DC Motors and Generators ~ TECHNICALJOB

UNIT OBJECTIVE

At the point when you have finished this unit, you will actually want to utilize the

DC Motor/Generator module to show and make sense of the activity of

dc engines and generators

DISCUSSION OF FUNDAMENTALS

Operating principle of dc motors

Working rule of dc engines

As expressed in Unit 1, engines turn due to the cooperation between two attractive

fields. This unit will talk about how these attractive fields are delivered in dc engines,

furthermore, how attractive fields incite voltage in dc generators.

The fundamental standard of a dc engine is the formation of a pivoting magnet inside the

versatile piece of the engine, the rotor. This is achieved by a gadget called the

commutator which is found on all dc machines. The commutator creates the

substituting flows essential for the production of the pivoting magnet from

dc power given by an outside source. Figure 2-1 outlines a regular dc engine

rotor with its fundamental parts. This figure shows that the electrical contact between the

sections of the commutator and the outer dc source is made through

brushes. Note that the rotor of a dc engine is likewise alluded to as the armature.

In Figure 2-2a, the brushes connect with fragments An and B of the

commutator and current streams in wire circle A-B. No current streams in the other wire

circle (C-D). This makes an electromagnet A-B with north and south poles as

displayed in Figure 2-2a.

Setting up the equipment

1. Install the equipment required in the EMS workstation

Assuming you are playing out the activity utilizing the EMS framework, guarantee that the brushes

of the DC Motor/Generator are acclimated to the nonpartisan point. To do as such, associate an

ac power source (terminals 4 and N of the Power Supply) to the armature of the

DC Motor/Generator (terminals 1 and 2) through CURRENT INPUT I1 of the information

securing module. Associate the shunt twisting of the DC Motor/Generator

(terminals 5 and 6) to VOLTAGE INPUT E1 of the information securing module. Begin

the Metering application and open arrangement setup document ACMOTOR1.DAI. Turn

the Power Supply on and set the voltage control handle with the goal that an air conditioner current

(shown by meter I line 1) equivalent to a large portion of the ostensible worth of the armature current

streams in the armature of the DC Motor/Generator. Change the brush change switch

on the DC Motor/Generator with the goal that the voltage across the shunt winding (demonstrated

by meter E line 1) is least. Turn the Power Supply off, leave the Metering

application, and disengage all leads and link.

Precisely couple the central player/dynamometer module to the

DC Motor/Generator utilizing a crankshaft belt.

2. On the Power Supply, ensure the principle power switch is set to the O (off)

position, and the voltage control handle is turned completely counterclockwise.

Guarantee the Power Supply is associated with a three-stage power source.

3. Guarantee that the information obtaining module is associated with a USB port of the

PC.

Associate the POWER INPUT of the information procurement module to the

24 V - AC result of the Power Supply.

an If you are utilizing the Prime Mover/Dynamometer, Model 8960-1, associate its LOW

POWER INPUT to the 24 V - AC result of the Power Supply

On the Power Supply, set the 24 V - AC power change to the I (on) position.

an If you are utilizing the Four-Quadrant Dynamometer/Power Supply, Model 8960-2,

turn it on by setting its POWER INPUT change to the I (on) position. Press and hold

the FUNCTION button 3 seconds to have uncorrected force values on the showcase

of the Four-Quadrant Dynamometer/Power Supply. The sign "NC" shows up

close to the capacity name on the showcase to demonstrate that the force values are

uncorrected.

4. Begin the Data Acquisition programming (LVDAC or LVDAM). Open arrangement

design document DCMOTOR1.DAI.

an If you are involving LVSIM-EMS in LVVL, you should utilize the IMPORT choice in the

Document menu to open the design record.

In the Metering window, select format 2. Ensure that the persistent

invigorate mode is chosen.

5 Set the Four-Quadrant Dynamometer/Power Supply or the Prime

Mover/Dynamometer to work as a brake, then, at that point, set the force control to

greatest (handle turned completely clockwise). To do this, allude to Exercise 1-1 or

Practice 1-2 if vital.

an If you are playing out the activity utilizing LVSIM®-EMS, you can focus in on the

Main player/Dynamometer module prior to setting the controls to see

extra front board markings connected with these controls.

Motor speed versus armature voltage

7-Turn the Power Supply on.

On the brake, set the force control to least (handle turned completely

counterclockwise).

On the DC Motor/Generator, set the FIELD RHEOSTAT with the goal that the field

current ܫ ௙indicated by meter I field in the Metering window is equivalent to the

esteem given in Table 2-1.

