Download Cooling Systems

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Nanogenerator wikipedia , lookup

Giant magnetoresistance wikipedia , lookup

TRIAC wikipedia , lookup

Switched-mode power supply wikipedia , lookup

Schmitt trigger wikipedia , lookup

Operational amplifier wikipedia , lookup

Lumped element model wikipedia , lookup

Negative resistance wikipedia , lookup

CMOS wikipedia , lookup

Power MOSFET wikipedia , lookup

Valve RF amplifier wikipedia , lookup

Regenerative circuit wikipedia , lookup

Index of electronics articles wikipedia , lookup

Opto-isolator wikipedia , lookup

Surge protector wikipedia , lookup

Current source wikipedia , lookup

Current mirror wikipedia , lookup

Resistive opto-isolator wikipedia , lookup

Rectiverter wikipedia , lookup

Flexible electronics wikipedia , lookup

Integrated circuit wikipedia , lookup

Multimeter wikipedia , lookup

Network analysis (electrical circuits) wikipedia , lookup

RLC circuit wikipedia , lookup

Ohm's law wikipedia , lookup

Transcript
HVAC System Controls

Electrical fundamentals
 What
is electricity?
 How is it measured?
 Uses
 Complete circuits
 Malfunctioning circuits
 Ohm’s Law
 Series and parallel circuits

Testing equipment
1
Electrical Fundamentals

What is electricity?

How is it measured?

What does electricity do on AC
Units?
2
What is electricity?

Electricity is defined as the flow of electrons
3
What is electricity

How can we get electrons to flow?
1. Source
2. Path
4
What is electricity?

Source: something that has an imbalance of
electrons and protons

Protons are positively charged

Electrons are negatively charged

Since opposites attract, if we create an imbalance
of electrons and protons we have electrical
potential

Electrical potential is electrical pressure and it is
measured in volts
5
What is electricity?

6
Path: a conductor that connects the protons with the
electrons

A conductor is anything that has less than 4 electrons held loosely
in their atom’s outer orbit

This allows the electrons to move freely from one atom to another

An insulator holds its electrons in a tighter orbit and does not allow
movement easily

Once a path is established, electrons will move because of the
attraction caused by the imbalance in the source
What is electricity?

How do we know electrons are moving?

Can we hear, see or feel electrons moving?

We can only see the effects of electrons moving

Electrons if left unrestricted, will move so fast that
extreme heat is created from the friction
generated by their movement
7
What is electricity?

For safe movement, electrons must be restricted
in their movement

We can use the restrictors to do work for us on an
automobile
8
What is electricity?

Electricity: flow of electrons

What is required for electrons to flow?


A basic circuit
What is a basic circuit?

Source

Path

Restriction or load
9
How is it measured?

10
Volts: electrical pressure or potential

Volts do not move through circuits

Voltage is simply the strength of the imbalance between protons
and electrons and force the electrons to move through a
conductor

Voltage is measured with a voltmeter that measures the
imbalance between the positive side and negative side of a
circuit

Voltmeters must be wired in parallel
How is it measured?

Amperes: the measurement of the amount of
electrons flowing through the circuit

Amps are the measurement of current in an
electrical circuit

Amps are measured with an ammeter

For an ammeter to measure current in a circuit, the
current in the circuit must flow through the ammeter

Ammeters must be hooked up to a circuit in series
11
How is it measured?

Ohms: a measurement of electrons resistance to
flow through a circuit

Resistance must be present in a circuit to control
the flow of electrons

Resistance in a circuit can be measured with an
ohmmeter

An ohmmeter is self-powered and requires the
circuit to be open
12
How is it measured?
What unit of electricity is doing work?
13
Sources:
14

Electrochemistry: different metals placed in a chemical
solution causes a difference in electrical potential or voltage
between the two types of metal

Electromagnetism: when a conductor is moved through a
magnetic field, an electrical current is produced
Sources:
15

Piezoelectricity: when pressure is applied to certain types of
crystals, they develop a potential difference or voltage

Photoelectricity: certain types of metal can produce a flow of
electrons from light exposure
Uses for electricity on the
automobile:

Heat: windshield/seat heaters, etc.

