Sources of Farm Power in the Farm – Human, Animals, and Electric Motors

2 Classification of Agricultural Operations

• Tractive Work

• Stationary Work

4 Types of Tractive Work

1. Land Preparation

2. Cultivating

3. Harvesting

4. Transport

3 Types of Stationary Work

1. Threshing

2. Water Pumping

3. Milling

6 Common Sources of Power and Energy for Agro-Industrial Operation

1. Human Power

2. Animal Power

3. Electricity

4. Solar

5. Wind

6. Water/Hydropower

7. Biomass

8. Heat Engines

Still considered as the major source of power in the farm

Human power

6 Reasons why human power is still considered as the major source of power in the farm

Size of farm, Topography, Crops grown, High cost of equipment, High cost and non-availability of fuel, Availability of low-cost labor

The oldest source of power in the farm

Human Power

Considered as poor source of power

Human Power

A mature human being can continuously develop an output of ___ if he/she is in good physical condition, well-fed and working in a favorable environment.

0.10 hp

best suited to farm operations requiring judgement rather than just manual labor

Man

Considered as the major beast of burden in the Philippines

Carabao

Carabao can generate ___ hp walking continuously under favorable conditions

1 hp

Its work is confined mostly to pulling operations such as plowing, harrowing, cultivating and transport

Carabao

Population reduction of draft animal in the Philippines was due to?

1. Lifting of the carabao slaughter ban;

2. Hoof-and-mouth disease epidemic in 1975;

3. Naturally low birth rate of carabaos

Today, the population of carabao is maintained at the level of about ____ heads.

2.5 million

About ___ is used for draft work with the rest used for milk production

70-75%

The contribution of animal power in the farm is about ___.

0.16 hp/ha.

The animals were made to pull loads of ___ by using a wooden sledge as the loading device.

50 to 300 kg

The line of pull for carabao was measured from the horizontal plane and ranged from _____ degrees.

18-24

The line of pull for cattle was measured from the horizontal plane and ranged from _____ degrees.

24-30

The horizontal component of the pull, parallel to the line of motion.

Draft

Average speed of carabao

4.38 kph

Average speed of cattle

3.52 kph

With the increase in load, the speed decreased, and the animals could not pull the load of ___ and beyond.

300kg

About ___ of the weight of the carabao would be an optimum draft under normal conditions.

15%

7 Advantages of animal power

1. Low initial cost

2. Easy to maintain

3. Rarely bogs down in mud

4. Can work closer to the levees

5. Mobile in most terrain conditions

6. If female, is capable of reproduction

7. Source of milk, meat, leather, and fertilizer

4 Disadvantages of animal power

1. Low work output

2. Prone to disability by disease, poisoning, lost by rustling and death

3. Requires daily attention such as feeding and pasturing

4. Under poor management practices, causes unsanitary conditions

Range of animal performance efficiency of bovines

9 to 10%

Range of animal performance of horse family

10-12%

Generally, draft animal force is approximately __ of the body weight.

10%

Of all the draft animal, ___ has the highest output.

Horse

Horse can work within ___ hours.

8 to 10

Adult oxen can work within ___ hours.

5 to 8

Electro-mechanical devices used to convert electrical energy into mechanical energy

Electric motors

provide stationary power for various agricultural operations.

Electric motors

Energy conversion efficiency of electric motor

50-99%

Energy conversion efficiency of gasoline engine

25%

Energy conversion efficiency of diesel engine

40%

They are commonly used as prime movers for stationary and indoor equipment such as those used for processing of farm products and by-products

Electric motors

9 Advantages of Electric motors

1. low initial cost

2. available in fractional hp sizes (1/4, ½, ¾ Hp) and low integral hp sizes (1, 1 ½, 2, 2 ½, 3 Hp)

3. Compact

4. long life

5. easy to start and simple to operate

6. inexpensive to operate

7. quiet operation

8. no exhaust fumes

9. potential for automatic control

3 Disadvantages of Electric Motor

1. not adapted to mobile applications such as field machines;

2. used only in farms with existing electric lines

3. affected by power outages

Use direct-unidirectional current

Direct current motors

commonly used in special applications where high torque starting or smooth acceleration over a broad speed range is required.

Direct current motors

3 Main Components of direct current motors

1. Field pole

2. Armature (rotor)

3. Commutator

Where the interaction of two magnetic fields causes the rotation in a DC motor.

Field pole

The north and south poles that are stationary and an armature (rotor) that turns on bearings in the space between

Field pole

becomes an electromagnet when current goes through it.

Armature (rotor)

linked to a drive shaft in order to drive the load.

Armature (rotor)

it rotates in the magnetic field established by the poles, until the north and south poles of the magnets change location with respect to the armature.

