Electric Fence Energizer

8/12/2019 Electric Fence Energizer

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FenceFenceEnergizers

Tom Cadwallader and Dennis Cosgrove

University of Wisconsin-Extension

encing Systems for Rotational Grazing



ELECTRIC FENCING BASICS

"UNDERSTANDING THE BASICS OF ELECTRIC

FENCE ENERGIZERS"

With the increased use of electricfencing for containing animals andcontrolling grazing, many producershave found themselves trying tocomprehend electrical terms andconcepts.

The goal of this publication is tointroduce the novice fence builder tosome of the concepts and terms whichare used in perhaps the most important

part of any electric fence system, theenergizer

A BRIEF HISTORY OFENERGIZER DEVELOPMENT

Since the early days of electric fencing,the most commonly used energizershave converted electrical energy fromeither a standard 110 volt AC current, ora 9 volt DC dry cell battery into a highervoltage, DC, pulsing charge and sent it

into a light gauge electric fence wire.Many people who grew up with, andstill use these energizers, or fencecontrollers', can remember walking intothe barn and hearing the steady click,click, click as the controller slowly turnedon and off. They can also rememberchasing stock back into the barnbecause a branch, twig or clump ofgrass was laying across the fenceshorting it out. Attempts at increasing

the amount of electricity flowing out ofthese controllers became a great sourceof barn and grass fires because the longperiod of time that the current wasallowed to flow through the wirecaused both the wire and whatever ittouched to heat up.

The development and promotion ofnew types of energizer systemsprogressed slowly until the early 1960'swhen researchers in New Zealanddemonstrated technology which putlarge amounts of electrical power (highamperage and high voltage) through afencing system, in an extremely shortperiod of time (milliseconds), effectivelyflooding any short circuits that wouldhave made a conventional energizer

ineffective

The next step in the development ofwhat are now referred to as the “NewZealand” style energizers was thedevelopment of the electronics thatcould reliably supply the high voltage,high amperage and short durationsurge of power. The initial energizersthat were developed used a system verysimilar to a car's distributor, using amechanical switch and coil. These

quickly evolved into the next generationof energizers which utilize solid stateelectronics enabling them to deliverlarge amounts of energy with very littleresistance (impedance) in very shortperiods of time, usually around 0.0003seconds.

ELECTRICAL TERMINOLOGYUSED IN EVALUATINGENERGIZERS

Since electricity is not something thatcan be seen, it is difficult for manypeople to understand how it works, Thefollowing terms are often used toevaluate and compare energizer units.

1. Volts: Volts are a unit of measurementused to describe an amount of electrical

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potential, or "pressure". The higher thevoltage, the higher the pressure. In anelectric fence system, a high voltage isimportant for making sure that anelectrical charge can find its waythrough the hair on the animals it isintended on either keeping in or out.The more or thicker the hair, the greaterthe voltage required. For most animals,the optimal voltage range is generallyconsidered to be between 2000 and6000 volts. Voltages greater than thisare not normally necessary orrecommended and there are manyanimal species that are adequatelycontrolled with less.

2. Amps: Amps are a measure of the"amount" of electricity that flowsthrough the circuit (remember,electricity will not flow unless a circuit isbeing completed). It is amperage, notvoltage that causes the greatest amountof numbing pain when anythingreceives a shock. It is high amperagethat melts wires in houses and barnswhen more electricity is being carriedthan they are intended to handle. Thereason that circuit breakers and fuses

are put in electrical systems is to preventan excessive flow of energy from beingpulled through the circuit and heatingup whatever it runs through.

3. Watts: Watts are a measure of theelectrical rate of doing work. It is a unitof electrical power, which is very similarto horsepower and is calculated by theequation:

amps x volts = watts

The term watt is not used much indiscussions about energizers, but thedefinition of a watt is very important inunderstanding the next unit of measurethat is often used when comparingenergizers, the joule.

