Power Inverter FAQ

What is an inverter?

An inverter transforms DC power stored in batteries into standard household AC power, allowing you to supply AC-powered appliances not having to rely on a noisy generator. See also AC, DC

Why should I use a Pure Sine Wave inverter instead of a Modified Sine Wave inverter?


There are very good reasons to choose Pure Sine Wave (PSW) or True Sine Wave (TSW) inverters over Modified Sine Wave (MSW) inverters:
  • Output voltage wave form is PSW with very low harmonic distortion and clean power, just like utility-supplied (grid) electricity
  • MSW work acceptably with resistive loads (ex. bulbs) but not with inductive or capacitive loads
  • Inductive loads like MW ovens and motors run faster, quieter and cooler. With MSW appliance may use 20% more power than it would if using a PSW. This extra power usage may damage or shorten the life of the appliance
  • Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, Game consoles, Fax
  • Prevents crashes in computers, weird print out, and glitches and noise in monitors
  • PSW reliably powers the following devices that will normally not work with MSW inverters:
  • Laser printers, copiers, magneto-optical HDs
  • Some furnaces and pellet stoves w/ μP-control
  • Certain laptop computers
  • Digital clocks with radios
  • Some fluorescent lights w/electronic ballasts
  • Sewing machines with speed/μP-control
  • Power tools w/" solid state" power/var. speed ctrl
  • X-10 home automation system
  • Some battery chargers for cordless tools
  • Medical equipment, ex. oxygen concentrators
  • Laser printers, copiers, magneto-optical HDs
  • Some furnaces and pellet stoves w/ μP-control
  • Some appliances like MW and variable speed motors will not produce full output if they do not use PSW power
  • Other devices, particularly medical equipment may not function at all unless you use a PSW inverter
  • A TSW produces a much higher equivalent wattage compared to a MSW inverter. It is somehow believed that the more you will be using this type of inverter, the greater the variety of electrical devices and appliances you will be powering.

     

    pure sine wave inverter vs. modified sine wave inverter
    Figure above shows PSW vs. MSW

How do I choose the right inverter to power my appliances?


In order to choose the right inverter it is required to list load type and power for each appliance you intend to power:
  • For resistive loads you can choose the same power as the load, or higher.
  • For capacitive loads, depending on the load, you can choose an inverter with 2 to 5 times the load power.
  • For inductive loads, depending on the specific load, you can choose an inverter with 4 to 7 times the load power.
    For ex. say you intend to power:
  • 5 x 60W Fluorescent Lamps (capacitive)
  • 1 x 150W Hair Dryer (inductive/resistive)
  • 1 x 250W LCD TV (inductive):
    Our calculation shows you would need 700W continuous power and 900W peak power.
    In this case we would suggest an 800W inverter, which features 1600W (800W X 2) peak power.
    Always take accurate inventory of the load type and power requirement for each appliance.
    Contact us for help with selecting the right inverter.


    FAQs in ABC order:
  • Alternating Current (AC): flow of electric charge which periodically reverses direction. AC is the form in which electric power is delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave. See also DC, PSW, TSW, MSW

    • Battery considerations:
    • For small inverters (typically 300W) most vehicle and marine batteries provide enough power for 30 to 60 minutes, depending on the condition of the battery and on the power demand from your appliances. If you use the inverter while the engine is off, then start the engine every hour and let it run for 10 minutes to recharge the battery.
    • For larger inverters (500W or more) use deep cycle batteries which will give you several hundred complete charge/discharge cycles. If you use the normal vehicle starting batteries they will wear out after about a dozen charge/discharge cycles. If you do not have a deep cycle battery, we recommend that you run the engine of your vehicle when operating the power inverter.
    • When operating the inverter with a deep cycle battery, start the engine every 30 to 60 minutes and let it run for 10 minutes to recharge the battery.
    • When the inverter will be operating appliances with high continuous load ratings for extended periods, it is not advisable to power the inverter with the same battery used to power your car or truck. If the car or truck battery is utilized for an extended period, it is possible that the battery voltage may be drained to the point where the battery has insufficient reserve power to start the vehicle. In these cases, it's a good idea to have an extra deep cycle battery for the inverter (installed close to the inverter), cabled to the starting battery. It is recommended to install a battery isolator between the batteries.
    • Battery Charger: available as standalone charger, without inverter. Charge method consists of CC (constant current,), CV (constant voltage), and CF (constant float) function. Over-charge, over-temperature, and over-current features. Battery charger series: DC 12V 20A, DC 24V 10A, DC 48V 5A
      •
      battery charger inverter

