PMPO versus RMS

Root mean square (also known as RMS) is a measurement used to acquire the output values of the Power Outputs. It is also known as the most accurate way of garnering these measurements. The RMS is also known as the quadratic mean. In this case, it is used to measure amplifier power. It is used in conjunction with the electric efficiency of an electronic amplifier, and is a way to measure the ratio of mean (or average) output power to mean (or average) output power.

Torque Induction Motor

The input power to a three-phase induction motor is given by

Output power can be found by subtracting the losses from the input power

Losses

• Stator Copper Loss. The stator resistive losses 

Slip Induction Motor

Induction motors

These motors are probably the simplest and most rugged of all electric motors. They consist of two basic electrical assemblies: the wound stator and the rotor assembly.
The rotor consists of laminated, cylindrical iron cores with slots for receiving the conductors. On early motors, the conductors were copper bars with ends welded to copper rings known as end rings. Viewed from the end, the rotor assembly resembles a squirrel cage, hence the name squirrel- cage motor is used to refer to induction motors. In modern induction motors, the most common type of rotor has cast-aluminum conductors and short-circuiting end rings. The rotor turns when the moving magnetic field induces a current in the shorted conductors. The speed at which the magnetic field rotates is the synchronous speed of the motor and is determined by the number of poles in the stator and the frequency of the power supply.
 

INDUCTION MOTOR

Induction motors are electric motors of alternating current (ac), the most widely used Penamaannya stems from the fact that it works based on the induction motor's magnetic field into statornya stator, rotor motors where the flow is not obtained from a particular source, but it is a current induced as a result of relative difference between the spin rotor with rotating field (rotating magnetic field) generated by the stator currents.
Induction motors are widely used in everyday life both in industry and in households. Induction motors are commonly used 3-phase induction motor and 1-phase induction motor. 3-phase induction motor operated at 3-phase power system and is widely used in various industrial fields, while the 1-phase induction motor operated at 1-phase power systems are widely used, especially in use for household appliances such as fans, refrigerators , water pumps, washing machines and so forth because the 1-phase induction motor has a low output power.

The construction of the induction motor

Power-Factor Correction Using Synchronous Motor

For a constant load, the power factor of a synchronous motor can be varied from a leading value to a lagging value by adjusting the DC field excitation (Figure bellow). Field excitation can be adjusted so that PF = 1 (Figure a). With a constant load on the motor, when the field excitation is increased, the counter EMF (VG) increases. The result is a change in phase between stator current (I) and terminal voltage (Vt), so that the motor operates at a leading power factor (Figure b). Vp in Figure  is the voltage drop in the stator winding’s due to the impedance of the windings and is 90o out of phase with the stator current. If we reduce field excitation, the motor will operate at a lagging power factor (Figure c). Note that torque angle, a, also varies as field excitation is adjusted to change power factor.

Synchronous motors are used to accommodate large loads and to improve the power factor of transformers in large industrial complexes.

Know Types of Motors Based on Rotation

Motor is a device that converts electrical energy into mechanical energy. The working principle of the electric motor is using the Lorentz force, the force that makes an electrically charged wire moving if brought near to a homogeneous magnetic field. 

 

Commutator and Slip Ring

In principle commutator insulation should be recessed below the surface of the segments, unless hard carbon brushes are used. Segment edges should be bevelled to ensure on the one hand proper communication and on the other to avoid high brush wear or brush breakage.

 Commutator

 Slip Ring

Electric motor

In the article "The classification of electrical machinery, electric motors including into the category of dynamic electric machine and it is an electromagnetic device that converts electrical energy into mechanical energy. Mechanical energy is used for, for example, rotating impeller pump, fan or blower, compressor moving, lifting materials, etc. in the industry and is also used in household electrical appliances (such as: mixers, electric drill, electric fan).
The electric motor is sometimes called the "work horse" of his industry, because it is estimated that motors use about 70% of the total electrical load in the industry.
Mechanism of action for all types of electric motors are generally similar (Figure 1), namely: • An electric current in a magnetic field will exert a force. • If the wire that carries the flow is bent into a circle / loop, then both sides of the loop, ie at right angles to the magnetic field, will gain force in the opposite direction. • Couple style produces power play / torque to rotate the coil. • motors have several loops on dinamonya to provide a more uniform torque and the magnetic field generated by the electromagnetic structure of the so-called field coils.
In understanding an electric motor, it is important to understand what is meant by the motor load. Expense refers to the output power play / torque in accordance with the required speed. Expenses can generally be categorized into three groups: • constant torque load, is the burden which the demand for its energy output varies with the speed of operation, but its torque does not vary. Examples of constant torque loads are conveyors, rotary kilns, and the constant displacement pump. • Expenses with variable torque, is the load torque that varies with the speed of operation. Examples of variable torque loads are centrifugal pumps and fans (torque varies as the square of velocity). • Expenses with constant energy, is the load torque change with demand and inversely proportional to speed. Examples for the constant power load is machine tools. 

