Glossary

Absorption Charge:
The second stage of three-stage battery charging. Voltage remains constant and current tapers as internal battery resistance increases during charging.
Alternating Current (AC):
The type of electrical power supplied by utilities or made when a generator is run. The unique characteristic of this form of electricity is that it reverses direction at regular intervals. For example, 120 Vac 60 Hz power reverses flow 60 times a second, hence the rating 60 Hz. (cycles).
Amp:
A measurement of the flow of electrical current. One amp is equal to the electric force of one volt acting across the resistance of one ohm.
Amp Hour:
One amp of electrical current flowing for one hour. Expresses the relationships between current (amps) and time. (OHMS law A=V/R)
Array:
A group of solar electric modules wired together.
Bulk Charge:
The first stage of three-stag battery charging. current is sent to batteries at the maximum rate they will accept while voltage rises to full charge level.
Current:
The rate of flow of electrical charge. The flow of amps is often expressed as current.
Direct Current (DC):
The type of electricity stored in batteries and generated by solar electric devices. Current flows in a single direction.
Electrolyte:
A conductive medium in which the flow of electricity takes place; this is the liquid found inside storage batteries.
Float Change:
The third stage of three-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level to reduce gassing (boiling of electrolyte) and prolong battery life. This is often referred to as a maintenance charge, since rather than charging the battery it keeps an already-charged battery from self-discharging.
Grid:
When used in reference to utility power, it refers to a system of electrical transmission and distribution lines.
Ground Fault Protection (GFP):
A circuit protection device that prevents the flow of electrical current to earth if a short circuit is present. Usually required in wet locations -- e.g. for outdoor, kitchen and bathroom circuits.
Hertz (Hz.):
The frequency, or number of times per second, that the flow of AC electricity reverses itself. Also referred to as cycles (see alternating current).
High Battery Protection:
A control circuit that disconnects charge current flowing to battery(s) when voltage reaches a dangerously high threshold. Prevents damage created by excess gassing (or boiling) of electrolyte.
Hydrometer:
A simple device that measures the specific gravity of battery electrolyte. Specific gravity readings express state of charge / discharge of battery.
Idle Current:
The amount of electrical power required to keep an inverter ready to produce electricity on demand.
Kilowatt (kW):
One thousand watts of electricity. Ten 100-watt light bulbs use one kilowatt of electrical power.
Kilowatt Hour (kW / h):
One kW of electrical power used for one hour. The most common measurement of electrical consumption, most grid connected electrical meters measure kW / h for billing purposes.
Light Emitting Diode (LED):
A device used to display various status functions.
Line Loss:
A voltage drop caused by resistance in wire during transmission of electrical power over distance.
Line-tie:
An electrical system that is connected to a utility distribution grid. For example, Trace SW line-tie inverters are designed to connect to and interact with utility power.
Load:
Any device that consumes electricity in order to operate. Appliances, tools, and lights are examples of electrical loads.
Low Battery Protection:
A control circuit that stops the flow of electricity from batteries to loads when battery voltage drops to dangerously low levels.
Maximum Power Point Tracking (MPPT):
Every PV (solar electric) device has a point where maximum current is delivered. MPPT electronically adjusts the output PV-device output to the maximum power point.
Modified Sine Wave:
An AC wave form (generated by many inverters) that is a pulse width modified square wave. It consists of a number of very small on/off steps rather than a fully smooth wave.
National Electric Code:
A consistent set of electrical wiring and installation standards used in the United States.
Off Grid:
An electrical system that is not connected to a utility distribution grid.
Oscilloscope:
A device that displays the wave form created by an electrical generating device such as a generator, inverter, or utility.
Overload / Overcurrent Protection:
A control circuit designed to protect an inverter or similar device from loads exceeding it output capacity. (A fuse, for example, is an overcurrent protection device.) All Trace inverters have internal circuitry to protect themselves from overload / overcurrent conditions.
Parallel Wiring:
A group of electrical devices, such as batteries or PV modules, wired together to increase ampacity, while voltage remains constant. (Two 100 amp hour 12 Vdc batteries wired in parallel will form a 200 amp-hour 12 Vdc battery bank.)
Photovoltaic System:
The components that form a solar electric generating system, usually consisting of PV modules, charge controller, circuit protectors (fuses or brakers) and batteries.
Series Wiring:
A group of electrical devices, such as batteries or PV modules, wired together to increase voltage, while ampacity remains constant. (Two 100 amp-hour 12 Vdc batteries wired in series form a 100 amp-hour 24 Vdc battery bank.)
Sine Wave:
The output wave form of an electric generator or utility. A smooth sine wave gong above and below zero is created. This wave form is also produced by sine wave inverters such as the Trace SW and CO-Sine series.
Surge Capacity:
The amount of current an inverter can deliver for short periods of time. Most electric motors draw up to three times their rated current when starting. An inverter will "surge" to meet these motor-starting requirements. Most Trace inverters have surge capacities at least three times their continuous ratings.
Transfer Switch:
A switch designed to transfer electricity being supplied to loads (appliances, etc.) from one source of power to another. (A transfer switch may be used to designate whether power to a distribution panel will come from a generator or inverter.)
Volts:
A unit of measure of the pressure in an electrical circuit. Volts are a measure of electric potential. Voltage is often explained using a liquid analogy -- comparing water pressure to voltage: a high pressure hose would be considered high voltage, while a slow-moving stream could be compared to low voltage.
Watt(s):
A quantitative measurement of electrical power. Watts are calculated by multiplying volts times amps. Using a liquid analogy, watts are similar to liquid flow such as liters or gallons. (watts = volts X amps).
Watt Hour (W / h):
Electrical power measured in terms of time. One watt hour of electricity is equal to one watt of power being consumed for one hour. (A one-watt light operated for one hour would consume one watt hour of electricity.)