    • Bypass (or Transfer): automatically transfers from grid to battery and vice versa, to keep supplying AC power to the AC appliances (or AC load). See also Priority
      • Inverter bypass

    • Cable to connect inverter to battery: as a general rule make your cable as short as possible, using the thickest wire available
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      • For small inverters (typically 300 watts) a cigarette lighter adapter works, although in practice you may not be able to draw the whole 300W depending on the quality of plug and socket. You can otherwise clamp the 300W inverter directly to a battery.
      • For larger inverters (> 500W) hard-wire directly to a battery, cable size depending on distance to battery
      • General recommendations for cable size:
      Inverter Size < 3 ft 3ft - 6ft 6ft - 10ft
      300 Watts 8 6 4
      600 Watts 6 4 2
      1000 Watts 4 2 1/0
      1500 Watts 2 1 3/0
      2000 Watts 1/0 2/0 250
      2500 Watts 1/0 3/0 350
      3000 Watts 3/0 4/0 500

      Contact us to help you select the right cable size.

    • Charger option: available as option for an inverter, it includes the Bypass feature as well. See also Battery Charger and Bypass

    • Direct current (DC): is produced by sources such as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. The electric current flows in a constant direction, distinguishing it from alternating current (AC). See also AC

    • Efficiency: percentage of the power that comes into the inverter comes out as usable AC current. Efficiency of CNBOU inverters is as follows:

      • DC input 12V DC Input 24V DC Input 48V or higher
      88% 90-92% 94%

      *Efficiency = Pout / Pin x 100% = [(Vout x Iout) / (Vin x Iin)] x 100%

    • Environmental qualifications: RoHS

    • Failure rate (MTBF): less than 3%

    • Generator: with a generator, we recommend the charging-inverter series. The generator in place of the grid. In case of low battery, the generator output is connected directly to the AC load and to the battery for charging, both at the same time
      •

    • LCD Display: an LCD display is scheduled to be released by May 2015
      •

    • Modified Wave inverter (MSW): see page #1

    • MPPT Controller: CNBOU’s new MPPT controller was released on Nov 2014 and is now available. This MPPT solar controller supports a PV input voltage range of 18V-150V, with DC outputs of 12V and 24V. It features automatic identification, meaning you just need to select the controller’s charging current in accordance with your battery capacity.


      MPPT vs PWM

      Solar controller technologies MPPT and PWM are currently available. However our data shows that conversion efficiency of PWM controllers is less than 70%, while MPPT controller conversion efficiency reaches 95 to 97%. The MPPT solar controller is typically more expensive but the corresponding solar modules are more expensive. Using MPPT controller you can reduce solar module cost, and the overall cost of your solar system.

    • Priority: with the Bypass (Transfer) option the Priority feature allows setting “Inverter” or “Grid” as priority

    • Pure Sine Wave (PSW): see explanation on page #1

    • Remote Control: remote control is available only as a custom solution for turning the inverter ON & OFF

    • Shutdown voltage: the shutdown voltage is adjustable by changing a resistor

    • Stacking: stacking feature is not available as yet

    • Time: charging-to-inverter switching time is less than 9 ms

    • True Sine Wave (PSW): see page #1

    • Vehicle applications: inverter recommended when using a vehicle battery range from 300W to 2000W.
      Battery Work hours = Battery Capacity * Battery Voltage * 0.8 / Load Power (H = AH * V * 0.8 / W)

      • Contact us for more information.