ISD

 Grounding

Grounding means to connect electrical equipment to a common reference ground or earth. 

These three systems are

• Ungrounded Systems
• Resistance Grounded Systems
• Solidly Grounded Systems

Types of grounding

Solidly grounded system

It is usually used in wye systems and this method is mostly used in the industrial, commercial and institutional power distribution system. in this method, the neutral is connected to the ground and thus it could ensure the neutral voltage is equal to the ground, by doing this method properly there won't be any phase to ground over-voltages.

Reactance grounding

In this method, a reactor is connected between the neutral point and the ground and the magnitude of the ground fault current can be reduced by changing the reactance. But this method is not used now because of the high transient voltage that appears during the ground fault condition

Resonant grounding

This method is also known as Peterson grounding because Peterson developed a coil which can limit the earth fault current in the undergrounded three-phase system. The coil will be in series with the line to the ground capacitance of each phase conductor and it is tuned to produce an impedance based on the series LC circuit and the coil will be adjusted according what it is connected.

Resistance grounding

The resistance grounding is divided into two types high and low resistance grounding, the high resistance grounding system is done by connecting a high resistance in between the neutral point of a low voltage transformer and the ground. The high grounding system is used for small and medium industry applications where continuous operation is needed during the fault condition

Shielding

Shielding is used both for immunity (protecting against external interference) and emission (preventing interference to be radiated).

Types

1. Braid Shield – The most common method of shielding, this can be accomplished by crossing layers of individual metal stands (typically copper or aluminum metal) over a cable core or an insulated conductor.

2. Serve or Spiral Shield – Spiral Shields can be manufactured by applying metallic strands in a helical fashion around a cable core or an insulated conductor.

3. Aluminum Foil Shielding Tapes – These tapes can be constructed in either single sided, dual sided or 100% aluminum configurations. This method allows 100% effective coverage and is an excellent shield for ESD problem applications.

4.Conductive Nylon Tapes – Although conductive mylar tape has problems with inconsistent conductivity, it is widely used for reducing turboelectric noise, especially in audio frequency applications.

5. Conductive Plastics – Conductive plastics have been used as shields and also as a means to reduce corona problems on very high voltage cables. Because of inherent inconsistent conductivity, these conductive plastics should be used only in conjunction with another shielding method.

6. Conductive Textiles – This new method employs textile threads that have been metal plated. These threads are then braided or served over the item to be shielded. It should be used only when flexibility warrants.

IP Ratings Explained

Protect your electrical enclosure and its contents by knowing where and how it will be used so that you can order one with the correct IP Rating.

The IP rating system was established by the International Electromechanical Commission (IEC), a worldwide organization for standardization. The object of the IEC is to promote International cooperation on all questions concerning standardization in the electrical and electronic fields. The IEC collaborates closely with the International Organization for Standards (ISO).

• IP54 - "limited dust tight" and protected against water spray in any direction
• IP65 - "dust tight" and protected against water projected from a nozzle
• IP67 - "dust tight" and protected against immersion between 15cm and 1 meter in depth
• IP68 - "dust tight" and protected against immersion.

The IP rating normally has two (but may have three) numbers:

1. Protection from solid objects or materials

2. Protection from liquids (water)

3. Protection against mechanical impacts (commonly omitted, the third number is not a part of IEC 60529)

voltage regulator

A voltage regulator is used to regulate voltage levels. 

Voltage regulator, any electrical or electronic device that maintains the voltage of a power source within acceptable limits. 

The voltage regulator is needed to keep voltages within the prescribed range that can be tolerated by the electrical equipment using that voltage.

Types of voltage regulators

•  Linear voltage regulators
• Switching voltage regulators

Linear voltage regulators

Linear voltage regulators are the original type of regulators use to regulate the power supplies. 

Switching voltage regulators

series voltage regulator uses a variable element placed in series with the load. 

By changing the resistance of that series element, the voltage dropped across it can be changed.

 And, the voltage across the load remains constant

LM2596

The LM2596 regulator is monolithic integrated circuit ideally suited for easy and convenient design of a step-down switching regulator (buck converter). It is capable of driving a 3.0 A load with excellent line and load regulation. This device is available in adjustable output version and it is internally compensated to minimize the number of external components to simplify the power supply design. Since LM2596 converter is a switch-mode power supply, its efficiency is significantly higher in comparison with popular three-terminal linear regulators, especially with higher input voltages.

The LM2596 operates at a switching frequency of 150 kHz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Available in a standard 5-lead TO-220 package with several different lead bend options, and D²PAK surface mount package.

The other features include a guaranteed ± 4% tolerance on output voltage within specified input voltages and output load conditions, and ± 15% on the oscillator frequency. External shutdown is included. featuring 80 μA (typical) standby current. Self protection features include switch cycle-by-cycle current limit for the output switch, as well as thermal shutdown for complete protection under fault conditions.

Features

• Adjustable Output Voltage Range 1.23 V-37 V

• Guaranteed 3.0 A Output Load Current

• Wide Input Voltage Range up to 40 V

• 150 kHz Fixed Frequency Internal TTL Shutdown Capability

Oscillator

• Low Power Standby Mode, typ 80 μA

• Thermal Shutdown and Current Limit Protection

• Internal Loop Compensation

• Moisture Sensitivity Level (MSL) Equals 1

• Pb-Free Packages are Available

Applications

• Simple High-Efficiency Step-Down (Buck) Regulator

 • Efficient Pre-Regulator for Linear Regulators

• On-Card Switching Regulators

• Positive to Negative Converter (Buck-Boost)

• Negative Step-Up Converters

• Power Supply for Battery Chargers

NEMA Std and type 

NEMA is National Electrical Manufacturing Association.

in an organisation developed to form techmital std for manufacturing of Electrical Equipment and

medical imaging equipment. NEMA Works to set industry Std for safety, innovation,

inter operability, Environment and nan ketenrichine nt medical imaging equipment.