Figure 1. Working Principles of Electric Motors.

DC Generator

DC generator is a device that converts electrical machine dynamic mechanical energy into electrical energy. DC generator produces DC current / direct current. DC generator can be divided into several types on the basis of a series of winding magnet or amplifier eksitasinya to anchor (anchor), types of DC generators, namely: 1. Generators separate amplifier 2. Shunt generator 3. Compound generator
1. DC Generator Construction
In general, the DC generator is made by using a permanent magnet with a 4-pole rotor, digital voltage regulators, protection against overload, excitation starters, rectifiers, bearings and generator house or the chassis, and the rotor. Figure 1 shows a cross-sectional images DC generator construction. DC generator consists of two parts, the stator, namely the DC machine is silent, and the rotor, which is part of a rotating DC machine. Stator part consists of: the framework of the motor, the stator windings, brush charcoal, bearing and terminal boxes. While the rotor consists of: commutator, rotor windings, the fan rotor and the rotor shaft.

Brushes, Commutator and Armature

The "flipping the electric field" part of an electric motor is accomplished by two parts: the commutator and the brushes.

 The diagram at the above shows how the commutator and brushes work together to let current flow to the electromagnet, and also to flip the direction that the electrons are flowing at just the right moment. The contacts of the commutator are attached to the axle of the electromagnet, so they spin with the magnet. The brushes are just two pieces of springy metal or carbon that make contact with the contacts of the commutator

Universal Motor

Types

A universal motor can be manufactured in two different ways.

· Non-compensated type with concentrated poles

· Compensated type with distributed field.

The compensated type is preferred for high power rating appliances and the Non-compensated for low power rated appliances. Both the compensated and Non-compensated have construction similar to that of a DC series motor.

Non-Compensated motor

Brushless DC motor (DC motor without brush)

Brushless DC motors were developed from conventional brushed DC motors with the availability of solid state power semiconductors. So, why do we discuss brushless DC motors in a chapter on AC motors? Brushless DC motors are similar to AC synchronous motors. The major difference is that synchronous motors develop a sinusoidal back EMF, as compared to a rectangular, or trapezoidal, back EMF for brushless DC motors. Both have stator created rotating magnetic fields producing torque in a magnetic rotor.
Synchronous motors are usually large multi-kilowatt size, often with electromagnet rotors. True synchronous motors are considered to be single speed, a submultiple of the powerline frequency. Brushless DC motors tend to be small– a few watts to tens of watts, with permanent magnet rotors. The speed of a brushless DC motor is not fixed unless driven by a phased locked loop slaved to a reference frequency. The style of construction is either cylindrical or pancake. (Figures and below)

Cylindrical construction: (a) outside rotor, (b) inside rotor.

DC Electric Motor

In any electric motor, operation is based on simple electromagnetism. A current-carrying conductor generates a magnetic field; when this is then placed in an external magnetic field, it will experience a force proportional to the current in the conductor, and to the strength of the external magnetic field. As you are well aware of from playing with magnets as a kid, opposite (North and South) polarities attract, while like polarities (North and North, South and South) repel. The internal configuration of a DC motor is designed to harness the magnetic interaction between a current-carrying conductor and an external magnetic field to generate rotational motion.
Let's start by looking at a simple 2-pole DC electric motor (here red represents a magnet or winding with a "North" polarization, while green represents a magnet or winding with a "South" polarization).

Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator, commutator, field magnet(s), and

Synchronous condenser in Electrical Power

Synchronous motors load the power line with a leading power factor. This is often usefull in cancelling out the more commonly encountered lagging power factor caused by induction motors and other inductive loads. Originally, large industrial synchronous motors came into wide use because of this ability to correct the lagging power factor of induction motors.

