AC Motors
An AC motor is an electric motor that uses alternating current to produce mechanical energy using magnetism blended with alternating current. The structure of an AC motor includes coils that produce a rotating...
Please fill out the following form to submit a Request for Quote to any of the following companies listed on
This article takes an in depth look at fractional horsepower motors.
You will learn more about topics such as:
A fractional horsepower motor is an alternating (AC) or direct (DC) current motor that produces less than one horsepower with an output rating of 746 watts or less. The low power level of fractional horsepower motors makes them ideal for small electronics and simple consumer devices. When they are part of a large mechanism, such as a car, they continue running even if the power to the device stops.
There are many uses for fractional horsepower motors. Since they produce few vibrations, they can be used in equipment that requires exceptionally high precision. Two types of fractional horsepower motors are stepper and servo motors which allow for a precise input level. Fractional horsepower motors are widely used in robotics due to their precision and control.
Though fractional horsepower motors are very small, they have the same characteristics as larger electric motors. They are widely used since they can fit into any device. As with large electric motors, fractional horsepower motors use an electromagnetic field to change electricity into mechanical energy.
The types of fractional horsepower motors are divided by the type of current they use, how they use the current, and their design. They come in a wide variety of sizes and types. This particular aspect makes them versatile enough to fit into any application.
Brushed series motors were the first electric motors and date back to the middle of the first industrial revolution. Though brushless motors have replaced them, they are still found in certain applications. The modern brush motor has an axle, rotor, commutator, stator, magnets, and brushes.
There are permanent magnets on the outside in a brush motor and an armature that spins on the inside. The permanent magnets are the stator, and the rotating armature is the rotor. In the armature is an electromagnet that, when powered by electricity, creates a magnetic field that attracts and repels the magnets in the stator. This allows the armature to spin just 180o.
To keep the armature spinning, the electromagnet poles have to change, which is handled by brushes that change the polarity and transfer power to the commutator that powers the windings. The brush, through the commutator, makes contact with the spinning electrodes of the armature and flips the magnetic polarity.
A brushless motor is a synchronous electric motor that uses a step motor controller that creates rotation to convert electrical energy into mechanical energy. One of the differences between brushed and brushless motors is the elimination of the commutator.
The windings on a brushless motor are located on the stator, which removes the need for brushes. Unlike brushed motors with stationary magnets and spinning wires, a brushless motor has stationary wires and spinning magnets. The elimination of the brushes and commutator removes friction, decreases the amount of heat from the motor, and increases efficiency.
A permanent split capacitor fractional horsepower motor has a cage rotor and two windings, which are main and auxiliary like a split phase motor. It has one capacitor connected in series to the starting winding with another capacitor, "C", permanently connected to the circuit at the starting and running conditions. The motor operates as a balanced two phase motor with uniform torque and noiseless operation. Since the capacitor is permanently connected to the circuit and splits the single phase into a two phase supply, it is self-starting.
A reluctance motor works like a single phase induction motor with rings at both ends of the motor. Much like all electric motors, the central components of a reluctance fractional horsepower motor are its stator and rotor, which are separated by an air gap. They work with a precision rotating magnetic field by matching the speed of the rotor using the magnetic field of the stator.
The unique construction of a reluctance fractional horsepower motor makes it possible for them to deliver high density power at a very low cost. The motor concept is based on the principle that when a magnetic material is in a magnetic field, it is brought into line in a less reluctance way.
A special feature of a series fractional horsepower motor is its ability to produce high torque at start up. The winding of the motor is in a series with the armature winding, which is different from the construction of other electric motors. Large conductors in the armature and field windings offer the only resistance to the flow of the current, which is low because of their size. The size of the conductors allows them to accept a large amount of current that saturates the coils to produce a strong magnetic field.
A servo motor is a rotary motor that offers precise control of angular positioning, acceleration, and velocity. The most common use of servo motors is in a closed loop control system, such as robotics and computer numerical control machines. A servo motor uses position feedback to control rotational speed, motion, and positioning.
A control signal input determines the positioning of the shaft, which the controller corrects if the position does not meet the initial specifications. Servo motors are positioned between the input system and the process and use feedback from the process to control its positioning.
A shaded-pole motor is the simplest of AC motors and consists of a rotor assembly and stator pole. Aside from the rotor and pole, shaded-pole motors have windings that are shaded and unshaded. The shaded portion of the motor’s winding is a copper ring, which acts as its secondary winding. The unshaded winding creates a lower strength magnetic field. The magnetic flux created by the interaction of the windings increases the torque after it has started. Shaded-pole motors move in one direction and are found in washing machines.
