月: 2023年1月

What Is a Closed-End Wire Connector?

A closed-end wire connector is a terminal component used to connect two or more electrical wires by crimping.

Electrical wiring uses copper as the core wire, which has extremely low resistance. Therefore, by bringing two or more core wires into contact with each other, electricity can be supplied to the end of the wiring. However, simply twisting the wires to make contact will generate contact resistance, which can cause sparking or ignition. To reduce contact resistance, when wiring is connected, the wires are stored in crimp terminals and held together with a crimping tool to make a strong connection.

A closed-end wire connector is a type of crimp terminal that is closed on one side.

Uses of Closed-End Wire Connectors

Closed-end wire connectors are used to connect new equipment as well as repair wiring in industrial equipment when the wiring has been pulled apart by a strong impact. Since it does not support wiring with a large cross-sectional area, it is used for connecting relatively thin wiring of 0.75 to 8 mm2.

For connection of new equipment, it is used to connect the lead wires of equipment to the power supply side. Electrical products with specific uses are delivered with the power wiring called lead wires exposed. Closed terminals are sometimes used when connecting these to a power supply device.

Principle of Closed-End Wire Connectors

Closed-end wire connectors are connection terminals and have a very simple structure. Specifically, it is divided into a conductor part and a sheathed part.

The conductor part is a metal cylinder, which is crushed to form a tight fit between the wires. It is only about 1mm or less in thickness. Therefore, it can be easily crushed by using a crimping tool. The feature is that the conductor entrance is slightly widened so that wires can be easily inserted. The material used is basically copper, the same material used for wiring.

The sheathed part covers the entire conductor except for the wiring entrance of the conductor section. Since it must be electrically insulated from its surroundings, an insulator is used. In most cases, inexpensive nylon is used. As the working voltage increases, simple insulation with nylon is dangerous, so the upper limit of the working voltage is about 200V.

When actually crimping, the wires are twisted, and inserted from the wiring entrance until they hit the sheathed part, and then connected. At this time, if the core wire of the wiring protrudes from the covered part, it will lead to an electric shock or ground fault. During installation, it is essential to confirm that the core wire is completely inside the sheath and that it cannot be easily removed by pulling by hand.

What Is a Transmission?

A transmission is a critical component in vehicles and machinery, facilitating the regulation of revolutions or torque. It enables speed ratio adjustments to suit various operating conditions, differing from reduction gears by offering variable rather than fixed ratios.

Uses of Transmissions

Transmissions are essential for the smooth operation of automobiles, motorcycles, trains, and machine tools, allowing for the efficient transfer of power from the engine to the drive mechanism. They adapt to different demands, such as providing more torque for uphill starts or higher speeds for cruising.

Principle of Transmissions

Using gears or pulleys, transmissions alter torque and speed between input and output shafts. Gear transmissions adjust these variables by changing gear sizes, while pulley systems use varying pulley diameters and a connecting belt to modify the output.

Types of Transmissions

There are mainly two categories: stepped and continuously variable transmissions. Stepped transmissions, including manual (MT) and automatic transmissions (AT), offer fixed speed changes, whereas continuously variable transmissions (CVT) allow for seamless ratio adjustments.

• Manual Transmission (MT): Requires the driver to manually shift gears, using a clutch to interrupt and resume power from the engine.
• Automatic Transmission (AT): Automates gear shifting based on the vehicle’s speed and load, using a torque converter for smooth transitions.
• Continuously Variable Transmission (CVT): Provides step-less ratio changes, available in belt and toroidal types, for smooth acceleration and enhanced fuel efficiency.

What Is a Protective Relay?

A protective relay is a device that instantly detects sudden changes in current and voltage occurring in power system equipment and sends a control signal to the circuit breaker to isolate the faulty point.

By quickly disconnecting the faulty part in the event of an accident in the power system, the protective relay not only prevents the spread of damage caused by overcurrents but also minimizes the duration of power outages and ensures a stable supply of electric power.