Armature (rotor)

the current is reversed to switch the south and north poles of the armature. Thus, rotation is achieved

Armature (rotor)

It can only be found in DC motors

Commutator

Its purpose is to overturn the direction of the electric current in the armature.

Commutator

It also aids in the transmission of current between the armature and the power source.

Commutator

use an electrical current, which reverses its direction at regular intervals.

Alternating current motors

majority of electrical motors used in homes and on farms are alternating current motors

Alternating current motors

2 Majot parts of Alternating current motor

1. Stator

2. Rotor

difficult to control the speed; can be equipped with variable frequency drives

Alternating current motors

runs at constant speed; requires direct current (DC) for excitation; low starting torque.

Synchronous Motors

Its application low load requirement such as air compressors, frequency changes and motor generators. It is able to improve the power factor of a system, which is why they are often used in systems that use a lot of electricity

Synchronous Motors

more widely used with very large horsepower and relatively low speed.

Three-phase synchronous motors

the most popular motors in industry because of their ruggedness and lower maintenance requirements.

Induction motors

inexpensive, half or less of the cost of a DC motor, and also provide a high power to weight ratio, about twice that of a DC motor

AC induction motor

2 main electrical components of induction motor

1. Stator

2. Rotor

2 types of rotors

1. Squirrel-cage rotor

2. Wound rotor

consists of thick conducting bars, short-circuited at both ends by means of short-circuiting rings, embedded in parallel slots

Squirrel-cage rotor

It has a three-phase, double-layer, distributed winding. It is wound for as many poles as the stator. The three phases are wired internally, and the other ends are connected to slip-rings mounted on a shaft with brushes resting on them.

Wound rotor

Classification of electric motors based on electrical service required

1. Single-phase alternating current

2. Three-phase alternating current

Requires

Single-phase Alternating current

Requires >5hp of electrical service

Three-phase Alternating current

6 Motor Ratings and Selection

1. Torque requirement

2. Starting current requirement

3. Temperature rating

4. Duty rating

5. Enclosure

6. Service factor

The torque supplied by the motor is ___ than the required by the load

greater

If the load torque becomes ___than the motor torque, the motor will stall.

higher

During starting, a current of magnitude ___ larger than the full-load current is expected.

2 to 7 times

A _____designated by a letter on the motor nameplate, may be used to compute for the starting current.

motor code

____ are built with four insulation classes and are classified by the maximum temperature any spot in the motor can tolerate continuously.

motors

Both bearing and insulation life are ___ as the operating temperature of the motor increases

reduced

Normal maximum ambient temperature for motor operation is ____ for most motor ratings

40ºC (104ºF)

refers to how frequently the motor is started and for how long it will run each time it is started

Motor duty

the type of service in which the motor is operated for more than 60 minutes at a time.

Continuous duty

operated only for up to 30 minutes at a time with a rest or cooling period between operations

Intermittent duty

Use of ____ is a matter of cost. Heat dissipation is not as critical on an intermittent duty motor; therefore, some components can be constructed less expensively.

intermittent duty motors

Type of enclosure that allows for easy movement of air through the windings by providing slots in the end shields or frame where air can pass through.

Open-type enclosure

attached to the rotor shaft sucks the air in through the slots in the front-end shield and out of the rear end shield.

blower

This is desirable for motors operating in clean air or where water is kept from entering the motor.

Enclosure

Type of enclosure that does not allow entry of air to the windings.

Closed-type enclosure

constructed on the frame to increase the surface area for heat dissipation.

Fins

Type of enclosure that are not affected by dusty conditions and water splashes.

Closed-type enclosure

indicates the maximum load that can be successfully carried by the motor if it is to operate continuously and remain within a safe temperature range.

Service factor

Service factor of integral horsepower motor

1.15

Range of service factor of fractional horsepower motor for ¾ hp and 1/20 hp

1.25 to 1.4

The ___ on the nameplate is multiplied by the horsepower rating to give the maximum load that the motor can safely sustain.

service factor

carries a good deal of essential information about the motor, refer to it when you specify, buy, install, replace, operate and repair motors.

Motor nameplate

The information generally found on the nameplate

1. Name of manufacturer

2. Model name or number

3. Frame designation

4. Horsepower

5. Motor code

6. Cycle or hertz

7. Phase

8. RP

9. Voltage

10. Current

11. Duty

12. Ambient temperature

13. Service factor

14. Insulation class

15. Bearings

This name provides an indication of the quality of the product

Name of manufacturer

This accurately describes the product

Model name or number

designation for frame design for interchangeability between motors from different manufacturers.

Frame designation

Full-load horsepower rating.

Horsepower

Letter designating starting current requirement (F, G, H, J, K, or L).

Motor code

Frequency of the electrical source to be used (50/60 Hz).

Cycle or hertz

Number of phases of source (single-phase or three-phase).

Phase