A split phase fractional horsepower motor has a single cage rotor and a stator with two windings divided into main and starting. The windings are displaced at 90o. The main winding has low resistance and high inductive reactance, while the starting winding has the opposite with high resistance and low inductive reactance.
The resistor is connected in series with the auxiliary winding causing the current in the windings to be unequal, leading to the rotating field not being uniform. Starting torque is 1.5 to 2 times the running torque. Once the motor reaches the appropriate synchronous speed, the starting winding is automatically disconnected.
A stepper fractional horsepower motor is a DC motor that moves in steps and has multiple coils organized in phases. When the phases are energized in sequence, the motor rotates. They are normally chosen for applications that require precision motion control, such as automation and robotics.
In a synchronous fractional horsepower motor, the rotation of the shaft is the same as the applied current. The total number of rotations the shaft makes is equal to the current and is the same as the AC cycles. A synchronous motor has multiple phases AC electromagnets on the stator that produce a rotating magnetic field. A permanent magnet is synced with the rotating magnetic field.
Fractional horsepower motors are multipurpose motors used as a necessary component in a wide range of applications. They are ideal for conditions where there is limited space, but exceptional performance is essential. In the majority of cases, fractional horsepower motors are direct current motors used for precision and automated applications.
Several factors have to be considered when designing a fractional horsepower motor, with torque and speed being two of the most critical. Also included in the decision process is whether a brush or brushless motor best fits the application.
Fractional horsepower motors have an output power of 746 watts or less with a frame size of less than 104 mm2. The standard range of power for each type of motor is 1/20th hp to 1 hp for AC motors, 1/100th hp to 1/2 hp for DC motors, 1/35th to 1/2 hp for brushless motors, and 1/100th hp to 2 1/2 hp for universal style. Smaller versions of fractional horsepower motors are categorized as sub-fractional or micro motors.
Micro motors are very small and lightweight, designed for low power consumption and limited electromagnetic interference. They are purposed for compact and complex spaces where there is restricted power. Micro motors can be brushed or brushless, each of which has its advantages for specific applications.
The power supply for fractional horsepower motors can be AC or DC, with AC being single or three phase. The majority of AC fractional horsepower motors are single phase, which are shaded pole or split phase. Since a single phase motor operates on a pulsating current, it requires extra current to start the pulsating motion. Single phase motors do not have the same high efficiency levels as three phase AC motors but last longer with little need for maintenance.
DC motors can be brushed or brushless. Ones that are brushless are synchronous and use a closed loop controller to switch the DC currents.
The three factors that influence the power of a fractional horsepower motor are horsepower, torque, and speed. Horsepower is the measurement of the motor’s work while torque is the angular force it will wield. The speed of a motor refers to how rapidly the motor turns.
Speed multiplied by torque directly relates to horsepower. The power of a motor has to match the type of workload it will be performing. Though a powerful motor may seem logical, it is better to match the workload to the horsepower for the greatest efficiency.
The formula below is for the calculation of horsepower. The constant, 5252, is the conversion of James Watts' initial 33,000 foot pounds per minute into Newton (N) meters per second.
Horsepower (HP) = (Torque × Speed)/5252
The purposes of enclosures are to contain the elements of the motor and protect the mechanism from harm. There are a wide variety of enclosures, from ones made of plastic to ones made of aluminum and steel. There are ten classes of fractional horsepower enclosures, which are open drip proof (ODP), totally enclosed fan fooled (TEFC), totally enclosed air over (TEAO), totally enclosed non-ventilated (TENV), totally enclosed force ventilated (TEFV), weather proof level 1 (WP!), Weather proof level 2 (WP2), totally enclosed air to air cooled (TEAAC), totally enclosed water to air cooled (TEWAC), and Explosion Proof (XP).
Bearings are an essential part of electric motors as a method for reducing friction and wear. They allow shafts to rotate at high speed with little loss of power and replace sliding motion with a rolling motion. The two most common types of bearings are ball and cylindrical.
Ball bearings provide a rolling motion through the use of balls that are positioned in a race or cage. They are designed for high speed and low friction and can handle light to medium loads. In electric motors, they are used in direct coupled applications to handle radial or axial loads.
Cylindrical roller bearings are designed to handle heavy loads at exceptionally high speeds. They are placed in a cage that prevents them from touching and reduces friction. The high performance of cylindrical bearings is due to the increased contact surface of the bearings.
Fractional horsepower motors are used in applications that require precision and accuracy. Though they are very small, they have a highly efficient gear system capable of performing a wide range of processes with flawless consistency. Fractional horsepower motors are complex motors that are designed with skill, expertise, and knowledge.
