**Power-Apparent: Apparent power is the product of voltage and current in**

**a circuit in which voltage and current reach their peaks at different times.**

**In other words, there is a phase angle between the voltage and current.**

**Apparent power is measured in volt-amperes.**

**Power-Reactive: Reactive power, also called wattless power, is q easured**

**in terms of voltampere-reactive (VAR). Reactive power increases as power**

**factor decreases and is the component of apparent power that does no real work**

**in the system.**

**Power-Real: Real power is the component of apparent power that**

**represents true work in an alternating current circuit. It is expressed in**

**watts and is equal to apparent power times power factor.**

**Signal-Analog: An analog signal is a voltage or current signal that is a**

**continuous function of the measured parameter. Analog signals provide direct,**

**instantaneous information. It is most often used for onsite monitoring with**

**meters and pen chart recorders. If analog signals are to be transmitted over**

**long distances, the signal is generally converted into a numerical value**

**before transmission.**

**Signal-Digital: A digital signal (numerical display) is pulse generated**

**and discrete. Systems used for transmission are RS-232, 4-20 ma, and 1-10**

**volt.**

**Time-of-Use Charges: Many utilities adjust energy charges for the**

**time-of-day or time-of-year that energy is used. For time-of-day billing,**

**onpeak energy costs will be higher than midpeak and offpeak costs. Other**

**utilities have established winter and summer rates.**

**Volt (E or V):**

**Unit of electromotive force.**

**Unit of apparent power; EI (single phase); E x I x**

**Volt Amperes (VA):**

**1.73 (3 phase).**

**Watt (W): Unit of true or real power; VA x p-f.**

**3. ELECTRIC METERS AND BILLING . In charging for electric energy, utility**

**companies use three types of meters. These are demand, power factor, and**

**watthour meters. Total energy charges are obtained from a watthour meter,**

**power factor from a power factor meter, and demand values from a demand**

**meter. Typically, watthour and demand meters are combined.**

**3.1 Total Energy Charges. The total energy used on an installation is**

**recorded on watthour meters and is billed in kilowatthours. The greater the**

**wattage of electrical devices, the higher the charges for total energy. Any**

**method that reduces the time of operation or the power used by an electrical**

**device will result in decreased energy charges. Many manufacturers now**

**produce products that use significantly less energy, but perform essentially**

**the same tasks as higher powered equipment.**

**9-5**