A single-phase induction-type energy meter's fundamental operation is limited to two mechanisms: The rotation mechanism of an aluminum disc, which is designed to revolve at a speed proportionate to the power. System for measuring and showing the quantity of energy transmitted by a circuit, such as electricity meters used in houses and businesses. The device consists of a dial that indicates the amount of energy being used, and a pointer attached to a spring. As the motor turns, the pointer moves across the face of the dial, indicating how much energy is being consumed.
The induction-type energy meter works on the same basic principal as a clock. There is a fixed magnetic field that spins at a constant speed. When a conductor such as a copper wire enters this magnetic field, it becomes imbalanced because some parts of the conductor are entering the field while others are leaving it. This imbalance creates a voltage difference between the ends of the conductor. By using two such conductors connected to each other with their open ends facing outwards from each side of the motor, a complete circuit can be made. As long as there is current flowing through one of these conductors, the other will remain magnetized, allowing energy to be measured over time. The more current that flows through the conductor, the faster the motor spins and the more the dial rotates. Energy is measured in units called "joules".
The electromechanical induction meter functions by electromagnetic induction on a single-phase alternating current source by counting the revolutions of a nonmagnetic, but electrically conductive, metal disc that is forced to revolve at a speed proportionate to the power going through the meter. The direction of rotation is indicated by a pointer attached to the disc. When the disc rotates clockwise, the pointer points to 12 o'clock; when it rotates counterclockwise, the pointer points to 6 o'clock.
Induction meters were first developed in the early 20th century and are still in use today. They are particularly useful for measuring low currents because no moving parts other than the disc and pointer are used to indicate voltage or current. This makes the induction meter immune to noise and vibration that can cause other types of ammeter readings to change.
There are two main types of induction meters: magnetic and electric. Both work on the same basic principle, but they use different components to do so. In both cases, a coil of wire is used as the core around which the disc is mounted. One end of the coil is connected to a voltage being measured while the other end goes to a pointer or dial indicator. As current passes through the coil, a magnetic field is created around the coil. The more current there is, the more the field will expand out from the coil.
A watt-hour meter is another name for a single-phase induction-type energy meter. It is given this name. This article is only concerned with its construction and operation. Other names for this type of meter include current transformer, current sensor, electric power meter.
There are two types of watt-hour meters: magnetic and electronic. The magnetic type uses a moving coil or magnetoresistive device as an indicator. The electronic type uses semiconductor devices such as diodes or transistors. Electronic watt-hour meters are more accurate than their magnetic counterparts but are also more expensive. They can also measure voltage when used with a current clamp or divider circuit. Magnetic watt-hour meters are less accurate but do not require a ground connection. They also tend to be cheaper alternative models of electronic watt-hour meters.
Single-phase induction meters usually measure both voltage and current from one conductor (hot wire), although some models may have separate terminals for each parameter. Thus, they can measure both active power and reactive power consumed by a load. Active power is the product of voltage and current, while reactive power is the product of voltage and angle between voltage and current.
Induction meters work on the principal of electromagnetic induction. An electromagnet is placed near a conductor carrying current.