Inverter motors

Inverter
 device which supplies variable frequency of power supply on equipment
 motor revolution speed can be controlled and it leads to reduce energy
consumption

Basic structure of inverter device
 Inverter device consists of mainly two parts; converter and inverter
 Originally the meaning of “Inverter” is changing DC power source into AC
power source.
 In order to make supplied frequency variable, once the AC power source is
changed into DC at Converter part

 Function of Converter
 Converter part converts AC power supply into DC thanks to Diode
bridge circuit
 Diode: electrical component which allows current go through on one
way

 Function of Inverter
 By signal being input on each transistor, current will go through the
motor. This signal input format is different according to the motor (AC
inverter / DC inverter)

Transition of inverter technology

AC Inverter versus DC Inverter
 The inverter that drives an AC motor is called “AC inverter”
 the one which drives DC motor is called “DC inverter”

 Structure of AC Motor

 Principle how AC motor works?

 Advantage and disadvantage of AC motor
 ADVANTAGES
Simple structure
Easy to control
induction current is generated on the cage according to the
rotating magnetic field, so the rotor will be driven accordingly
without detecting rotor position.

 DISADVANTAGES
Less efficiency caused by
 induction current loss
 motor slip

 Structure of DC motor
 rotor is made of permanent magnet

 Principle how DC motor works?

 Advantage and disadvantage of DC motor
 ADVANTAGES
Less loss and better efficiency than AC motor because of
no motor slip
no induced current loss

 DISADVANTAGES
Needs enough knowledge to drive
Rotor position needs to be detected anytime to drive it and
stator coil should be energized accordingly to the rotor
position.

Evolution from AC Inverter to DC
Converter
 Demand for more efficient, less energy consumption
 In order to attain better efficiency, it is not enough only to apply (AC)
inverter technology so as to reduce the compressor speed, but also to
reduce energy consumption when In partial load conditions
 DC motor has been known as much more efficient motor than AC, and its
efficiency is roughly double compared to AC
 DC inverter is a good solution for reducing energy consumption.

DC PAM inverter
 DC Pulse Amplitude Modulation Inverter
 booster circuit is added on the converter part to raise up DC voltage.

DC PAM inverter
 DC Pulse Amplitude Modulation Inverter

DC PAM inverter
 Importance of PAM Control
 To apply more efficient dc motor
motor which have larger number of winding on one slot has better
efficiency because it can generate stronger magnetic field
Disadvantage: cannot accept bigger current because the diameter
of the wire should be thin
Solution: raising input voltage up, making the total input same
without increasing current, and become possible to drive the
compressor at higher torque

Vector control DC inverter
 cutting-edge technology of the inverter control in order to let the
compressor give the better performance by generating sinusoidal current
wave form

 Importance
 less compressor starting failure
detect the rotor position correctly, and it lead to improve
compressor starting
 Downsizing and high efficiency
High revolution operation on high efficiency (high turn motor)
compressor became possible thanks to the sinusoidal wave form
drive

 Importance
 to apply more efficient DC motor
detect the rotor position correctly, and it lead to improve
compressor starting
a motor which has a larger number of windings on one slot has
better efficiency because it can generate a stronger magnetic field
there is no non-energized period and it leads to reduce peak
current that can make a more efficient compressor DC motor
Disadvantage: cannot accept bigger because the diameter of the winding
wire

Types of Inverter
 Modified Sine Wave
 In a modified sine wave, the voltage rises and falls abruptly, the phase
angle also changes abruptly and it sits at 0 Volts for some time before
changing its polarity.
 A modified sine wave inverter actually has a waveform more like a
square wave, but with an extra step or so

Modified Sine Wave Inverter
 type of home inverter obtains power from a battery of 12 volts and must be
recharged using a generator or a solar panel
 held as the best inverters for homes as they are efficient enough to provide
power to the normal home requirement
 electric appliances that involve motor speed controls or timers are not to be
run using these types of home inverters

Sine Wave Inverter
 A sine wave is what you get from your local utility company and from a
generator
 the sine waves they produce are purer.
 employed for the power sensitive appliances like refrigerators, televisions, air
conditioners, washing machines
 The only drawback is that they are a bit expensive and cannot be afforded by the
common man

Advantages
 Sine Wave Inverter
 a complex design producing the AC wave power output similar to that
you would get from your house power point
 support all the complicated, sensitive or medical-electrical equipment
which will fail to run from the poor power output of a modified wave
inverter
 worth its cost if you want to support expensive and sensitive electrical
equipment
 high quality power output from the pure sine wave inverter will
maintain the unit’s power supply throughout, thus supporting these
appliances

Advantages
Sine Wave Inverter
 The output wave-form is a sine-wave with very low
harmonic distortion and clean power like utility supplied
electricity
 Inductive loads like microwaves and motors run faster,
quieter and cooler
 Reduces audible and electrical noise in fans, fluorescent
lights, audio amplifiers, TV, fax and answering machines
 Prevents crashes in computers, weird print outs and
glitches in monitors

Disadvantages
 Modified Sine-wave Inverter
 Some examples of devices that may not work properly with modified
sine wave and may also get damaged are given below:
Laser printers, photocopiers, magneto-optical hard drives
The built-in clocks in devices such as clock radios, alarm clocks, coffee makers,
bread-makers, VCR, microwave ovens etc may not keep time correctly
Output voltage control devices like dimmers, ceiling fan / motor speed control
may not work properly (dimming / speed control may not function)
Sewing machines with speed / microprocessor control

Transformer-less capacitive input powered devices like (i) Razors,
flashlights, night-lights, smoke detectors etc (ii) Re-chargers for
battery packs used in hand power tools.
Devices that use radio frequency signals carried by the AC
distribution wiring
Disadvantages

Some new furnaces with microprocessor control / Oil burner primary controls
High intensity discharge (HID) lamps like Metal Halide lamps. These may get
damaged. Please check with the manufacturer of these types of devices for
suitability
Some fluorescent lamps / light fixtures that have power factor correction
capacitors. The inverter may shut down indicating overload
Disadvantages

Disadvantages
 Will not function properly in any device that uses a control circuitry
that senses the phase (for voltage / speed control) or instantaneous
zero voltage crossing (for timing control)
 modified sine wave is a form of square wave, it is comprised of multiple
sine waves of odd harmonics (multiples) of the fundamental frequency
of the modified sine wave

Single-Phase, H-bridge Step-Waveform
Inverters
A H bridge is an electronic circuit that enables a voltage to be applied across a load in
either direction.
used in robotics and other applications to allow DC motors to run forwards and
backwards

Pulse-Width-Modulated Voltage-Source
Inverters
 Switches states many times during a single cycle of the resulting output voltage
 Disadvantage: requires faster components, high power high frequency
components

Three-phase Inverter
used for variable-frequency drive applications and for high power applications

Advantages of Inverter
 Modern drives can control starting currents
 maintain precise set speeds, quickly change speeds, control reversing and quickly
stop
 potential for energy savings, reduce energy input by 25% to 50% with the simple
addition of an inverter
 continuously adjust the speed to maintain a desired situation under varying system
conditions
 Multiple machines can be coordinated to have the right number of parts come
together in the right place, and at the right time
 Another great advantage is the potential for energy savings

disadvantages
 Early inverters caused significantly higher temperature rise in
the motor and mismatched could easily burn out the motor
 increased motor noise and bearing failure
 Burned Endturns
 “Typical inverter spike damage to motor windings. Usually in the
first turn near the lamination stack.”

Inverter motors

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