Working Principle Of Inductive Sensor

By applying a voltage to the oscillator coil an alternating inductive field is created in front of the active surface of the unit.

When a metallic object (steel, aluminum, copper, brass etc.) enters this field from any direction and the state of the oscillator is modified until the threshold of the trigger is inverted this induces a change in the final stage and the subsequent command of an external load. The intervention distance depends on the type of metal and as described earlier, in the reduction factors. All the sensors are protected against inversion of polarity and electrical disturbances of inductive sources and can be supplied with short circuit protection in the D.C. version. The main advantages offered by proximity sensors in relation to normal limit switches are mainly unlimited duration as they have no moving parts (wheels, springs etc.) lack of maintenance requirement and elimination of possible false contacts due to contact movement.

Quality Systems (a Reference to IS0 9000)

Making of the Quality Systems

Many countries have framed guidelines and standards. The earliest standard was issued in 1959 by the US Department of Defense for large contracts (MIL-Q 9858. ‘Quality program requirements’). The long interval between Taylor‘s description of Quality Management in 1911 until 1959. When the US Defense Department laid down its quality requirements for the first time, was perhaps due to an increase in global interest that developed only in the late 1950s. Since then, there has been a continuous application of these standards to contractors and manufacturers worldwide. For civilian use in the United States. ANWASQC. Standard C and ZI, I5 were published in 1968. Since then, many countries and large organizations have been publishing their own quality control systems. For civilian reference, ‘A Guide to Quality Assurance’ was first published in 1972 (BS 4891). This was soon replaced by BS 5 179, ‘Guide to Operation and Evaluation of Quality Assurance Systems’. This was upgraded by BS 5750 in six parts. To ensure consistency in all standards and to make them universal a technical committee, TC/I 76, of the International Standards Organization (ISO), Switzerland, was entrusted with the task of drawing up such a set of standards. They have by now introduced the following standards:

IS0 8402

Quality Vocabulary.

IS0 9000

Quality Management and Quality Assurance Standard. Guidelines for selection of Standards in the series and use of the same for the management of quality systems.

IS0 9001

Model for Quality Assurance in Design or Development, Production. Installation and Servicing.

Applicable to those who design, produces, install and service their products or carry out such activities.

IS0 9002

Model for Quality Assurance in production, installation and servicing.

Applicable to those who make their products on the basis of some proven designs, or work as ancillaries for standard products.

IS0 9003

Model for Quality Assurance in Final Inspection and Test.

Applicable to those who are engaged in third-party inspection and testing.

IS0 9004

Quality Management and Quality System Elements - Guidelines.

Applicable to quality assurance for services, such as hotels and hospitals etc.

All these standards have since been adopted by the member countries as their national standards, fully or in slightly modified forms, to suit their own requirements and working conditions. These standards define and clarify the quality norms and aim at in-house quality disciplines, to automatically and continually produce a product, provide a service or program to the stipulated specifications, quality norms and customer needs. They guarantee a product or service with a minimum quality. The envisaged quality systems thus aim at a work culture that pervades all those involved in different key activities or processes, to achieve the desired goal through carefully evolved systems.

Maintenance of bearings

Reasons for high bearing temperature

This may be due to

• Excessive quantity of grease causing churning
• Inadequate grease due to deterioration or leakage
• Misalignment, causing friction and excessive axial forces
• Loose fit of the bearing housing, causing both inner and outer races of the bearing to rotate inside the housing
• Corrosion or the presence of foreign matter in the bearing.

Any of the above reasons may result in noise and an increase in temperature and must be corrected. Critical installations such as a refinery, a petrochemical plant, a chemical plant or a petroleum pipeline may require special precautions and control to avert any excessive heating of the bearings, which may become fire hazards. For these installations, bearing temperature detectors with a relay and alarm facility may also be installed in the control circuit of the switching device to give warning or trip the motor if the temperature of the bearing exceeds the preset safe value.

Maintenance of bearings

Grease may leave skin effect on the races of the bearings if the motor is stored idle for a long period. This may cause noise during operation and overheating of the bearings. After a long period of storage grease may also dry and crack, and produce these effects. To detect this, bearing covers may be opened and the condition of the grease and any skin effects checked. If such marks are visible, the bearings must be taken out and washed thoroughly in petrol or benzene to which is added a few drops of oil, and then re-greased with a recommended grade and quantity of grease. Quantities of grease above recommended levels may cause heat the same way as quantities below recommended levels.

Cleaning bearings

For cleaning bearings and bearing housings, before applying the grease, only the following fluids should be used: benzene, white petrol and benzole (white petrol is the most recommended).

How to Select a Transformer

Single Phase Encapsulated - 50 VA to 25 KVA

For all general loads, indoors or out, including lighting, industrial and commercial applications.

Units may be banked for three phase operation

Single Phase Ventilated – 15 to 100 KVA

For all general single phase loads, indoors or out, including lighting, industrial and commercial applications.

Three Phase Encapsulated – 3 to 75 KVA

For all general three phase loads, indoors or out, including lighting, industrial and commercial applications.

Three Phase Ventilated – 15 to 1000 KVA

For all general three phase loads, indoors or out, including lighting, industrial and commercial applications.

Totally Enclosed Non Ventilated – 15 to 500 KVA

Single and three phase designed for use in dirty environments.

Drive Isolation – 3 to 990 KVA

For industrial and commercial applications with SCR-controlled adjustable speed motor

drives, and AC adjustable frequency or DC drives.

Non-Linear Three Phase – 15 to 500 KVA

For electronic loads to meet non-linear load demands caused by modern office equipment.

For indoor and outdoor applications

Buck-Boost – 50 VA to 10 KVA

For correcting voltage line drops, landscape lighting, low voltage lighting, international voltage adaptation and motor applications. Buck-boost transformers do not compensate for fluctuating line voltages.

Industrial Control – 50 to 5000 VA

For control panels, conveyor systems, machine tooling equipment, commercial sewing

machines, pumping system panels, and commercial air conditioning applications.

Lighting – 100 to 1000 watts

For use with submersible fixtures including swimming pools, water fountains, low voltage circuits near water or other shock hazards. These transformers are not submersible. Single and three phase designed for use in dirty environments.

Motor Nameplate - Meaning and details

Understanding motor’s nameplate

You can fine a nameplate of a motor in motor body. Every essential data is given on this nameplate. Some times it’s difficult to understand, but it is very important. You need this data for maintenance, installation or change any kind of equipment. Engineers should concern about this data. The information of a motor nameplate is not same for all motor. Different manufacturers give different information. But most of the case, there are 15 essential information given on motor nameplate.

1. Voltage
2. Frequency
3. Phase
4. Current
5. Power factor
6. kW or Horsepower
7. Full-load speed
8. Efficiency
9. Duty
10. Insulation class
11. Maximum ambient temperature
12. Enclosure
13. Frame
14. Bearings
15. NEMA // Service factor

Standardize Circuit Symbols

Here is some Standardize Circuit Symbols:
Click on Image to Enlarge

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