For this purpose, equipment fault elimination relays to isolate faulty equipment and accident spread prevention relays to prevent the spread of the effects of accidents are dispersed throughout the power system. A reclosing device for quick recovery from an accident is also treated as a type of protective relay.

Uses of Protective Relays

Protective relays are used to prevent the effects of accidents such as lightning strikes from spreading throughout the power system and to ensure a stable supply of electricity. Protective relays are installed in various places in facilities that make up power systems, such as power plants, substations, and power transmission and distribution lines managed by power companies.

Private power generation facilities that are connected to the power company’s power system are also required to install protective relays at the receiving points to protect the power system in the event of a failure of the private power generation facilities and to protect the private power generation facilities in the event of an accident on the power system.

In addition to power generation facilities, protective relays are also used to protect power receiving and transforming facilities in buildings, factories, hospitals, railroads, and other power-demand facilities.

Principle of Protective Relays

The operational principle of protective relays varies depending on the type of protective relays.

Over Current Relay (OCR): Operates when the current value at the location where the protective relays are installed exceeds the set value. There are two types of elements that trigger the overcurrent protective relays: dimensional elements and instantaneous elements. The dimensional element operates when it detects that an overcurrent has flowed for a long period of time due to an overload. The higher the current value, the sooner the normal system is protected. The instantaneous element detects the instantaneous flow of a large current far in excess of the rated current due to a short circuit and protects the normal system.

Over Voltage Relay (OVR): Operates when the voltage at the location where the protective relays are installed exceeds the set value. Detects overvoltage on the power system side due to a generator or other failure and protects the system and equipment on the load side.

Under Voltage Relay (UVR): Operates when the voltage at the location where the protective relays are installed drops below a set value. Detects a drop in power due to a power failure or short-circuit failure, and protects the load-side system and equipment.

Ground Fault Protective Relays (GR: Ground Relay): Operates by detecting ground faults caused by cables contacting the earth. Ground protective relays use a zero-phase alternator (ZCT) to detect unbalanced current due to an imbalance in the three-phase circuit in the event of a ground fault. At this time, since a ground fault is detected only by the magnitude of the current, it is not possible to distinguish between an accident current in the power system and an accident current on the self-circuit side, which may result in false detection.

Directional Ground Relay (DGR): Operates by detecting a ground fault using the zero-phase current and zero-phase voltage between the line and the ground. It can detect only the fault current of its own line in the direction of the phase difference between the current and voltage.

Differential protective relays (DFR: Differential Relay): Operates when the differential current, which is proportional to the vector (current value and phase) difference between the input and output currents in the protective section, exceeds a certain value. Only when a short circuit occurs in the protective section, a difference is generated in the secondary current of the alternator (CT), and a differential current flows to the operating coil. With this method, the differential current does not reach zero during normal operation due to the characteristic difference of the CT, etc., and may malfunction.

Ratio Differential Relay (RDFR): To prevent malfunction of the differential protective relays, differential protective relays have a structure with an additional suppression coil that generates a suppression force when a current passes through it. When a large current due to an external accident passes through the relay, a large suppression force is applied to prevent malfunction.

Other types of protective relay systems include power protective relays, over-frequency protective relays, under-frequency protective relays, short-circuit protective relays, and short-circuit direction protective relays.

What Is an Auxiliary Relay?

An auxiliary relay, or electromagnetic relay, controls the opening and closing of its contacts through an electromagnet. Functioning similarly to electromagnetic switches, auxiliary relays differ in contact configurations, facilitating precise control in protective and control relay circuits.

Uses of Auxiliary Relays

Employed primarily in control circuits, auxiliary relays enhance the reliability of contact connections, supporting applications requiring low energizing currents (under 10A). They’re pivotal in safety mechanisms like interlocks, ensuring operational control under specific conditions, and enhancing ground fault detection to prevent accidents.

Principle of Auxiliary Relays

Auxiliary relays incorporate make (a-contact), break (b-contact), and transfer (c-contact) contacts to manage circuit connections effectively. This versatility allows for adaptive use in various electrical configurations.