There are endless uses for fractional horsepower motors that run the full gamut of applications, from ones engineered for dispensing medicine to ones for opening and closing doors. The many varieties of fractional horsepower motors make them adaptable to any conditions or purpose.
Fan motors have a simple construction and are synchronous or asynchronous. There are several varieties of fan motors that vary in size and type. A frequency inverter is connected to the fan motor to change the frequency and control the fan’s speed. The majority of fan motors operate on DC current.
Computers use fractional horsepower motors to turn their hard drive to spin the disk to read saved data. A necessary part of a computer is a fan that cools the components during the computer's operation. In both cases, the motors are very small and compact to fit in the computer housing but are exceptionally accurate and reliable.
There are several fractional horsepower motors in air conditioners, including a blower motor and a motor in the air compressor. The refrigerant lines are controlled by the compressor and are the core of the air conditioner. The fan of an air conditioner blows air across the condenser unit to speed up heat transfer from the refrigerant to the outdoor air.
A windshield wiper fractional horsepower motor is a small tube motor that is connected to the wiper arm. A linkage is used to connect the motor to both wiper arms. The motor is connected to the blade of the wiper by the wiper arm. When a switch in the car is activated, a signal is sent by a fuse to the wiper motor. Included in the signal is the speed at which the motor will move the arm.
There are several fractional horsepower motors used to properly position the seat for a driver or passenger. By pressing buttons located on the side of the seat, the fractional horsepower motors move the seat forward or back, up or down, position the headrest, and tilt the seat. The motors are turned on by relays responding to the signals from the seat switches.
The two types of fractional horsepower motors used in the manufacture and production of robots are DC motors and servo motors. Stepper motors are also used for specialty robotic functions. The many types of motors used in robotics control motion, including vertical, radial, rotational, pitch, roll, yaw, and movement motions.
Fractional horsepower motors are ideal for use with robotics due to their size and accuracy. The wide variety of fractional horsepower motors makes it possible to find a motor to fit any robotic function, motion, and condition.
The six applications for fractional horsepower motors listed above are a very small sampling of the multiple uses for this reliable and valuable tool. Anywhere there is a need for a small motor, it is very likely a fractional horsepower motor is being used.
An AC motor is an electric motor that uses alternating current to produce mechanical energy using magnetism blended with alternating current. The structure of an AC motor includes coils that produce a rotating...
A DC motor or direct current motor is an electrical machine that transforms electrical energy into mechanical energy by creating a magnetic field that is powered by direct current. When a DC motor is powered, a magnetic field is created...
An electric motor is an electric machine that converts electrical energy to mechanical energy. Most electric motors work via the interaction of the motor magnetic field and electrical current in a wound wire to...
Power supplies are electrical circuits and devices that are designed to convert mains power or electricity from any electric source to specific values of voltage and current for the target device...
An AC power supply is a type of power supply used to supply alternating current (AC) power to a load. The power input may be in an AC or DC form. The power supplied from wall outlets (mains supply) and...
An AC power cord is a detachable way of providing an alternating current of electric energy from a mains power supply to an electrical appliance or equipment. Serving industries like...
A DC DC power supply (also known as DC DC Converter) is a kind of DC power supply that uses DC voltage as input instead of AC/DC power supplies that rely on AC mains supply voltage as an input...
A DC power supply is a type of power supply that gives direct current (DC) voltage to power a device. Because DC power supply is commonly used on an engineer‘s or technician‘s bench for a ton of power tests...
Electrical plugs, commonly known as power plugs, are devices responsible for supplying and drawing current from a receptacle to the circuitry of an electrical appliance...
Gear drives, sometimes referred to as gear trains and gearboxes, are mechanisms consisting of an assembly of gears, shafts, and other machine elements for mounting the rotating parts...
By definition a power supply is a device that is designed to supply electric power to an electrical load. An electrical load refers to an electrical device that uses up electric power. Such a device can be anything from...
A NEMA connector is a method for connecting electronic devices to power outlets. They can carry alternating current (AC) or direct current (DC). AC current is the typical current found in homes, offices, stores, or businesses...
A power cord is an electrical component used for connecting appliances to an electrical utility or power supply. It is made from an insulated electrical cable with one or both ends molded with connectors...
A programmable power supply is a method for controlling output voltage using an analog or digitally controlled signal using a keypad or rotary switch from the front panel of the power supply...
Thomas Edison developed the power distribution system in 1882. He wrapped a copper rod in jute, a soft shiny fiber from plants, as an insulator. The jute wrapped copper rod was placed in a pipe with a bituminous compound...