The pitch or coil span factor is defined as the ratio of actual coil voltage to the coil voltage for a full-pitch coil.
Hence, pitch factor, KP = Vector sum of induced emf per coil/ Arithmetic sum of induced emf per coil...
December 3, 2011
November 29, 2011
How to convert electrical energy to infrared energy or to microwave energy?
To convert to IR, use an IR lamp, aka heat lamp. IR is heat energy. To convert to microwave, you need a magnetron and a high voltage power supply, as is found in a microwave oven.
For the reverse, it is more difficult....
November 27, 2011
Describe the Application of Synchronous Motors
Synchronous motors are usually used in large sizes because in small sizes they are costlier as compared with induction machines. The principal advantages of using synchronous machine are as follows:
–Power factor of synchronous machine can be controlled very easily by controlling the field current....
What is Synchronous Motor?
A synchronous motor is the same physical machine as a generator, except that the direction of real power flow is reversed...
What are the Advantages of Parallel operation of synchronous generators?
There are several major advantages to operate generators in parallel:
Several generators can supply a bigger load than one machine by itself.
Having many generators increases the reliability of the power system.
It allows one or more generators to be removed for shutdown or preventive maintenance.
...
What is Synchronous Generator?
Synchronous generators or alternators are used to convert mechanical power derived from steam, gas, or hydraulic-turbine to ac electric power.
Synchronous generators are the primary source of electrical energy we consume tod...
November 25, 2011
What is synchronous Condenser? Where and why it is used?
An overexcited synchronous motor running at no- load and used for power-factor correction is called synchronous condenser. It is also called synchronous capacitor.
It is used in a large system where the use of static capacitor is inefficient and expensive. It is used for power-factor correction...
November 22, 2011
Why the induction motor never runs at synchronous speed?
If rotor & stator have same speed, no relative motion
slip zero, no voltage induce in rotor
current zero, torque zero&nb...
Write down the significance of the name ‘induction’ in case of induction motor.
The supply is connected to the stator and the rotor received power by induction caused by stator rotating flux, hence the motor obtains its name –induction mot...
Why induction motor treated as a rotating transformer?
Transformer has two sides: primary & secondary.
Transformer transforms energy from primary to secondary by induction.
Similarly, Induction motor has primary (stator) & secondary (rotor).
Voltage is induced in secondary by rotating flux of const. magnitude i.e the process of induction.
Thus induction motor treated as a rotating transformer...
October 13, 2011
What is Phase and Phase Difference?
Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.
Phase difference is the difference, expressed in electrical degrees or time, between two waves having the same frequency and referenced to the same point in time...
September 28, 2011
What are losses of Transformer? Draw an equivalent circuit of Transformer.
Losses of TransformerThe power losses in a transformer are of two types, namely;1. Core or Iron losses 2. Copper losses
These losses appear in the form of heat and produce (i) an increase in temperature and (ii) a drop in efficienc...
September 25, 2011
What is the difference between a transformer, a converter and a power supply?
Transformer
A Transformer is an electrical device by which alternating current of one voltage is changed to another voltage using coils. There are several different types, but they all basically do the same thing - change the voltage. They are usually heavy for their size due to the weight of the coils (size and weight depends on their rating).
Converter
A Converter is an electronic device that is used in some cases instead of a transformer. The converter doesn’t actually lower the voltage, but rather delays each electrical cycle making...
What is the difference between 3 phase and single-phase electricity?
I suppose the textbook definition would be something like this:
A phase is the factional part of the period of a sinusoidal wave, usually expressed in electrical degrees.
A single-phase circuit is an alternating-current using only one, sine wave type, current flow. A three-phase circuit consists of three different sine wave current flows, different in phase by 120 degrees from each other.
Now let's have the more practical, "down to earth" definition - something that the average homeowner would at least have a chance of understanding:
Single...
September 15, 2011
Discuss basic principles of DC generator, AC generator (Alternator) & Motor.
DC Generator PrincipleAn electrical generator is a machine which converts mechanical energy (or power) into electrical energy (or power)....
September 13, 2011
Define power factor. What are ways to improve power factor & describe them with necessary diagrams.
Definition of Power Factor:
The cosine of the angle between voltage and current in an AC circuit is known as power factor.
Or
The power factor of a circuit can be defined in one of the following three ways:
Power factor = cos ∅ = cosine of the angle between V and I
Power factor = R/Z=Resistance/Impedance
Power factor = (VIcos ∅)/VI=(Active Power)/(Apperant Power)
Ways to Improve Power Factor:
Power Factor is a number between...
September 12, 2011
10 Interview Questions and Answers on Transformers - Part-1
Figure: Power transformer over-excitation condition caused by decreased frequency; flux (green), iron core's magnetic characteristics (red) and magnetizing current (blue).
1. How is magnetic leakage reduced to a minimum in commercial transformers?
By interleaving the primary and secondary windings.
2. Mention the factors on which hysteresis loss depends?
(i) Quality and amount of iron in the core
(ii) Flux density and
(iii)...
Why Transformer Rating in KVA instead of KW ?
As seen, Cu loss of a transformer depends on current and iron loss on voltage. Hence, total
transformer loss depends on volt-ampere (VA) and not on phase angle between voltage and current
i.e. it is independent of load power factor. That is why rating of transformers is in kVA and not in kW.
Another Answer:
There are 2 losses in transformer. One is copper loss which depends on current and the other is iron loss which depends on voltage. These two factors are not affected by the power factor. This is why transformers are rated in KVA and not...
September 10, 2011
What do you mean by real, reactive & apparent power?
a) Real Power (P)It is the power which is actually dissipated in the circuit resistance. Also called Active Power.
Measured in Units of Watts
b) Reactive Power (Q)It is the power developed in the inductive reactance of the circu...
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