How to repair inverter part 1

Learn this simply way of repairing an inverter.

 

How to repair inverter

Inverter repairs  is not common and repairing a faulty inverter has not been an easy task for the local electronic repairers. This has made the few of us who does professional repairs to charge more especially when the inverter is a foreign made. I particularly do this to promote local inverter manufacturers as well as my products and discourage others from buying inferior foreign inverters which can even fail on same day. Lets start this first part of inverter repairs by knowing the types of inverters we currently have on market.

TYPES OF INVERTER

On the commercial market, the types of inverters seen are square wave two stages inverters, square wave single stage low frequency inverters, modified sine wave two stages inverters , modified sine wave single stage low frequency inverters, pure sine two stages inverters, pure sine single stage low frequency inverters.


TWO STAGES INVERTERS



Two stages inverters are inverters that first converts the input battery voltage to 300V - 310V DC using high frequency. This is achieved by switching ferrite transformers at high frequency. The square wave output of the ferrite transformer is then rectified using diode bridge rectifier and filtered using 400V electrolytic capacitors. This ends the first stage of the two stages inverter.
Before we go to the second stage, please know that the components in the second stage is powered by a separate 15- 25V winding on the ferrite transformer used for the 310V switching.
The second stage of two stages inverters works by converting the 310V DC to 220V AC pure sine or PWM or Square Wave using mosfet bridge or mosfet half bridge with an appropriate control drive circuit.


SINGLE STAGE (LOW FREQUENCY CONVERTERS)


This type of inverters consists of a driver stage (oscillator stage) and mosfet switches arranged in either a push pull ( for center tap transformer inverters ) or H-bridge ( for inverters without center tap transformers. This type has mosfets fixed on three different heat sinks.)

OSCILLATOR STAGES OF ALL CONVERTERS

Every inverter is made up of a control signal generation stage called the oscillator. The oscillator in lay mans term can be explained as an electronic signal that goes on and off at a set frequency. For inverters, the set frequency may be either 50 times in one second (50Hz) or 60 times in a second (60Hz)

Currently, inverters on market uses either a pulse width modulation (PWM) IC for their oscillation stage or a microcontroller with built in PWM.

COMMON INVERTER OSCILLIATOR ICS


commercial inverters and UPS are built around the following ICs.


SG3525

SG3524

TL494

CD40..

MICRO CONTROLLERS

Common Decision making ICs (OP AMPS) used in commercial inverters



LM324

LM358

LM339

LM471

LM258

ETC.
FUNCTIONS OF THE OP AMPS IN INVERTERS

Every good inverter has a number of operational amplifiers (OP AMPS) configured or designed to take simple decisions for the inverter. These decisions may include:


Battery Low

Battery Full

overload in some cases

high and low temperature

Fault.

In How to repair inverter part 2, I will tell you how these op amps can cause fault and how to remove or solve the faults in few minutes.
Now that you have idea of the compositions of an inverter, lets start our troubleshooting and repairs by reading INVERTER REPAIRS 2.