Vibration that occurs due to the periodic repetition of transient phenomena when moving from one steady state to another.

Refers to the distance between the circumference of the rotor and the pole surface of the stator, or the void in the magnetic circuit.

An alternating current is an electric current whose magnitude and direction change periodically over time. Just as a clock goes back and forth in a certain rhythm, an alternating current rises from 0 to a maximum value in one direction, falls to 0, and then rises to a maximum value in the opposite direction. In other words, AC repeats the cycle that has the same positive and negative alternations.

Refers to the relationship between the direction of current flow and the direction of magnetic field generated at that time. When a right-hand screw is turned, the direction of the screw's movement is the direction of the current, and the direction of the screw's rotation is the direction of the magnetic field.

A value that represents the angle of rotation per unit time to determine the velocity of a rotating object.

A general term for the main winding of a motor or generator and the iron core that winds this winding.

In a DC or an AC generator, when current flows through the armature winding, a magnetic field is applied and the distribution of magnetic flux changes.

A device that makes brush contact with the commutator surface with an appropriate amount of pressure.

The number of series leading wires in one phase of the armature winding of the alternator

When a ferromagnetic substance is magnetized to saturation, it retains residual magnetism in the magnetized direction even when the external magnetic field is removed.

A DC motor having a series wound field winding in parallel with the armature winding and a series field winding in series with the field winding of the main pole.

Reciprocal of resistivity.

An object that does not stay in the place where electricity was applied when electricity is supplied but moves to another place.

When conductors contact each other, resistance occurs at the point of contact. When current flows through a contacted part, we can see that there is resistance in that part, which is called contact resistance.

Joule loss occurring due to the resistance of the winding among the losses occurring in electrical instruments.

When there is electromotive force, electromotive force is excited in the opposite direction of the electromotive force by Lenz's law.

A curve for evaluating the strength of a permanent magnet. The second upper limit of the magnetic hysteresis curve when magnetized to saturation.

A phenomenon wherein the field magnetomotive force is weakened due to the current in the armature winding within angle α on both sides of Y when geometric neutral axis Y and electrical neutral axis Y' are misaligned in a DC motor and the brush is positioned along the electrical neutral axis.

One of the means of distributing three-phase power to six-phase loads.

A substance that is magnetized in the opposite direction to the applied magnetic field. In other words, the side where the magnetic field lines enter becomes the N pole, and the side where they exit becomes the S pole.

When the voltage applied to the insulator is gradually increased, a rapid discharge phenomenon occurs at a high voltage exceeding the maximum value.

Direct current is a flow of electrons that flow in only one direction. Therefore, the direction, polarity, and magnitude of the charge are always constant. Direct current voltage does not change over time, and it is obtained from a battery or a DC generator.

Generally, it is used by connecting a load to the motor's rotating shaft through a belt or a gear, which is called indirect drive. In contrast, a drive method wherein the motor itself forms the driving part of the load by directly connecting the load to the motor output side is called direct drive, which is usually used when very precise rotation performance is required. Naturally, there is no backlash and no shaft wobble. This motor is usually used for the FDD, HDD, CD, and VTR.

A method for winding a single-phase coil by distributing it into multiple slots in an electrical device with slots.

Eddy current is a loop of electrical current that flows within the metal plate when a magnetic field changes as it intersects the metal plate.

Energy loss due to heat generated by the eddy current.

Refers to the amount of electricity possessed by a substance.

The time elapsed for the output current (armature current) generated when a step voltage is applied to a DC motor to reach 63% of steady state. A large electrical time constant means that it takes long to reach steady current. This ultimately means that the motor has poor rise characteristics because it cannot generate sufficient torque.

When a current flows through a conductor placed in a magnetic field, a force that moves the conductor in a direction perpendicular to the current and the magnetic field is generated, which is called electromagnetic force.

Electromotive force is generated in a coil when the magnetic flux passing through the coil changes.

The effect of raising the potential of a charge and causing current to flow in an electric circuit. The unit is [V].

