Getting Pure Sine Waves from Electronic Inverters

On February 2, 2018, in Other, by Lambert

Digital signal processors (DSPs) are being used in switching power supplies able to synthesize pure sine waves for use in high-reliability (hi-rel) military applications.


Ruggedized digital inverters were installed in the M1068, a Command Communications variant of the U.S. Army’s M113 family of armored personnel carriers. The original M113 Armored Personnel Carrier was first fielded in Vietnam. To date, an estimated 80,000 M113s, including a long list of variants, have been produced and used by over 50 countries worldwide, making it one of the most widely used armored fighting vehicles of all time.


During this time, the M113 has been continuously updated to meet the demands of the modern battlefield. Since then, the M113 family of vehicles are being upgraded, reconfigured and introduced as entirely new systems, including the M1068.


The M1068 variant is used as a tactical operations center capable of long range communications and includes 4.2-kW auxiliary power unit (APU) mounted on the right front of the vehicle to provide 24-V power.


As part of this project, BAE Systems required two hi-rel, ruggedized 2.5-W pure sine wave inverters per vehicle to convert 24 Vdc power generated by the vehicle-mounted APU into usable multi-kilowatt levels of ac for powering communications devices, lighting, computers and other electronic devices.


Although more expensive, pure sine wave inverters provide cleaner utility-grade power than quasi-sine-wave models. Pure sine wave inverters are helpful when operating sensitive electronic devices, including communications equipment, that require high-quality waveform with little harmonic distortion.


In addition, pure sine wave models have a high surge capacity, which means they are able to exceed their rated wattage for a limited time. This lets vehicle motors start easily, though they can draw many times their rated power during start up.


Bob Seidenberg, former Senior Quality Assurance Manager with BAE Systems, explained that the 2.5-kW inverters also had to meet shock and vibration requirements that could only be met by hi-rel inverters.


“The shock requirement for the inverters installed on the M1068 was close to 30 gs, in three directions (vertical, horizontal and transverse) and the vibration spectrum was also demanding,” he said.


The pure sine wave supplies come from Magnetic Design Labs in Santa Ana, Calif. According to Kamran Kazem, MDL VP and chief technology officer, despite the 30-g requirement for the M1068, the military specified that the inverters had to withstand 100 gs. This was well beyond the amount of shock the vehicle would ever realistically experience, based on military tests conducted in the roughest terrain that maxed out at 15 gs.


Kazem added that hi-rel electronic systems and components are no longer the exclusive domain of aerospace and defense. Today, medical, transportation, communications, infrastructure and industrial all have applications where the price of failure is high.


“These power converters might not have to withstand the same extreme conditions as the military, but vibration, shock, humidity and other inherent environmental problems are still factors, so the need for hi-rel and rugged power converters certainly applies to those markets as well.”


DSP is also a key element in a new generation of modular, stackable inverter options designed to provide a range of 1 to 20 kW of dc-ac power through a single, customizable unit. This type of system, available from custom power converter designers like MDL, consists of rack-mounted inverter modules that can stack in a parallel configuration, letting the user add as many inverters as needed to meet the power requirements.


Each unit connects to a communications controller that is responsible for synchronization, load sharing and any external communications. The individual inverters are hot swappable, enabling the addition or replacement of modules on the fly.


“This type of modular design provides project managers with a system that fits their power requirements without having to develop a new unit just for their specific project,” Kazem said. “This eliminates the need for many application-specific designs, and could also enable faster delivery of the power converter at a much more economical cost.”


Article Source: Power Electronic Tips


How to Select the Right Power Inverter for You

On July 18, 2016, in Other, by Lambert



A power inverter is an electronic device that converts electricity from one form to another. Power inverters have become more popular recently as the technology has become more efficient and much more affordable.


The most popular use for a power inverter is converting battery electricity into mains electricity. For example converting your car batteries’ 12 volts DC into mains electricity 240 Volt AC (Australia) or 110 Volt AC (USA).


Power inverters enable mains operated electrical equipment to be used even where there is no mains outlet, like in your car, caravan or even on your boat!


Power inverters bring creature comforts from home when you go camping or caravanning allowing you to use your TV, fridge or electric shaver in fact most of the normal mains powered conveniences from the home.

You can charge your laptop in the car even if it doesn’t happen to have a 12 volt adapter. In fact a power inverter can be a very handy gadget just to have in your car for those times you need to use a mains powered appliance while you’re away from a power socket.




Apart from looking for a good quality well priced product there are a couple of important elements to consider when selecting your power inverter:




Power inverters come in a range of power capacities so selecting the right one for you is very important. Your power inverter needs to be able to provide sufficient power for the equipment you want to use it with.


Here is a brief check list:


  • Check the power consumption for the device you want to power
  • Allow an additional 20% free board
  • Add the power for all the devices you want to run at the same time


Note also that devices with induction electric motors like an power saw may require 3 to 7 times the operating power when they start.