Capacitor Start

A three phase motor may be run from a single phase power source. (Figure below) However, it will not self-start. It may be hand started in either direction, coming up to speed in a few seconds. It will only develop 2/3 of the 3-φ power rating because one winding is not used.

3-φmotor runs from 1-φ power, but does not start.

The single coil of a single phase induction motor does not produce a rotating magnetic field, but a pulsating field reaching maximum intensity at 0^o and 180^o electrical. (Figure below)

 Single phase stator produces a nonrotating, pulsating magnetic field.

Single Phase to Three Phase Converter

Phase converters are used to convert the single phase power to three phase power. Three phase power is a popular way of transmitting electricity. The power plant that generates power, produces three different phases of electricity simultaneously. What is three phase power? Have you ever wondered why three? And why not two or four? The answer to this question is simple! These three phases are 120 degrees offset from each other. The three phase power requires four wires, three for the three phases and one for neutral. There are three phases because in a 360 degree cycle, there are three instances when the power waveform has a peak value. These values are shifted by an angle of 120 degrees. Usually, the utility companies provide earth as a ground connection.

Three Phase Conversion

Three phase converters are suitable for all the applications listed above. They can run one or many motors. They can be compared with other single to three-phase converters available worldwide, except they electronically switch 600 % rated power for up to 10 seconds and need no maintenance because they have no electromechanical contacts.

Three phase converters are capable of starting many motors simultaneously, even under load. Each motor will reach full speed in the shortest possible time. Motors also maintain their speed when momentarily overloaded.

This unique converter copes well with the most difficult applications: Metal lathes without clutches, hydraulic systems, refrigeration units, wheel balancers, older types of compressors. Three phase a will cope with start-stop operation, with forward-reverse and with electric brakes.

Three phase converter can be used with Variable Speed Drives.

Three phase converter installation

Install a single-phase industrial wall switch-socket combination. Connect your new converter. Now you have three-phase power for all your electric motor and machine tool requirements.

Motor speeds are constant as with a three-phase supply. Starting motors draw high currents. Three phase converter a will produce these currents in order to maintain output voltages. This will draw high input currents for a short time. On the single phase supply side it pays to install heavy cables. This will minimise voltage drop.

Installation instructions and service schematics are provided with each converter. A simple block diagram is shown below.

Basic Rectifier Circuit

Now we come to the most popular application of the diode: rectification. Simply defined, rectification is the conversion of alternating current (AC) to direct current (DC). This involves a device that only allows one-way flow of electrons. As we have seen, this is exactly what a semiconductor diode does. The simplest kind of rectifier circuit is the half-wave rectifier. It only allows one half of an AC waveform to pass through to the load.

 

Ground-Fault Relay

To be competitive, some electrical contractors often supply low-voltage (LV) service entrance switchboards and switchgear that meet the minimum safety requirements of the National Electrical Code (NEC). The Code stipulates that a ground-fault relay must be installed on the service entrance for services with a rating higher than 1,000A. This relay shall be set for no more than 1,200A, and it shall trip the service entrance breaker.
As related to safety, this is a great improvement over earlier requirements of the Code, which did not call for any ground-fault relay. However, it must be noted that this level of ground sensing and time delay protection arrangement provides limited coordination with any possible downstream protective devices. As a result, when the main service entrance device trips the entire building suffers a blackout.
So what can you do to improve the overall protection and coordination of the power delivery system? Let’s take a look at some other options you have to improve system performance and better serve your customer.
As per Code requirements, all 3-phase, 4-wire circuits, where the neutral is distributed and used for the load(s), must be solidly grounded. As a matter of habit, many designers and installers also solidly ground 3-phase, 3-wire systems. In such systems, the ground-fault sensing relays, which are installed at various levels throughout the distribution network, are time-current coordinated.
Where there are multiple levels (i.e., zones) in the power system, there is a need for coordination of the zones so that, whenever possible, the higher levels are unaffected by downstream faults. The branch circuits are like tree branches, and all of the relays will “see” the fault current in a particular branch when the fault is downstream.

Grounding Systems

Should I install an ungrounded, solid, or high-resistance grounding system? That is the question asked by many designers and installers. The answer to this question depends on many factors. To make the correct decision, you must completely understand the pros and cons of each type of system. But first, you must also understand the different types of faults that can occur on your system and in what frequency they may appear.