EXPT. NO. 1- CONVERTER FED DC SERIES MOTOR

Aim : To study the starting and running characteristics of converter fed DC series motor.

Apparatus :

5 Tachometer 01

Theory : Single phase controlled rectifier fed DC series motors are employed in traction. Controlled rectifiers are used to get variable dc voltage from an ac source of fixed voltage. As thyristors are capable of conducting current in only one dierctions, rectifiers are capable of providing current in only one direction. In series motor, the flux is a function of armature current. In unsaturated region of magnetization characteristic, flux can be assumed to be proportional to armature current. Series motors are suitable for applications requiring high starting torque and heavy torque overloads.

Procedure :

a) Switch ON the firing circuit and observe the trigger outputs.

b) Make sure that the firing pulses are proper before connecting to the power circuit.

c) Make the inter connections in the power circuit as given is the circuit diagram for different experiments using SCRs and diodes.

d) Connect motor Armature terminals to load points.

e) In the power circuit, Initially set the AC input to 230 volts from single phase isolation transformer.

f) Then connect the trigger output from firing circuit to corresponding SCR’s.

g) Switch ON the Power circuit MCB.

h) Switch ON the Trigger outputs switch and observe the output wave forms across load by varying the firing angle potentiometer.

i) Vary the firing angle from 180 degree to 0 degree and note down O/P voltage, current and speed of the motor using Tachometer.

j) After taking all the readings, set the firing angle 180 degree, Switch off the trigger outputs switch, switch off the power circuit MCB.

S. No. Name of Equipment Quantity1 1-Phase Converter Power Circuit (230V,5A) 012 1-Phase Converter Firing unit 013 Isolation Transformer (5A) 014 DC Series Motor(1500RPM,220V,3A,0.5HP) 01

NOTE :-

If you are not getting the output after all proper connections, interchange AC O/P terminals after switch OFF the MCB. This is just to synchronize the power circuit with firing circuit.

Cicuit Diagram :

Single phase Half controlled Converter fed DC Motor : +

Single phase Full controlled Converter fed DC Motor :

Observation table:

Single phase Half controlled Converter fed DC Motor :

Sl. No. Input Voltage

Firing angle

Output Voltage

Output Current

SpeedRPM

A

M

Isolation transformer

230V AC

MCB

T1 T2

DM

D3 D4

M

Isolation transformer

230V AC

MCB

T1 T2

DM

T3 T4

A

V

V

Vin Vo Io

Single phase Full controlled Converter fed DC Motor :

Sl. No. Input Voltage

Vin

Firing angle

Output Voltage

Vo

Output Current

Io

SpeedRPM

Result :