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Generator Basics
  • Basic Electricity
  • Phase
  • Output
  • What size do I need?
  • Power Quality

Generator Operations

A generator converts mechanical energy into electrical energy. Electricity is commonly described in terms of voltage, amperage and watts.
  • Voltage - The electrical pressure, or force, that causes current to flow in the circuit
  • Amperage - The amount of electrical charge, or current flowing in the circuit
  • Watts - A measur of electrical power.
In an electric circuit, if there is pressure (voltage), and a path provided, then electricity will flow (current) through the conductor. Voltage is the force that causes elecctricity to flow through wires, while current is the movement of electricity.

Direct Current

Direct Current (DC) is an electrical charge that flows in one direction through a circuit. It is commonly used in consumer goods such as radios and automobiles. Dry cells and batteries are some other common sources of direct current.

A direct current source is marked with plus (+) and minus (-) symbols that indicate the direction of current flow in the circuit. The theory behind direct current holds that it flows from the positive (+) terminal, through the circuit and returns to the negative (-) terminal of the power source.

Alternating Current

Alternating current (AC) changes its direction of flow at regular intervals and is found in all residential, commercial and industrial applications.

Utility companies generate electrical power at several thousand volts and send it hundreds of miles. It is converted to higher and lower values through transformers.


The rate at which alternating current changes direction determines its frequency. Each time the curent goes one way and then the other way is called a cycle. Frequency is the number of cycles that occur in a single time period.

Frequency is also commonly referred to as Hertz (Hz) or CPS (cycles per second). One Hz is equal to one CPS. In the Untied States standard houshold current is 60 Hz, while many foreign countries use 50 Hz current.

In the construction industry 180Hz "high-cycle" current is used to power certain power certain concrete vibrators (referred to as "High-Cycle Vibrators").


Phase is a term applied to designate the circuits of an AC system. In the single-phase system, the voltages are in the same time phase in all parts of the system. In the three-phase system, the voltages are 120° apart.


Single-Phase power can be transmitted by either a two-wire circuit or a three-wire circuit. The single-phase two wire method is the simplest and most commonly used. The voltage associated with this method is 120V AC and is used to power lamps, small motors, hand tools and appliances.



Three-Phase power is transmitted by three hot wires with one ground. It is more versatile than single-phase power and is commonly used in industrial and commercial applications. One reason for this is a three-phase motor is easier to start and more efficient than a single-phase design. It is not used in residential applications.

Construction equipment typically uses either single phase or three phase motors. The contractor should specify the phase required for the job. CESSCO carries full-lines of generators that provide both single and three-phase power.

Continuous Output vs. Maximum Output:

Output references power from the generator

Continuous Output: Refers to the total wattage put out by the generator over a long period of time. Frequently refered to as "rated" output, it takes into account the effects of heat on generator efficiency. When sizing a generator, continuous output is more important than...

Maximum Output: The total wattage put out by the generator over a short period of time. Once the generator has been running for about 5 minutes the heat created by the machine will lower the electrical output.

Starting Amperage vs. Running Amperage:

There is also a difference between starting amperage and running amperage.

Starting Amperage is the amount of amps required to start an electric motor when you select a generator the Maximum Amperage should be larger than the Starting Amperage of the equipment you are powering.

Running Amperage is the is the amount of amps required to continuously run a motor. Continous Amperage of the generator you select should be larger than the required running amperage of the equipment you are going to power.

Generator Sizing:

The first thing you will need to do is determine what type of load you will be using with your generator. There are two types of loads:

Resistive Load: or Reactive Loads are devices that use a heating element and require the same amount of power to start as they need to run. Examples include:

  • Light Bulbs
  • Heaters
  • Toasters
  • Irons
  • Skillets

Inductive: or Capacitive, loads are devices that use an electric motor and require more wattage to start up than for continuous operation. Examples include:

  • Concrete Mixers
  • Submersible Pumps
  • Air Compressors

Next determine the voltage, amperage, and wattage of the tools that will be ran off of the generator. With this information you can easily determine the total wattage requirement of the equipment being used. This is accomplished by using the...

Power Formula:

Use this formula to determine your needs

Volts x Amperage = Watts

When sizing a generator, choose a unit that has a continuous output equal to or preferably greater than the total wattage requirement of the equipment. It is often a good idea to provide a little more power than what is actually required. This will give you a little more versatility once your using the generator. You may find the need to run more equipment than you initially expected and will appreciate the extra power.

Sizing with the "One - Two - Three" method:
  • One: Use this method exclusively with resistence loads (heaters, light bulbs, toasters, etc). Simply total the wattage of all items being powered by the generator, for example:
    • 29 Light bulbs @ 100 watts each = 2,900 watts.
  • Two: For items such as drills and other power tools, take the total wattage and multiply it by two. These tools will typically require up to twice the power to start than run under load. Example:
    • 1300 Watt circular saw. Multiply the running wattage (1300) x 2 in order to determine the starting watts required = 2600 watts.
  • Three: Equipment with bolted down motors (mixers, compressors etc.) multiply running wattage by three.
Power Output Quality:
  • Brushless: Among the most common in the industry because of their inexpensive construction, but have the least reliable voltage control. Brushless generators can't react to a changing load, either producing low power (a brownout) or high power. Fluctuation of this nature can casue equipment damage.
  • AVR (Automatic Voltage Regulator): Many Honda generators feature an automatic voltage regulator (AVR) designed to consistently control voltage. The AVR keeps the output voltage more constant, regardless of the load. This means no spikes or brownouts.
  • DAVR (Digital Automatic Voltage Regulator): Many Honda generators feature a new DAVR. The DAVR is designed to hold the voltage stability within a +/- 1% change during operation to the U.S. standard (60Hz). The DAVR adjustments are driven off the main winding, versus a sensor winding in convention AVR systems. Additionally, new DAVRs are protected from overheating by a thermistor.
  • iAVR (Intelligent Automatic Voltage Regulator): Some EM and EB series generators now offer the new Honda exclusive technology iAVR. This consists of a digital capacitive discharge ignition, a self-tuning regulator governor, a current transformer applied to the auto throttle and the new DAVR control unit. iAVR lets the generator operator operate well above its maximum rating for up to 10 seconds to start high initial amp draw situations. This ensures a consistent flow of power regardless of the load, which translates into protection for sensitive equipment and reliable power for you.
  • CycloConvter: Honda's patented CycloConverter technology allows you to get cleaner power with less weight. The CycloConverter offers the benefits of AVR-type generator at a lower size and weight.
  • Inverter: Produce the cleanest power of all. These units are ideal for sensitive electronics such as computers. Inverter generators offer a number of other benefits, including less noise, lower weight, and greater fuel efficiency with Super-Quiet EU series.