An electric circuit that replaces a complex circuit using equivalent resistance, impedance, and capacitance.

Current to generate a magnetic field.

A range of magnetic force spread, which is created by an electromagnet or permanent magnet.

One of the speed control methods of a DC motor. A method of changing the rotation speed by changing the magnetic flux through field current change.

A winding installed on the excitation in a rotating machine. It is installed on the stator side in a DC machine and on the rotor side in a synchronous machine, and either one is excited by DC current.

Power loss that is not related to the increase or decrease in load current, such as iron loss and mechanical loss.

Frequency shows how many times a similar shape of alternating wave repeats itself per second. (Number of cycles per second) Frequency is represented by f and the SI unit is Hertz (Hz). Korea adopts 60Hz frequency as its standard, which means that the direction of the current changes from + to - 60 times per second.

- The gearbox uses gears to reduce the rotation speed of the motor while amplifying torque. At this time, the ratio at which the gearbox reduces the rotation speed of the motor is called the reduction ratio. - Since the reduction ratio has two series (i.e., series of 3, 5, 7.5, 12.5, 15... and series of 3.6, 6, 9, 15, 18..., which is 1.2 times the reduction ratio), the same reduction shaft rotation speed can be obtained at 50 Hz and 60 Hz. In other words, the output shaft rotation speed of the gearbox is almost the same when the reduction ratio is 3 in the 50 Hz region and 3.6 in the 60 Hz region.

Low-speed rotation or high torque generation can be achieved by attaching a gear or other reduction mechanism to the motor's rotational shaft. It is widely used in camera film winding devices, car starter motors, electric drivers, and other situations where high torque is required.

A speedometer that uses the property wherein the voltage generated by a generator is proportional to the rotational speed.

AC resistance when AC flows through an electric circuit.

Electromotive force generated by electromagnetic induction.

When the current flowing through a coil changes, a voltage is generated in that coil. The quantity that represents the ratio of this voltage.

When the stator winding of an induction motor is energized and the rotor speed increases above the synchronous speed by using another motor, the rotor winding cuts the field flux in the opposite direction to that of the motor, so the induced voltage and current become reverse to the field flux.
In the stator winding, the current flows in such a way that the magnetic field produced by the rotor winding current is canceled out. In other words, the mechanical input applied to the rotor becomes an electrical output, and current flows from the stator winding to the power source, resulting in power generation. This is called an induction generator.

When performing a circuit integral with respect to the magnetic field due to the current, when the path of integration passes through the equivalent plate created by the closed-loop current.

A type of amplifier that reverses the polarity of the input and output signals.

Iron loss occurs at the iron core of generator, motor, or transformer due to eddy current and hysteresis, since the alternating magnetic flux passes it through. To reduce this iron loss, silicon steel sheets are insulated and overlapped.

A magnetic flux that does not work effectively because it inter-links only one winding for the main magnetic flux that works effectively for electromagnetic induction between the two windings.

In transmission lines, it is about the leakage current on the surface of the insulator and the value is small. However, when corona occurs, this effect is treated as equivalent leakage inductance.

The change in leakage flux induces an electromotive force that is 90 degrees behind the main flux during winding. Its magnitude is proportional to the leakage flux. Since most of this flux passes through the air, it is proportional to the current. Therefore, when the electromotive force generated by the leakage flux is jLx, Lx is called the leakage reactance.

Refers to the voltage between neighboring wires or between terminals in a multi-phase AC circuit.

The primary and secondary sides of a synchronous motor are developed in the axial direction. A motor that converts rotary motion into linear motion.

Phase difference between single-phase, no-load induced electromotive force, and terminal voltage in a synchronous generator

Loss that occurs only when under load.

A curve representing the relationship between the exciting current and the terminal voltage when constant load is applied by operating a synchronous generator at a rated speed.

Electron motion in a magnetic field. When a moving electron enters a magnetic field, it receives a force from the magnetic field and changes its direction of motion to circular motion.

The inside of a ferromagnetic substance is divided into small regions. This small area is called magnetic domain.