Structure of Auxiliary Relays

Comprising a coil wrapped around an iron core, an electromagnet, and contacts, auxiliary relays activate circuits by magnetically pulling together movable iron pieces, enabling contact closure. Their design often includes a twin-contact structure for improved reliability, especially for minute electrical loads.

Characteristics of Auxiliary Relays

Auxiliary relays are notable for their diverse contact configurations, accommodating from 2 to 16 contacts to meet specific circuit requirements. They are designed for a range of voltage specifications, ensuring compatibility with different electrical systems. The compact, lightweight design supports easy installation and high contact reliability, making these relays suitable for various applications, including space-constrained control panels.

What Is an Auxiliary Power Supply?

An auxiliary power supply is connected to the power supply unit of a main unit and is a power supply device that is used to supplement the power supply that tends to be in short supply, separately from the main power supply.

For example, if the main power supply of a railroad car is mainly used to drive the car, an auxiliary power supply is used to provide a stable power supply for the air conditioning and lighting in the car. Similarly, power supplies for graphic displays in personal computers are also typical auxiliary power supplies.

Note that an auxiliary power supply is also a power supply that receives power from the same power supply unit as the main unit.

Uses of Auxiliary Power Supplies

The main application of auxiliary power supplies is to provide a stable supply of power for air conditioning and lighting in railcars, as mentioned above.

High-voltage power (1500V to 2500V) supplied from overhead wires is converted to low-voltage power (440V to 100V) via an auxiliary power supplies unit. This is because most train cars are designed to use 100 VAC for various lighting and indicator lights, 3-phase 440V for air conditioning equipment, and 100 VDC for door opening/closing devices, etc.

Apart from this example, a storage battery-type power supply called a UPS is also an auxiliary power supply in the broad sense of the term, as it is used to protect personal computers and network computers from data loss due to instantaneous power failure in the event of a power company blackout.

Principle of Auxiliary Power Supplies

There are two main types of auxiliary power supplies for vehicles: MGs (Motor Generators) and SIVs (Stationary Inverters).

The MG, also called an electric generator, has long been used as an auxiliary power supply.

On the other hand, the SIV (Static Inverter) uses IGBTs, which are typical high-power semiconductor devices, in the inverter circuit. There are different types of SIVs, including 3-level, 2-level, and 2-level inverters, as withstand voltage improvements were made according to the IGBTs’ development period at the time. SIVs are also known as pulse-width modulation (PWM) control inverters, which can now be supported by small AC filters, contributing greatly to the miniaturization and high efficiency of auxiliary power supplies.

The low-voltage power supply generated by the SIV is an AC power supply. Therefore, the 100 VDC required for control equipment is converted by a rectifier.

What Is Packing Machinery?

Packaging machinery is simply defined as machinery that wraps and protects goods, and is indispensable in our daily lives.

Packing machinery is manufactured in consideration of the characteristics of each product to be packaged.

In particular, packing machinery used in the food industry, which is distributed on a daily basis and handles foodstuffs that have a significant impact on health. Upgrades are constantly being made to provide a higher level of functionality to keep pace with the daily evolution of packaging technology.

Uses of Packing Machinery

Packaging machinery is used in a wide variety of fields, and many manufacturers of familiar food products and sundries as well as pharmaceuticals who use packaging machinery day and night.

In addition, packaging machinery is used not only for “commercial packaging,” which is mainly for retail purposes, but also for “industrial packaging,” which is used to transport and store goods.

Furthermore, as the required functions of packaging machinery increase, such as in the food industry, it has become necessary to link it with the pre-processing of the goods to be packaged, and integration is being promoted along with higher functionality and multifunctionality.

Features of Packing Machinery

Packaging machinery is classified into vertical pillow wrapping machines and horizontal pillow wrapping machines according to the direction in which the product to be packaged is fed, as well as “top wrapping machines” that wrap the product from above and “boxers” that pack the product into cardboard boxes, among others.

In addition, blister packs, which have recently become the mainstream for pharmaceuticals such as tablets and capsules, as well as sundries, are packaged using a combination of a convex transparent resin and a backing paper, for which specialized machinery is used.