4. Joules: A joule is a unit of electricalenergy equaling the amount of energyrequired to produce one watt for onesecond. The equation is:

watts x seconds joules

As can be seen by these equations, thehigher the volts and amps that anenergizer can deliver, the higher thewatts. And the higher the wattsdelivered in the same pulse time, thehigher the joules. These equations areimportant to understand whencomparing energizers.

For Example:

- Unit A is listed as a 4.5 Joule energizerwhich can maintain 5000 volts underlow weed pressure. If Unit A's pulsetime, the time the fence is on, is 0.0003seconds than we can make thefollowing calculations by reversing theabove equations to see how muchelectricity the energizer is delivering:

4.5 joules/0.0003 sec. = 15000 watts15000 watts/5000 volts = 3 amps

- Unit B also claims to be a 4.5 jouleenergizer that can maintain 5000 volts,but was rated using a 0.0006 secondpulse time. Using these numbers in ourcalculation we find that:

4.5 joules/0.0006 sec. = 7500 watts7500 watts/5000 volts = 1.5 amps

Unit B is actually delivering half the

amount of electricity of Unit A. If wecompare them equally then Unit Bwould actually only be a 2.25 jouleenergizer.

There are currently no standards ineffect to assure consumers that themanufacturers and distributors ofelectric fence energizers are fairly and

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equally comparing the electricalattributes of their products to theircompetitors.

5. Low Impedance vs. High Impedance: As was mentioned previously, a highamperage electrical charge is whatcauses the greatest amount of damagewhen it flows through anything thatcompletes a circuit. In the olderconventional electric fence controllers,the pulse rate was very long, sometimesnearly half a second. If the flow ofelectricity is not controlled in these styleof energizers, they are not only apotential source of barn and grass fires,they can also be lethal to any animal

that would become caught in the wire.This is especially true if the wire is barbwire.

No fencing system containing barb wireshould ever be electrified. An owner ofsuch a fence would be considered liableif any animal or person were to becaught up in such a fence.

In order to reduce the chances of injuryor property damage, the manufacturers

of long pulse rate energizers put inresistors which restrict the flow ofcurrent out of the energizers, thus theterm "high impedance". These highimpedance energizers keep the amountof amperage down to a safe level butalso make them more prone to shortingout.

Low impedance energizers, don't wantto restrict the volume of electricity to theextent the older style energizers do.

They depend on the extremely highenergy discharge and short pulse rate tokeep an electric fence from being easilyshorted out. It is the millisecond pulserate that provides the safety factor in"low impedance" energizers.

6. Miles of fence: The standard of "Miles

of Fence" in describing the power of afence controller has been in use formany years. Although many companiesstill use this standard in evaluating theirenergizers, a unit which is rated as a fiftymile unit only means that it caneffectively power 50 miles of a weedfree, properly insulated, single strand of14 to 18 gauge wire that is 30 to 36inches off the ground. It does not takeinto consideration the weed loading orthe electromagnetic resistance thatoccurs in multiple wire fences. A 50 mileenergizer will not necessarily power 10miles of five wire high tensile fence. Although an energizer rated in "Miles ofFence" may be as good as a unit rated in

joules, it is difficult to make a faircomparison using this method of rating.

CHOOSING THE RIGHTENERGIZER FOR THE JOB

Choosing the "Right" energizer for the job is not an easy process. The power ofthe unit required for a fencing job willvary greatly depending on many factors,such as, the area to be fenced, thenumber of wires, the animal being

controlled, the use of higher resistancetemporary fencing and the expectedweed pressure.

As is the case with any farm equipmentwhich is purchased today, especially anelectrical device such as an energizerthat is containing and controllinglivestock, one of the most importantfactors in deciding on what kind ormake of energizer to buy is the dealersknowledge about what they are selling.

A responsible energizer dealer shouldset a novice fence builder up with theright energizer for the job and supply awritten guarantee that what they areselling will do what they say it will do.

Since the value of an electric fence isbased on its ability to deliver an

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adequate electrical charge to keepanimals away, purchasing an energizerthat is ill equipped for the job you areasking it to do makes a fence useless. Onthe other hand, purchasing a highpowered energizer to do a small job canbe a waste of money.

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Electric Fence Energizer