A place where a magnetic force acts. In other words, a place where a force acts between currents, between magnets, or between a current and a magnet.

The magnetic lines of force coming from a unit magnetic pole are grouped together and are called magnetic flux.

A term used to deal quantitatively with magnetic phenomena, referring to magnetic flux per unit area.

When a ferromagnetic material is magnetized by applying a magnetic field from the outside, the magnetic field remains even after the magnetic field that caused the magnetization is removed (residual magnetism).

A magnetic material is magnetized by the influence of an external magnetic field.

A line connecting the same tangent direction in electric field lines and coinciding with the direction of the magnetic field.

When a bar magnet that can rotate freely around its central axis is placed in a magnetic field, the south pole of the magnet rotates toward the north pole of the magnetic field, and the north pole of the magnet rotates toward the south pole of the magnetic field. This turning force is proportional to the product of the length of the magnet and the strength of the magnetic pole. The product of the length of the magnet and the strength of the magnetic pole is called the magnetic moment.

The part of a magnet that shows the greatest magnetic force at each end.

The area in the magnetization curve where the intensity of the magnetization does not change even if the magnetic field intensity is increased.

When a magnet is close to a metal such as iron or nickel, a force is applied that attracts metal.

An object placed in a magnetic field becomes a magnet by magnetic induction.

When a coil is wound N times around an iron core with current I flowing through the core, magnetic flux ø generated in the iron core is proportional to NI. This NI is called magnetomotive force.

A semiconductor device whose resistance value changes by the strength of the magnetic field. It is used as a sensor.

When a magnetic substance is magnetized, deformation occurs; conversely, when a force is applied from the outside to deform it, the state of magnetization changes.

Loss of mechanical energy due to frictional resistance in a rotating machine.

The time elapsed for a DC motor to reach 63% of its normal number of revolutions speed when a step voltage is applied (i.e., motor starting). The larger the constant, the slower the motor will move, which ultimately means insufficient controllability.

The ability to cause rotation.

The proportional coefficient of the time variation of the primary current and the voltage induced in the secondary current in mutual induction.

A metal plate specifying the necessary information depending on the type of device.

Loss that occurs when electrical equipment is operated without any loads.

An object that causes almost no magnetic induction even in a magnetic field.

The rotating magnetic pole is not a salient pole but a cylindrical one.

Output refers to the energy emitted from the exit of a circuit or a device, with the output of a motor referring to the work that the motor can perform per unit time. The output of a motor is determined by the product of the rotational speed and the force (torque).

It describes the over-rotation of the motor in degrees (rotations) from the moment of power cut-off to output shaft stop.

Refers to the maximum torque that can be used when operating the motor. It is limited by the rated torque of the motor, temperature rise, and the strength of the combined gearhead.

Represents the phase difference of two sinusoidal AC waveforms of the same frequency in degrees.

Power consumed in an electrical circuit per unit time

In direct current, power can be simply obtained by multiplying voltage and current; in the case of alternating current, however, power is obtained by multiplying the scalar product of effective voltage V and effective current I by the cosφ of phase difference φ between the voltage and current. This cosφ is called the power factor. That is, it represents the product of voltage and current in the same phase.

 

Material of permanent magnets: The volume of the permanent magnet can be reduced when magnetic energy (B*H, where B is the residual magnetic flux density and H is the coercive force) is large. That is, a strong turning force can be obtained with a small permanent magnet. When a large magnetic force is required in small motors, rare earth magnets such as neodymium or samarium, or magnets of the barium ferrite or strontium ferrite series are widely used.

The rating of an electrical appliance or other device means the limit within which the device can be used under specified conditions. Each device is designed to operate best under its rated conditions, so be sure to pay attention to its ratings when using it. The usage limit of motors is indicated by rated output, rated voltage, rated current, rated frequency, and rated rotation speed.

In an electric circuit, only resistance interferes with direct current; in an alternating current, however, since the direction and magnitude change from time to time, there are components corresponding to the resistance component that interferes with the current in addition to resistance. This component is called reactance.