Packing machinery varies greatly depending on the item to be packaged. In the case of food packaging, the contents are vacuumed or gas-filled to prevent deterioration of the contents.

Isolation from external factors is especially important for packaging food products. External factors include oxygen and moisture in the air, sunlight, temperature, and microorganisms.

The packing machinery used for food products depends on the ability to minimize the effects of these external factors.

What Is a Spinner

A spinner is a machine that spins raw materials (natural fibers such as wool or chemical fibers) into yarn. Natural fibers are often spun from a single raw material, while synthetic fibers are sometimes spun from a mixture of natural and chemical fibers.

Spinning is generally done in the following order, depending on the raw material: blended cotton, combed cotton, woven cotton, spun cotton, spun yarn, and wound yarn.

Natural fibers are often spun from a single raw material, while synthetic fibers are sometimes spun from a mixture of natural and synthetic fibers, depending on the application.

Uses of Spinners

In spinning, natural and synthetic fibers are mixed in the blended cotton process, and the mixture is made to a uniform thickness, rolled, and then carded in the next process to make thicker twine.

In the kneading machine, the material made in the previous process is stretched while being homogenized, and then further stretched in the next coarse to make coarse yarn with a thickness of 5 to 8 mm dia.

The coarse yarn is further stretched and twisted to increase its strength, and then it is wound onto a bobbin to be made into a tube yarn. In the final winding machine, the yarn is finished and spun into cylindrical or conical shapes to complete the process.

Features of Spinners

The machines used and their purposes differ depending on the manufacturing process.

• Blended spinners
  After removing dust and other debris from the inside of the cotton, it is “wrapped” and formed into a sheet.
• Carding machine
  The mixed fibers of the wrap are then combed to align the fibers in a certain direction before being turned into yarn, which is then stretched and bound into a thick thread called a “sliver”. However, it remains fragile, easily breaking when pulled.
• Kneading machine
  About 8 to 10 slivers are bound together, and their thickness is adjusted as they are stretched. The result is called a “kneaded shino sliver,” which is still weak and will break if pulled.
• Rough spinners
  This machine stretches and twists the kneaded shino sliver to produce a coarse yarn,  and finally has a little strength.
• Spinners
  The coarse yarn is further twisted while being stretched and is finally completed as a tubular yarn, which is then wound onto a bobbin.

In the final “rewinding process,” the yarn wound on the bobbin is made into cylindrical “cheese” or corn-like “corn,” depending on the intended use, and the spinning process is completed.

What Is a Corrosion Inhibitor?

A corrosion inhibitor is used to prevent rust on metal products and metal parts.

Generally used on steel, the corrosion inhibitor is applied in liquid form directly to the object to protect the metal surface.

There are several types of corrosion inhibitors, depending on the product and application.

Uses of Corrosion Inhibitors

1. Liquid Corrosion Inhibitors (Water-Soluble or Oil-Soluble)

Liquid corrosion inhibitors are used when applied directly to the target metal or added to a solution. Typical examples of its use include application to the surface of steel plates, application to springs (such as piano wires), addition to press oil and cutting oil, and application to other steel parts.

2. Vaporizable Corrosion Inhibitors

Vaporizable corrosion inhibitors prevent rust by forming a film of inhibitors on the surface of metal parts. The rust-preventive ingredients that form the film gradually evaporate, preventing the metal from reacting with moisture and oxygen in the atmosphere, which causes rust. Volatile rust inhibitors are used in the form of corrosion inhibitors paper or corrosion inhibitors film coated or impregnated on film or paper. By wrapping metal parts with anticorrosive paper or anticorrosive film, or by including volatile anticorrosive agents, the anticorrosive agent will gradually evaporate and exert its anticorrosive effect.

Principle of Corrosion Inhibitors

Figure 1. Mechanism of rust formation

Corrosion inhibitors inhibit rust by forming a protective film on metal surfaces that inhibits contact with water and oxygen, which causes rust.

Oxygen from the air dissolves in the water film, but the concentration of the dissolved oxygen differs between the water film surface and the metal surface. 

Since rust occurs when metals come into contact with moisture and oxygen in the air, corrosion inhibitors are used to prevent rust from occurring.