Electrical resistance creates heat

Illumination

Magnetic fields:

rotary and linear motion; electricity generation; voltage
transformers

Chemical reactions

Electronics:

Logic; computers- modules; sensors; etc.
16
Complete circuit:

Power source

Protection

Insulated path

Load or resistance

Return path
17
Malfunctioning circuits:

Open circuit: lacks continuity or is incomplete



18
No current will flow
Shorted circuit: a portion of circuit is “short-cut”

Short to voltage

Short to ground

Current may or may not flow

May or may not blow circuit protection

Circuit control can be lost
High resistance

Causes a decrease in current
Open circuits
Causes:
19
Shorted Circuits
Short to voltage:
20
Short to
ground:
Shorts to ground may
not necessary blow fuse
Ohm’s law:
21

Establishes that pressure, resistance and amount of current
flowing through any circuit are all related

If two values are known, the third value can be calculated

It takes 1 volt to push 1 amp through 1 ohm of resistance
Ohm’s law:
22
Series circuits

A circuit that has more than one load and all
current flows through all the loads in the circuit

Series circuits used in an automobile:

Blower circuit where variable fan speeds are
required

Seat heaters using a variable resistor to control
temperature
23
24
Example of a series circuit for a blower motor
Series circuits

Total of all voltage drops will equal the source
voltage voltage drop

Voltage drop is proportional to resistance

The higher the resistance, the greater the voltage
drop

As resistance increases, current flow decreases
 Circuit
resistance is the sum of all loads
in the circuit
 Amperage
is the same at any point in
a series circuit
 voltage
drop AC Delco
25
Parallel circuits




A complete circuit with more than
one path for current to flow
Current flowing into each branch or
leg varies according to the amount of
resistance in that branch of the circuit
The total resistance of a parallel circuit
is always less than that of the smallest
resistance of any branch of the entire
circuit
The voltage is the same for each
branch of the parallel circuit
26
Parallel circuits




Most of the current flow in a parallel
circuit will occur in the branch with the
least resistance
As long as other branches of the circuit
are complete, current will flow through
them in accordance with Ohm’s law
The only place where electricity can take
the path of least resistance is in a series
circuit
Most lighting circuits on automobiles are
parallel circuits
27
Series-parallel circuits
Includes both parallel loads and loads
that are electrically connected in series
 Added resistance in series portion of
circuit, will decrease current flow through
parallel branches evenly
 Example of series-parallel circuit used in
automotive applications: dash board
illumination with a dimmer switch


As resistance increases with variable resistor in
dimmer switch: current flow is decreased through
dash lights
28
Testing Equipment



Always test your test equipment
before attempting to diagnose
electrical problems
Standard test lights have limited use
on late model vehicles
Test lights can draw enough current to
Damage electronic components
 Deploy air bags



Test lights cannot differentiate positive
and negative sides of a circuit
Test lights cannot measure resistance
29
Test lights

Self powered test lights: battery operated and
light up when connected to both sides of a circuit

LED test lights should be used in place of standard
test lights on computer controlled vehicles

LED’s draw very small amounts of current and
cannot damage electronic components
30
Digital multimeters
31

High impedance: high internal resistance that limits current
output

Can measure amps, volts and resistance

Automotive requirements for a DMM:

Diode checking

Frequency

Temperature

Duty cycle

RPM

Dwell
DMM’s/DVOM’s

32
Voltmeter: measures difference in voltage between leads
 Must
be hooked up in parallel
 Internal
resistance keeps meter from affecting
circuit being tested

Ammeter: measures amount of current flowing through circuit
 Most
 Must
meters cannot measure more than 10 amps
be hooked up in series or installed inside of
the circuit to measure amount of current flowing
DMM’s/DVOM’s


Ohmmeters:

Requires open circuit

Ohmmeter is self powered and may be
damaged if connected to a live circuit

Zero ohms means no resistance in circuit or
continuity
Meter use:

Select proper unit for what is being measured

Place leads in proper input sockets

Make measurement

Interpret reading
33
34
FLUKE 87
AC Switches
DVOM’s

Use of DVOM’s:

Select proper unit for what is being measured

Place leads in proper input sockets

Make measurement

Interpret reading
35
DVOM’s

“OL”:

Displayed on most meters

What it means:

Open leads


Infinite resistance
Over limit

Over maximum meter can read
36