Friday, 4 October 2013

Interview Questions for Electrical Engineering freshers

1. What's electric traction?
Traction implies with the electric power for traction system i. e. for railways, trams, trolleys etc. electric traction implies use of the electricity for all these. Now a day, magnetic traction is also utilised for bullet trains. Essentially dc motors are utilized for electric traction systems.

2. What is “pu” in EE?
Pu stands for per unit in power system. (pu = actual value/ base value)

3. Define stepper motor. What is the use of stepper motor?
 The motor which work or act on the applied input pulse in it, is called as stepper motor.This stepper motor is under the category of synchronous motor, which often does not fully depend of complete cycle. It likes to works in either direction related to steps. for this purpose it mainly used in automation parts.

4. What is a differential amplifier? Also, explain CMRR.
Differential Amplifier: The amplifier, which is used to amplify the voltage difference between two input-lines neither of which is grounded, is called differential amplifier. This reduces the amount of noise which is injected into the amplifier, because any noise appearing simultaneously on both the input-terminals as the amplifying circuitry rejects it being a common mode signal.
CMRR: It can be defined as the ratio of differential voltage-gain to common made voltage gain. If a differential amplifier is perfect, CMRR will be infinite because in that case common mode voltage gain would be zero.

5.  What is use of lockout relay in ht voltage?
 A lock-out relay is generally placed in line before or after the e-stop switch so the power can be shut off at one central location. This relay is powered by the same electrical source as the control power which is operated by a key lock switch. The relay itself may have up to 24 contact points within the unit itself. This allows the control power for multiple machines to be locked out by the turn of a single key switch.

6. How can you start-up the 40w tube lite with 230v AC/DC without using any choke/Coil?
 It's possible with Electronic choke. otherwise it's not possible to ionize the particles in tube. light, with normal voltage.

7. What types domain of Laplace transforms? What behavior can Laplace transform predict how the system work?
Types domain of Laplace transforms is s-domain, Laplace transforms provide a method to find position, acceleration or voltage the system will have.

8. In the magnetic fluxes, what is the role of armature reaction?
 The armature flux has an important role for the running condition. This armature flux can oppose the main flux or it may support the main flux for better running condition. This effect of supporting and opposing of main flux to armature flux is called armature reaction.

9. Explain thin film resistors and wire-wound resistors
Thin film resistors- It is constructed as a thin film of resistive material is deposited on an insulating substrate. Desired results are obtained by either trimming the layer thickness or by cutting helical grooves of suitable pitch along its length. During this process, the value of the resistance is monitored closely and cutting of grooves is stopped as soon as the desired value of resistance is obtained.
Wire wound resistors – length of wire wound around an insulating cylindrical core are known as wire wound resistors. These wires are made of materials such as Constantan and Manganin because of their high resistivity, and low temperature coefficients. The complete wire wound resistor is coated with an insulating material such as baked enamel

10. whats the one main difference between UPS & inverter ? And electrical engineering & electronics engineering ?
uninterrupt power supply is mainly use for short time . means according to ups VA it gives backup. ups is also two types : on line and offline . online ups having high volt and amp for long time backup with with high dc voltage.but ups start with v dc with 7 amp. but inverter is startwith v,24,dc to 36v dc and 0amp to 180amp battery with long time backup.


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