. In the Metering window, ensure that the force rectification capacity of the

Force meter is empowered. The Torque meter currently demonstrates the dc engine

yield force. Record the armature voltage, armature current, field current,

yield force, and speed in the Data Table. These boundaries are demonstrated

by meters E arm. (ܧ ,(஺I arm. (ܫ ,(஺I field (ܫ ,(௙Torque, and Speed,

individually.

On the Power Supply, set the voltage control handle to 10%, 20%, 30% and so on up

to 100 percent to expand the armature voltage ܧ ஺by steps. For each

voltage setting, hold on until the engine speed settles, and afterward record the

information in the Data Table.

Separately-Excited, Series, Shunt, and Compound DC Motors

At the point when you have finished this activity, you will actually want to show how the

field current influences the attributes of an independently invigorated dc engine utilizing the

DC Motor/Generator module. You can likewise show the fundamental

working attributes of series, shunt, and compound engines.

Separately-excited dc motor

energized dc engine

It is feasible to change the attributes of an independently energized dc engine by

changing the strength of the proper attractive field created by the stator

electromagnet. This can be completed by changing the current that streams in the

stator electromagnet. This current is typically alluded to as the field current (ܫ (௙

since it is utilized to deliver the decent attractive field in the dc engine. A rheostat

associated in series with the electromagnet winding can be utilized to differ the field

current.

Figure 2-15 shows how the speed versus armature voltage and force versus

armature current connections of an independently energized dc engine are impacted

at the point when the field current is diminished underneath its ostensible worth. Steady ଵ

becomes more noteworthy and steady ଶ decreases. This implies that the engine

can pivot at higher rates without surpassing the ostensible armature voltage.

In any case, the force which the engine can create, without surpassing the

ostensible armature current, is diminished.

SERIES MOTOR

Series engine

The series engine is an engine where the field electromagnet is a series winding

associated in series with the armature as displayed in Figure 2-16. The strength of

the field electromagnet, in this manner, fluctuates as the armature current shifts. As a

result, ଵ and ଶ differ when the armature current shifts. Figure 2-16 shows the

speed versus force normal for a series engine when the armature voltage

is fixed. This trademark shows that the speed diminishes non straightly as the

force increments, i.e., as the armature current increments. The series engine gives a solid beginning force and a wide scope of working

speeds when it is provided by a fixed-voltage dc source. Notwithstanding, the speed,

force, and armature current rely upon the mechanical burden applied to the

engine. Likewise, the series engine has non-direct working qualities as

proposed by the speed versus force relationship in Figure 2-16. Thus, it

is challenging to work a series engine at a steady speed when the mechanical

load changes. Moreover, the armature current should be restricted to forestall

harm to the engine when it is beginning (when power is applied to the engine).

At long last, a series engine should never run without mechanical burden in light of the fact that the

speed increments to an exceptionally high worth which can harm the (engine

runaway).

Today, series engines can work with fixed-voltage power sources, for instance,

vehicle turning over engines; or with variable-voltage power sources, for instance,

footing frameworks

SHUNT MOTOR

Shunt engine

The shunt engine is an engine wherein the field electromagnet is a shunt winding

associated in corresponding with the armature, both being associated with a similar dc

voltage source as displayed in Figure 2-17. For a decent armature voltage,

constants ଵ and ଶ are fixed, and the speed versus force trademark is very

like that got with an independently energized dc engine controlled by a fixedvoltage dc source, as displayed in Figure 2-17. As in an independently invigorated dc engine,

the attributes (ଵ and ଶ) of a shunt engine can be changed by differing the

field current with a rheostat. In any case, it is challenging to change the speed of a shunt

engine by changing the armature voltage, since this changes the field current,

also, subsequently, the engine attributes, in a way that goes against speed change.

The primary benefit of a shunt engine is the way that main a solitary fixed-voltage

dc source is expected to supply capacity to both the armature and the shunt

winding. Additionally, speed differs little as the mechanical burden shifts. Notwithstanding, a shunt

engine has a restricted speed range since speed won't be quickly changed by

differing the armature voltage. Moreover, the armature current should be restricted

to forestall harm to the engine when it is beginning (when power is applied to the

engine). At last, when the shunt winding opens incidentally, the field current ܫ௙

becomes zero, the engine speed expands quickly, and engine runaway happens as

proposed by the speed versus field current trademark

Compound motor