loaded with conductive particles (usually carbon black). At room temperature the polymer is in a semi-crystalline state and the conductive particles touch each other, forming multiple conductive paths and providing low resistance (generally about twice that of a fuse of the same rating).

 

When current passes through the PTC it dissipates power (P = I2R) and its temperature increases. As long as the current is less than its rated Hold Current, IHOLD, the PTC resettable fuse will remain in a low-resistance state and the circuit will operate normally. When the current exceeds the rated Trip Current, ITRIP, the PTC heats up suddenly. The polymer changes to an amorphous state and expands, breaking the connections between the conductive particles. This causes the resistance to increase rapidly by several orders of magnitude and reduces the current to a low (leakage) value just sufficient to keep the PTC in the high-resistance state – generally from around tens of milliamps to several hundred milliamps at rated voltage (Vmax). When the power is shut off the device cools down and returns to its low-resistance state.

 

Like a fuse, a PTC is rated for the maximum short circuit current (IMAX) it can interrupt at rated voltage. IMAX for a typical PTC is 40A, and may reach 100A. Interrupting ratings for fuses of the sizes that may be used in the sorts of applications we are considering here can range from 35 to 10000 amperes at rated voltage.

 

The voltage rating for a PTC is limited. PTC resettable fuses for general use are not rated above 60V operating voltage (there are PTCs for telecom application with 250V and 600V interrupting voltage, but their operating voltage is still 60V); surface-mount and small cartridge fuses are available with ratings from 32V to 250V or more.

 

The operating current rating for PTCs ranges up to about 9A, while the maximum level for fuses of the types considered here can exceed 20A, with some available to 60A.

 

The useful upper temperature limit for a PTC is generally 85°C, while the maximum operating temperature for thin-film surface mount fuses is 90°C, and for small cartridge fuses is 125°C. Both PTCs and fuses require derating for temperatures above 20°C, although PTCs are more sensitive to temperature (Fig.2). When designing in any overcurrent protective device, be sure to consider factors that may affect its operating temperature, including the effect on heat removal of leads/traces, any air flow, and proximity to heat sources. The speed of response for a PTC is similar to that of a time delay fuse.

 

Common PTC applications

 

Much of the design work for personal computers and peripheral devices is strongly influenced by the Microsoft and Intel System Design Guide which states that “Using a fuse that must be replaced each time an overcurrent condition occurs is unacceptable.” And the SCSI (Small Computer Systems Interface) Standard for this large market includes a statement that “… a positive temperature coefficient device must be used instead of a fuse, to limit the maximum amount of current sourced.”

 

PTC resettable fuses are used to provide secondary overcurrent protection for telephone central office equipment and customer premises equipment, alarm systems, set top boxes, voice over IP (VOIP) equipment and subscriber line interface circuits (SLICs). They provide primary protection for battery packs, battery chargers, automotive door locks, USB ports, loudspeakers and power over Ethernet.

 

SCSI Plug and Play applications that benefit from PTCs include both the mother-board and the many peripherals that can be frequently connected to and disconnected from the computer ports. The mouse, keyboard, printer, modem and monitor ports represent opportunities for misconnections and connections of faulty units or damaged cable. The ability to reset after correction of the fault is particularly attractive.

 

A PTC resettable fuse can protect disk drives from the potentially damaging overcurrent resulting from excessive current from a power supply malfunction.

 

PTC resettable fuses can protect power supplies against overloading; individual PTCs can be placed in the output circuits to protect each load where there are multiple loads or circuits.

 

Motor overcurrent can produce excessive heat that may damage the winding insulation and for small motors may even cause a failure of the very small diameter wire windings. The PTC will generally not trip under normal motor start up currents, but will act to prevent a sustained overload from causing damage.

 

Transformers can be damaged by overcurrent caused by circuit faults, and the current limiting function of a PTC can provide protection. The PTC is located on the load side of the transformer.

 

Fuse or PTC?

 

The following procedure will help in selecting and applying the correct component. Help is also available from device suppliers. For unbiased advice it is wise to look for a company that offers both fuse and PTC technology.

 

  1. Define the circuit operating parameters. Consider the following: normal operating; current in ampere; normal operating voltage in volts; maximum interrupt current; ambient temperature/rerating; typical overload current; required opening time at specific overload; transient pulses expected; resettable or one-time; agency approvals; mounting type/form factor; typical resistance (in circuit).

 

  1. Select a prospective circuit protection component.

 

  1. Determine the opening time at fault. Consult the Time-Current (T-C) Curve to determine if the selected part will operate within the constraints of the application.

 

  1. Verify ambient operating parameters. Ensure that the application voltage is less than or equal to the device’s rated voltage and that the operating temperature limits are within those specified by the device

 

  1. Verify the device’s dimensions. Compare the maximum dimensions of the device to the space available in the application.

 

  1. Test the selected product. Independently test and evaluate suitability and performance in the actual application.

 

Zonkas is the professional manufacturer of capacitor, inductor and transformer. Our main products including: various inductors, transformers, Safety Capacitor (Y1, Y2, X1, X2), Ceramic Capacitor, Film Capacitor and Electrolytic Capacitor. If you need more information about PTC resettable fuses or other capacitors, welcome to visit our website or contact with Zonkas directly!

 

 

Article Source: http://www.engineerlive.com/content/21341