Using an under-powered power inverter may damage it or the appliance you are trying to use, so be sure to check the specific wattage requirements and operating instructions for appliances / tools to be used.




Normal mains power is known as Alternating Current (AC) and is a sine wave shape like the black line in the drawing below


Pure sine wave (black) versus modified sine wave (red)


A typical power inverter produces a ‘modified sine wave output’ like the red line in the drawing above. While this works for most appliances, light dimmers, variable speed drills, sewing machine speed controls, some laser printers etc. will not operate correctly with a modified sine wave power inverter.


Pure sine wave power inverters are especially designed to provide a more accurate sine wave output and so can be used with these appliances, but unfortunately they are more expensive.


Check with your with appliance manufacturer or its specifications to confirm if you can use a conventional power inverter or will need a pure sine wave inverter.




One of the great things about electronic equipment is there is no moving parts (although there is a fan in some models) so you can expect a long serviceable life from a power inverter.




Power inverters generate dangerous mains voltages so ensure the product you choose is approved for use with your mains voltage and supplier.


Power inverters can also generate electro-magnetic radiation that can interfere with other electronic equipment such as radios transmitters etc. Check for compliance with relevant standards such as C-Tick etc.




Power inverters can generate potentially lethal voltages so the utmost of care should be exercised using them to avoid accidental electrocution.




To select your power inverter carefully check the power requirements for the appliance(s) you intend to use it with.


  • Start power – Allow up to seven times for an induction motor
  • Operating power – Allow a 20% margin
  • Pure or modified sine wave


Established in 1999, Power Master is a young and rapidly growing company within DC to AC Power Inverter, AC to DC Battery Charger and UPS industry. We specialize in Modified and Pure Sine Wave Power Inverters, Solar inverter, Inverter with built in Battery Charger, On Line & Off Line UPS, and designed three stage Battery Chargers.


The company with industry integration expertise provides professional solution to accommodate customers’ specific needs in home and office appliances, mobile applications, marine, solar power applications, wind power, electronic equipment, and various applications.



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Buying a Power Inverter

On August 20, 2015, in Other, by Lambert

It might be tempting to buy a cheap power inverter, and on the face of it well it might even seem like I good idea, but if you are not careful it can quite often end up costing you more. Instead of learning the hard way here are a few things to look out for which could save you money, time and a whole lot of hassle, and a few things to consider which will help you make the right power inverter choice.

First and foremost do you really need a power inverter? If you are just interested in running your laptop from your car when you are out and about and don’t have access to a power point for example, then you are probably better off just getting a car laptop power supply as not only are these specifically designed for what you are wanting to do but also saves you having to worry about making sure you pick the right inverter for the job. On top of that they are usually around the same price as a good quality inverter so if that is all you are going to use it for then maybe have a look at what is available for your laptops make and model.

Ok, now that we have that out the way we are going to assume that a power inverter is what you want/need and so we are going to cover the main things you need to think about before clicking the buy button on a cheap and dirty power inverter. Before I go any further I just want to point out that when I say cheap I am referring to build quality, not necessarily price. While it is true you usually get what you pay for there are some very good quality power inverters out there without the hefty price tag if you do a little shopping around.

The main choice you will have to make is how high a quality power source you will need. There are two types of inverters: modified sine wave and true sine wave power inverters. Each inverter type has their pros and cons and what you end up choosing will come down to cost and the type of equipment you want to power.

You can pick up a cheap modified wave power inverter which will create a fairly choppy AC power source for a lot less than the cost of a true sine wave inverter that will replicate your homes power supply almost perfectly so it is worth having a quick think about what you want to run from it as for some appliances a cheap modified wave power inverter will do the job just fine, and save you having to fork out the extra bucks.

Having said that you will want to run a lot of electrical equipment from a high quality power source so a true sine wave power inverter is really your only option for those devices as otherwise chances are you will run into problems one way or another at some point down the track and you might even cause some serious and even irreversible damage to very sensitive equipment so it is worth making sure you pick the right inverter for the job.

For those on a budget a modified inverter is fine for most household appliances like fans, lights etc but not really recommended for more sensitive equipment. You can probably get away with running a lot of devices from a cheap power inverter and if they are not that expensive then maybe you think it is worth the risk but bear in mind you might end up damaging or reducing the life of that equipment, and could end up costing you more than what it would have cost you to buy a pure sine wave power inverter in the first place.

If you can afford it you can’t really go wrong with getting a pure sine wave inverter and it will give you the option of being able to power a far greater range of appliances and electrical equipment down the track without a worry, even if you don’t want to run them now.

If you are looking for a high quality power inverter at a great price then we have a great range of inverters to suit any application. Whether you are looking for a power inverter to run a small appliance from your car or a large inverter to power a host of electrical appliances from your car, 4WD, caravan or RV we can help with our great range of high quality great value power inverters.

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