dee-m.c-1 teasting of motor

7/31/2019 Dee-m.c-1 Teasting of Motor

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Parul Institute of Engineering

& Technology

Subject Code :330903

Name Of Subject : Machine -1

Name of Unit :D.C. MOTOR

Topic :Testing of d.c. motor


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Name of Faculty :Harshad

Mayavanshi

Name of Students:

(i) Parmar Kinjal(116380309009)(ii) Thite Vishruta

(116380309020)


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In this presentation, 2 most commonlyUsed methods are described briefly.

These two methods are:1) Direct Method &2) Indirect Method


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This method is suitable for small

d.c. machines.

In this method the d.c. machine is

subjected to rated load and theentire power output is wasted.

For a d.c. generator, the outputpower is wasted in resistor.


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D.C. MOTOR

Brake Test Swinburns Test


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BRAKE TEST


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Figure shows the arrangement for

this load test. It consists of a brakedrum keyed to the shaft of the

motor.

The brake drum is filled with water

to cool it. It is made of cast iron oraluminium.


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A belt is wrapped around the

drumad each end of the belt is

attached to a spring balance.

The spring balances are

suspended from a frame which isfixed rigidly.

Hand wheels are provided on thetop of the frame.


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The net torque in Kg-m is

calculated using the expression.


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ADVANTAGES

1) The test is simple.

2) Machine is actually loaded, so

true efficiency is obtained

3) As the machine is loaded, the

actual working condition is

produced, So the conditions likearmature reaction, heating,

commutation etc. are produced

when the machine will be used.


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DISADVANTAGES

1) Test is expensive as the outputpower is wasted.

2) Large amount of heat isproduced in machine of high

rating so there is difficulty of

cooling it. Due to these tworeasons, the test is limited for the

machine of the small rating.


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SWINBURNS TEST


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Losses are measured separately in

this method, and efficiency at any

desired load is predetermined.

The iron and friction lossescan be determined by

measuring the input to the

machine at no-load.


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The machine is run as a motor at

normal voltage and speed.

The copper losses are calculated

from measured values of the

various resistances. This method

is only applicable to levelcompounded and shunt motors.


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No load input current = ILoA

Supply voltage = V volt

So, the no load input power = V*ILo

No load armature current Iao = (ILo

Ish)

No load armature copper loss = Iao^2

Ra


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Input power = Output power + Total

lossLosses = No load armature copper

loss + Constant Losses Wc

V ILo = Iao^2 Ra + Wc

So, constant losses Wc = V ILo

Iao^2Ra


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ADVANTAGES

1) This test is economical as the

machine is run only at no load sopower equal to the losses is drawn

from the mains.

2) Efficiency of the machine can be

found either as motor or generator.

3) Machine is not loaded so no

arrangement is to be done for

loading of the machine.


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DISADVANTAGES

1)It is assumed that the iron losses of

the machine remain constant but in

practice when the machine is

loaded, there is change in flux dueto the armature reaction so the iron

losses change.

2) This test is used for the machine

whose speed remains almost

constant.


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3) Machine is tested at the no load

so it does not give any idea aboutcommutation, armature reaction,

heating etc. when the machine will

be actually loaded.


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Sub: M/c- 1

Topic: Testing of motor


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dee-m.c-1 teasting of motor

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