Electrical Engineering

MCBs are classified according to tripping over range of fault current as follows:

• Type B MCB
• Type C MCB
• Type D MCB

Type B:

This type of MCB trips between 3 and 5 times full load current. Type B devices are mainly used in residential applications or light commercial applications where connected loads are primarily lighting fixtures, domestic appliances with mainly resistive elements. The surge current levels in such cases are relatively low.

Type C:

This type of MCB trips between 5 and 10 times full load current. This is used in commercial or industrial type of applications where there could be chances of higher values of short circuit currents in the circuit. The connected loads are mainly inductive in nature (e.g. induction motors) or fluorescent lighting.

Type D:

This type of MCB trips between 10 and 20 times full load current. These MCBs are use in specialty industrial / commercial uses where current inrush can be very high. Examples include transformers or X-ray machines, large winding motors etc.

Single phase power is one AC power source. Sometimes it is center-tapped (the term comes from the center-tap on the transformer secondary, which is grounded and called neutral) in which case it is called 120/240 VAC split phase, connectable as 120, 120, or 240. Sometimes, such as in Europe, it is 220 VAC, with one end grounded and (maybe?) called neutral. Sometimes, is is various voltages, one end grounded and called neutral, being one of three phases in wye configuration.

Three phase power is three AC power sources that are 120 degrees out of phase with respect to each other. In the wye configuration, you have three hots, and one common, grounded, neutral. In this case, the loads are connected between each hot and the neutral. In the delta configuration, you have three hots, with no neutral, though there is still an ultimate ground reference someplace upstream so as to limit the maximum phase to ground voltage. In this case, the loads are connected between each of the three pairs of hots.

In larger motors, you often have three phase delta, with a neutral. In this configuration, the motor is started in wye configuration, at 1/3 normal power, and then switched over to delta configuration once it reaches some percentage of normal operating speed.

Single phase power is used for residential and light commercial/industrial services. Three phase power is used for heavier commercial/industrial services.

In some intermediate services, you have a combined 120/240 VAC split phase, with 240 VAC three phase. While not in common use today, this configuration has one of the three phases center-tapped and providing a neutral, in what we call the quadraplex configuration. You have "residential style" 120/240 VAC with a neutral, and 240 VAC delta-only three phase. Wye is not supported, unless you use isolation transformers. This configuration can save the cost of a transformer. We used it in one of my previous employers, running the office building on the 120/240 VAC split phase, and running the light factory on the 240 VAC three phase, with the occasional 480 VAC three phase load begin supplied by 1:2 step up transformers.

A power inverter, or inverter, is an electrical device that changes direct current (DC) to alternating current (AC);[1] the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits.

Solid-state inverters have no moving parts and are used in a wide range of applications, from small switching power supplies in computers, to large electric utility high-voltage direct current applications that transport bulk power. Inverters are commonly used to supply AC power from DC sources such as solar panels or batteries.

The inverter performs the opposite function of a rectifier.

Because it has little compatments in the matiral what are full of air

Because its molecular structure doesn't provide enough free charge carriers to support an electric current.

The measure of how difficult it is for electrons to flow through a circuit is called resistance.

Another Answer

Resistance is not a measure of 'how difficult' it is for electrons to flow through a circuit. It is more accurate to describe it as a measure of whether a material can supportcurrent flow.

For example, it's incorrect to say that an insulator 'blocks' current flow. It's more accurate to say that it has an insufficient amount of charge carriers to support an electric current.

You just Calculate Size of Bus bar which has been mentioned below:

Example: Calculate Size of Bus bar having Following Details

• Bus bar Current Details:
• Rated Voltage = 415V,50Hz ,
• Desire Maximum Current Rating of Bus bar =630Amp.
• Fault Current (Isc)= 50KA ,Fault Duration (t) =1sec.
• Bus bar Temperature details:
• Operating Temperature of Bus bar (θ)=85°C.
• Final Temperature of Bus bar during Fault(θ1)=185°C.
• Temperature rise of Bus Bar Bar during Fault (θt=θ1-θ)=100°C.
• Ambient Temperature (θn) =50°C.
• Maximum Bus Bar Temperature Rise=55°C.
• Enclosure Details:
• Installation of Panel= Indoors (well Ventilated)
• Altitude of Panel Installation on Site= 2000 Meter
• Panel Length= 1200 mm ,Panel width= 600 mm, Panel Height= 2400 mm
• Bus bar Details:
• Bus bar Material= Copper
• Bus bar Strip Arrangements= Vertical
• Current Density of Bus Bar Material=1.6
• Temperature Co efficient of Material Resistance at 20°c(α20)= 0.00403
• Material Constant(K)= 1.166
• Bus bar Material Permissible Strength=1200 kg/cm2
• Bus bar Insulating Material= Bare
• Bus bar Position= Edge-mounted bars
• Bus bar Installation Media= Non-ventilated ducting
• Bus bar Artificial Ventilation Scheme= without artificial ventilation
• Bus bar Size Details:
• Bus bar Width(e)= 75 mm
• Bus bar Thickness(s)= 10 mm
• Number of Bus Bar per Phase(n)= 2 No
• Bus bar Length per Phase(a)= 500 mm
• Distance between Two Bus Strip per Phase(e)= 75 mm
• Bus bar Phase Spacing (p)= 400 mm
• Total No of Circuit= 3 No.
• Bus bar Support Insulator Detail:
• Distance between insulators on Same Phase(l)= 500 mm
• Insulator Height (H)= 100 mm
• Distance from the head of the insulator to the bus bar center of gravity (h)= 5 mm
• Permissible Strength of Insulator (F')=1000 Kg/cm2