Types of Corrosion Inhibitors

Figure 2. Typical rust inhibitors

Corrosion inhibitors are classified into three types based on their chemical properties: water-soluble corrosion inhibitors, oil-soluble corrosion inhibitors, and vaporizable corrosion inhibitors.

1. Water-Soluble Corrosion Inhibitors

Figure 3. Rust suppression mechanism of water-soluble rust inhibitor

Water-soluble corrosion inhibitors are corrosion inhibitors that dissolve in water. They are classified into oxidized film type, precipitated film type, and adsorbed film type according to the type of film formed. Typical compounds are chromate, molybdate, polymerized phosphate, and mercaptobenzothiazole. Surfactant-type corrosion inhibitors also fall into the category of water-soluble corrosion inhibitors, and the structure of such compounds has both polar and hydrophobic groups in the molecule. The polar groups in the molecule adsorb on the metal surface and the hydrophobic groups cover the metal surface. The hydrophobic group has the property of excluding water molecules, thus reducing the formation of rust. 

2. Oil-Soluble Corrosion Inhibitors

Oil-soluble corrosion inhibitors are low-polarity corrosion inhibitors that are soluble in oil and form an adsorption-type film. The structure of an oil-soluble rust inhibitor has both polar groups and hydrocarbon chains in the molecule. The hydrocarbon chain has a sufficiently long structure so that the compound as a whole is highly lipophilic. When applied to a metal surface, the polar groups adhere to the metal surface, while the hydrocarbon chains, which exhibit lipophilic properties, cover the metal surface. These hydrophobic chains retain oil components, so the metal surface is covered with a thin layer of oil.

Typical compounds are petroleum sulfonates and sorbitan esters.

3. Evaporative Corrosion Inhibitors

Vaporizable corrosion inhibitors are corrosion inhibitors that vaporize slowly at room temperature and pressure. The vaporized rust inhibitor fills the atmosphere and forms a thin film on the metal surface, thereby producing a rust-preventive effect. Typical compounds include diisopropylammonium nitrite and dicyclohexylammonium nitrite.

Other Information on Corrosion Inhibitors

Other Materials With Anticorrosive Properties

The following groups of compounds also have rust-preventive properties and are widely used:

1. Plastics
Plastics are sprayed on metal surfaces or immersed in metal to coat them, thereby preventing the formation of rust. Based on their applications and characteristics, they are classified into two types: coated and hot dipped. In the case of the paint type, the film formed is relatively thin and is easy to peel off, and in the case of the hot dipping type, the film is thicker than the coated coating.

2. Desiccant
Silica gel is a typical example of a desiccant widely used to remove moisture from packaging.

3. Oxygen absorber
Oxygen absorbers are used to prevent rust from occurring by fixing oxygen in the packaging. Iron powder, which is inexpensive and readily available, is commonly used.

4. Corrosion inhibitor
These are compounds that adsorb on metal surfaces to form their film to inhibit the generation of rust. A wide range of compounds falls under this category, including various inorganic salts and organic acids. Examples include various chromates, carboxylic acids, amine salts, and esters.

5. Chelating agents
A type of compound that forms complex salts on the surface of ferrous metals to prevent rust formation; typical examples are EDTA, gluconic acid, NTA, and HEDTA.

What Are Rubber Vibration Isolators?

Rubber vibration isolators are rubber products that use the elasticity of rubber to reduce the transmission of vibration. It is sometimes called cushioning rubber or insulator.

Purpose of Rubber Vibration Isolator

Rubber vibration isolators are used for two main purposes:

The first is to prevent the transmission of vibrations or shocks caused by the operation of equipment to the outside.

The second is to prevent external vibrations from affecting the characteristics of equipment, such as precision instruments.

Types of Rubber Vibration Isolator and Examples of Use

Rubber vibration isolators come in a variety of shapes and sizes, including plates, and cylinders.

By placing rubber vibration isolators under generators, outdoor units of air conditioners, compressors, etc., vibrations emitted by these devices can be mitigated and transmission of vibrations to the installation base or location can be suppressed.

