Types of inveter protection

Inverters must have various protections so that they can withstand the tests of time. At times, the inverters you design or build are not used by only you. Therefore its advisable to include some basic decision making functions for the inverter to behave at every point as though you are making those decision at those points in time.

Below are some basic inverter protections which can be achieve by using op amps configured as comparators. If you are into programing, you can also include them in your programs, else its advisable to use op amps. 

 INVERTER PROTECTIONS

• Overload warning alarm with indicator
  

• Overload shutdown

• Low battery alarm

• Low battery shutdown

• Over temperature protection with indicator

• Over battery protection

• Float charging system

• Temperature based fan control

INVERTER PROTECTIONS FUNCTIONS EXPLAINATION

•    Overload warning alarm with indicator: This function monitors the amount of load powered by the inverter.  When the total load connected to the inverter reaches 90% of the rated inverter system, the system alarm triggers with an indicator on. This prompts the user that He or She is about to overload the system.

• Overload shutdown: This function takes care of overloads and short circuit instances. When overload or short circuit occurs, this function turns off the inverter output to protect the inverter from damage.

• Low battery alarm and shutdown: This function takes care of battery protection. It is always good to ensure that, the battery of an inverter is not deeply drain to prolong the battery life. During inverter usage, this function monitors the battery level and triggers the system alarm when the battery level reaches a set level. After the alarm, the inverter turns off to protect the battery from over draining.

•  Over temperature protection with indicator: Every electronic system as well as inverters produces some amount of heat as a result energy conversion and power loss. But this heat should always be in an acceptable level to ensure high efficiency and avoidance of failure.

    The over temperature protection system monitors the system temperature and turn system function (charging or working as inverter) off when system temperature is above acceptable level which is a sign of possible problem.

• Over battery protection: This function is included to ensure that, if a customer buys the inverter and uses the wrong number of batteries (uses 24V instead of 12V), the system will never turn on until the correct battery system is used.

• Float charging system: When this charging technique is employed in designing, it ensures that the batteries are always charged without ever overcharging them.

• Temperature based fan control: The system fan should be designed to turn on only when the system begins to gain heat and turn off after extracting the heat. This function ensures that the inverter system is always silent.

fan control circuit

Automatic temperature controlled fan using NTC.
Sometimes, the systems that removes the heat can be disturbing with its noise. I want to show you a simple circuit that will remove heat from your electronic gadgets and systems that produces heat.

The advantage of this circuit is that, the fan only turns on when there is heat in the system and turns off after removing that heat.

Automatic  fan control circuit

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Simple automatic change over circuit

Simple automatic change over circuit for homes and work places.

Change overs are required whenever you are handling two or more power from different sources. In homes where inverters or generators are stand by power sources, it is advisable to use a change over system so that when your stand by power is in use, power will not flow into your national power supply.

Also, when change overs are not installed, power will run into your stand by source and destroy it. If its an inverter, all the output mosfets will blow up and even catch fire. Generators may also explode when that happens.

Change overs can be manual or automatic. With manual change overs, u have to wake up from your sleep to change over when your nation grid goes off or when your national grid is restored. Automatic change overs on the other hand does every switching automatically and even connect your inverter for charging.

The circuit is an automatic change over circuit with delay of 20 to 50 seconds, power restored notification alarm and charging port for those who will be using it for inverters.

The circuit is based on 555 timer IC, 220V Contactor, 12V relay, a buzzer, a transformer and few resistors and capacitors.

AUTOMATIC CHANGE OVER CIRCUIT FOR INVERTERS AND GENERATORS

HOW TO DOUBLE TRANSFORMER VOLTAGE

A circuit to double or step up the output of a small transformer so that it can power high voltage circuits. High voltages are at times needed but its a problem when we have to spend huge sums of money before we accomplish it.

Am going to show you a high current circuit which can double or even triple the output of any transformer connected to it. The circuit can be used as car battery chargers, inverter battery chargers and as a regular power supply. 

TRANSFORMER BOOST CIRCUIT FOR POWER SUPPLY AND CHARGERS

 

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AUTOMATIC SWICH CIRCUIT

Switch circuit which saves energy consumption by automatically turning off appliances connected to it either at day or at night. This switch circuit can be employed to reduce the energy consumption of fridges, air conditioners, lights, and many more appliances that you want to control their turn on time.

The circuit is based on light dependent resistor (LDR) popularly known as photo cell. The LDR is a type of resistor which reduces its resistance when light falls on it. The resistance value is directly proportional to the amount of light that falls on it. The more the light, the less the resistance of the LDR and the less the light, the high the resistance.

In this circuit, the LDR is our sensor which controls the relay U1 and also your connected load..

AUTOMATIC SWITCH CIRCUIT

BATTERY STEP DOWN CIRCUIT 12V, 24V, 36V, 48V, 96,120 - 300V

We are going to step down high DC voltage to low DC voltage using simple approach. This circuit can convert 18V - 300V DC to 12V, 24V, 36V, 48V and any stepped down voltage that you want.
The circuit can be used in inverter systems to step down the system voltage to a level that is acceptable for running the control board. The circuit can also find its use in offline converters and power adopters.

STEP DOWN 12V, 24V, 36V, 48V,96,120 - 300V CIRCUIT 

The Circuit is based on TOP244. TOP Switch-GX uses the same proven topology as TOP Switch, cost effectively integrating the high voltage power MOSFET, PWM control, fault protection and other control circuitry onto a single CMOS chip. The IC  is integrated with many functions to  reduce system cost and improve design flexibility, performance and energy efficiency. Click here to download the datasheet of the IC TOP244.

DC to DC converter Circuit Diagram

CIRCUIT EXPLANATION

 The circuit is a simple 2A to 5A switching circuit that steps down the input voltage to a desired output level. As said above, the circuit is based on TOP244 though other TOP ICs may work, this is what works best for our input range.TOP244 works with a minimum input voltage of 18V DC and a maximum input voltage of 400V. The IC has many built in function which most of it are currently disable so that the IC will be easy to use by us for our needs.

The only function that is still enable is overload protection which will prevent the IC from failing when there is a short circuit or overload.You can download the datasheet to read more about the other protections and how to enable them.

The circuit works when the TOP IC switches the ferrite transformer at a higher frequency about 132kHz.

This action produces square waves of 132kHz. at the secondary side of the ferrite transformer which is then rectified using D24. D24 can be any fast switching diode. the rectified DC is then filtered using C5 2200uf capacitor or better.

The output regulation of the circuit is achieved by using TL431 and optocoupler PC817 to provide feedback to the control pin 1 of the main IC. The feedback system ensures that the output is always stable. 

As shown in the circuit, the circuit provides 13.2V output from any given input. To change the output voltage, replace R1 and R3 with a single 10K variable resistor. When that is done, you can now adjust the output to any voltage you desire.

The LM7805 provides an alternate 5V for those who will want an addition 5V from the output. It can be ignore if you don't need a 5V supply.

Please note that all diodes used are fast switching diodes.

How To Wind ferrite Transformer for step down converter

Though any core can be used for this circuit some smaller cores will not give u better current.

 When winding the transformer, wind the secondary and the auxiliary with the same number of turns. 

Example:

When designing a 24V to 12V, primary turns can be 12turns whiles secondary and auxiliary can be 7 to 9 turns each.

You can also google on how to wind a ferrite transformer to learn more.