In an AC circuit containing a reactive component (X), reactive power is the product of the rms value of voltage V and the rms value of current I multiplied by the sine of the phase angle (φ) (Q).

Refers to the magnetic flux density when the magnetizing force is set to zero in the magnetization curve.

Refers to a type of rotary electrical transformer used to detect the rotation angle in a servo mechanism.

Since the values of the coil component and capacitor component are the same, it operates as if there is only the real part, i.e., the resistive component. Maximum power transfer occurs. A resonant circuit causes resonance at any frequencies.

There is a frequency at which L=1/ωC in an LC AC circuit, depending on the applied frequency, even if C is constant, which is also called natural frequency.

The part of a motor that performs rotary motion. Conversely, the fixed part is called the stator.

When the two ends of dissimilar metals are joined and a temperature difference is applied to the two bonded points, thermal electromotive force is generated, which causes a thermal current to flow in the circuit. A thermocouple is a device that uses this effect to detect temperature.

A generator that uses the method of causing the exciting current of a DC generator to flow by a self-induced electromotive force.

The constant of the coil and the proportional constant of the induced voltage. The symbol is L and the unit is [H]

A coefficient used when estimating the life of a gearhead, which is obtained with experiences based on the type of load and usage conditions. The life of the gearhead can be calculated by dividing the average life under specified usage conditions by the service factor.

Shielding to prevent electronic energy from entering a certain space or, conversely, from leaking from the inside to the outside.

Connecting with a conductor of zero or near-zero resistance.

Refers to a device installed to minimize damage by fire to generators, transformers, etc. when a short circuit accident occurs, or to prevent it from developing into other accidents.

Spacing between the coil sides of the armature coil. In other words, coil pitch wound shorter than the magnetic pole spacing.

When measuring the current of a circuit, if it is greater than the rating of the amperemeter, divide the current and then measure it by connecting a separate current in parallel with the ammeter.

A generator that excites with the voltage generated by the armature by connecting the armature winding and the field winding in parallel.

Winding method of an armature that inserts one coil side in one slot.

A single-phase AC powered motor that has a single-phase winding on the stator and a box-shaped rotor.

A groove dug into an iron core to insert the stator winding or rotor winding of a rotating machine.

A space angle or a mechanical angle is the angle expressed as 2π for one rotation of the rotor in a rotating machine.

AC has a rectangular waveform, and pulse waves also fall into this type.

Refers to the starting torque that is required to overcome inertia or load when starting a machine.

Torque generated when holding a load while the electronic brake and clutch brake are stopped.

A fixed part of the motor, generator, etc. The part that rotates in the opposite direction is called the rotor.

A motor stops because the load angle exceeds 90 degrees when the load torque exceeds the escape torque of the motor.

An alternating current generator that generates electricity at a frequency synchronized to the speed of the engine.

Synchronous reactance, effective resistance and series impedance

A motor that rotates synchronously to the frequency of the power supply for a certain range of loads.

A rotating magnetic field determined by the number of poles of the rotating magnetic field and the frequency of the AC power source.

Refers to the end of a wire that receives or transmits current. The terminal voltage is the voltage between the two terminals.

A range of allowable dimensions, since it is very difficult to finish machine parts to the instructed dimensions when machining them.

- Motor torque refers to the size of the force to turn a rotating body, and the unit of [gf•cm] or [kgf•cm] is used. The SI unit is [N.m], and some countries also use [Oz•in] or [lb•in].

Efficiency when amplifying torque by attaching a gearhead to a motor, expressed in %. Transmission efficiency is determined by the friction of bearings and gears, and the resistance of lubricating oil. Generally, transmission efficiency decreases when the number of reduction gear stages increases. Since the transmission efficiency per stage of the reduction gear is approximately 90%, transmission efficiency decreases inversely proportional to the number of stages. In other words, the efficiency is 81% for 2 stages, 73% for 3 stages, and 66% for 4 stages.

A coil of insulated copper or aluminum wire wound around a core in an electrical appliance.

A value indicating the voltage that can be withstood by a device, component, etc.