In addition, those integrally molded with bolts, are highly versatile and can be easily installed as long as the equipment has a bolt receptor.

In addition to bolts, there are also those integrally molded with a flange and those with a cylindrical hollow interior. Some are shaped to be attached to the mounting surface of a motor, while others are used for vibration-damping applications in the direction of the rotational axis.

For precision equipment such as optical system units that are affected by external vibrations, rubber vibration isolators are used to hold the equipment on the installation surface so that it is not affected by external vibrations.

Criteria for Selecting Rubber Vibration Isolator

1. Natural Frequency

To isolate vibration, the relationship with the natural frequency of the structure is important.

The natural frequency is the frequency at which the structure vibrates most when driven by the equipment itself or by external vibrations. The natural frequency is expressed as a unit of frequency in Hz (hertz), and the structure does not respond well and does not vibrate significantly when driven at a frequency far outside the natural frequency or when shaken from the outside. Therefore, when a structure is held in place by rubber vibration isolators, the transmission of vibration can be effectively mitigated by keeping the natural frequency of the rubber vibration isolators far away from the target vibration (i.e., the vibration of the structure being driven or the vibration of the location where it is installed).

This is the same when using the rubber as a cushioning material or as a soundproofing material.

2. Factors That Determine the Characteristics of Rubber Vibration Isolator

As mentioned above, rubber vibration isolators use the elasticity of rubber to suppress the transmission of vibration. Their characteristics are determined by the spring constant, which expresses elasticity.

By selecting the appropriate shape and dimensions, the spring constant of rubber vibration isolators can be set to any value in the up/down, left/right, and front/rear directions. It is this spring constant that causes the natural frequency to vary as mentioned above.

3. Material

NR (natural rubber) and SBR (styrene rubber), which are commonly used for rubber vibration isolators, generate little heat due to vibration and are highly durable.

However, depending on the temperature conditions of the environment in which the product is used (high or low-temperature environment), we recommend the use of CR (chloroprene rubber) rubber vibration absorbers & isolators with high weather resistance.

In addition, when oil resistance is required, NBR (nitrile or urethane rubber vibration absorbers & isolators) are suitable.

What Is an Anti Vibration Pad?

An anti vibration pad is used to suppress vibration in a variety of equipment that generates vibration.

They are made of materials such as natural rubber and function simply by being placed under machinery. They are also cost-effective.

Many anti vibration pads have special patterns of irregularities on the surface, which reduces the spring constant and improves vibration control even if the pad is thin.

They can also be cut to the appropriate size, so they can be easily installed at the work site to suit the situation.

Uses of Vibration Absorbing & Isolating Pads

Equipment that generates vibration includes refrigerators and heat pumps. These are caused by the compression motion of pistons.

Machine tools such as milling machines and lathes also generate vibration, which can affect the accuracy of the workpiece.

In blowers and pumps, the blades rotate to discharge or suction gases. Vibration can occur during the collision of the blades with the gas and the subsequent compression process.

Anti vibration pads are also used to suppress vibration in printing equipment, sewing machines, generators, etc.

Principle of Vibration Absorbing & Isolating Pads

Many machines generate vibration and noise during their operation.

Refrigeration equipment and heat pumps use a gas compressor called a compressor. The piston moves back and forth during the compression process to change the gas to a high-temperature, high-pressure gas, which can easily cause vibration and noise.

Vibration also occurs in machine tools. For example, when cutting a surface on a milling machine or lathe, vibration can cause the surface to become uneven, which may prevent flat machining (called chattering vibration).

These vibrations, if they continue for a long time, can accumulate damage to the machine and reduce its original functionality. Physical damage can occur not only to the machine itself, but also to its surroundings.

Anti vibration pad can absorb these vibrations and impacts by utilizing the elasticity of rubber. They have a relatively long lifespan and provide stable anti-vibration and soundproofing performance.

Most are manufactured from natural or recycled rubber. Typical thicknesses are as thin as 10 mm to 20 mm, and they can be cut into large or arbitrarily sized pieces.