Quiz on dc generator

 

1. A simple method of increasing the voltage of a DC generator is

A) to decrease the air gap flux density
B) to decrease the speed of rotation
C) to increase the length of armature
D) to increase speed of rotation

ANSWER= (D) to increase the speed of rotation
Explain:- emf proportion to speed

 

2. Dummy coil in a DC generator is used to reduce

A) Hysteresis losses
B) Mechanical unbalance
C) Armature reaction
D) to reduce emf

ANSWER= (B) Mechanical unbalance
Explain:- some slots without armature winding that is caused unbalance

 

3. In dc generator, the critical resistance is equal to resistance of the

A) Load
B) brush
C) filed
D) armature
ANSWER= (C) field
Explain:- if field resistance is high then field current is not produce flux so no Generate residual magnesium for build up voltage in case of dc shunt generator


 

4. Armature reaction At Full load of a large DC machine can be tested by

A) swinburne test
B) Brake test
C) shot circuit test
D) hopkinson test

ANSWER= (D) hopkinson test
Explain:- also know as back to back test used to find out Armature reaction , temperature rises in larger machine


 

5. The number of brushes in a commutator depends on

A) Amount of current to be collected
B) winding
C) speed
D) voltage

ANSWER= (A) Amount of current to be collected
Explain:-

■ ULN2003 Drive Circuit

 It is  a  NPN Darlington transistor array drive IC used to control multiple output. 

● This single IC can control 7 output from microcontroller, we can easily control output.

● A Darlington transistor (also known as Darlington pair) achieves very high current amplification by connecting two bipolar transistors in direct DC coupling so the current amplified by the first transistor is amplified further by the second one.

● The resultant current gain is the product of those two components of transistor. 

》FEATURES-

● It has 16 pin IC. Out of two ground and common pic IC.

● Contains 7 high-voltage and high current Darlington pairs

● Each pair is rated for 50V and 500mA

● Input pins can be triggered by +5V

● All seven Output pins can be connected to gather to drive loads up to (7×500mA) ~3.5A.

● Can be directly controlled by logic devices like Digital Gates, Arduino, PIC etc.

》 Circuit diagram-

》Application-

● drive the stepper motor 

● blinking the bulb 

● Working of drive circuit-

■ What is a Arduino uno board ?

● Arduino uno is a programmable microcontroller IC which is based on ATmega328P microcontroller IC.

● C++ Programing language is used. 

》 FEATURES -

● It is an ATmega328P based Microcontroller

● The Operating Voltage of the Arduino is 5V

● The recommended input voltage ranges from 7V to 12V

●The i/p voltage (limit) is 6V to 20V

● Digital input and output pins-14

● Digital input & output pins (PWM)-6

● Analog i/p pins are 6

● DC Current for each I/O Pin is 20 mA

● DC Current used for 3.3V Pin is 50 mA

● Flash Memory -32 KB, and 0.5 KB       

memory is used by the boot loader

● SRAM is 2 KB

● EEPROM is 1 KB

■ Implementation of arduino based speed control of stepper motor

●In ULN2003 IC Pin 1 to 7 is the input in which 1 to 4 pin is used as a input and pin 10 to pin16 is the output pin in which 13 to 16 pin used as a output connected to stepper motor. 

●When the input is the logic high by arduino uno then the transistor 1 will be activated.

●So the current from the winding flowing through the collector of the transistor 1 and going out from the emitter and flowing to the base of the transistor 2 and goes out to the emitter and back to the ground. 

The winding is energized and motor rotates in steps. 

●Video of arduino based speed control of stepper motor