Universal Electric Motor
Wiring Diagrams of Fractional Horsepower Electric Motors
Split Phase Induction
Split Phase Permanently Connected Capacitor
Split Phase Capacitor Start
Split Phase Capacitor Run
Another Split Phase Capacitor Run
Split Phase Capacitor Run Induction (Reversible)
Split Phase Single Value Capacitor (Dual Voltage Type)
Repulsion Start Induction (Reversible)
Skeleton Type Shaded Pole
Split Phase Induction Electric Motor This motor is equipped with a squirrel-cage rotor for constant speed operation and has a starting winding of high resistance, which is physically displaced in the stator from the main winding. In series with the starting winding is a centrifugal starting switch which opens the starting circuit when the motor has attained approximately 75 to 80 percent of synchronous speed. The function of the starting switch is to prevent the motor from drawing excessive current and also to protect the starting winding from excessive heat. The motor may be started in either direction by reversing either the main or auxiliary (Starting) winding. These motors are suitable for oil burners, blowers, business machines, buffing machines, , etc. grinders
Split Phase Permanently Connected Capacitor Electric Motor This too has a squirrel-cage rotor with a main and starting winding. A capacitor is permanently connected in series with the auxiliary winding. Motors of this type start and run with a fixed value of capacitance in series with the starting winding. The motor obtains its starting torgue from a rotating magnetic field produced by the two stator windings physically displaced. The main winding is connected directly across the line, while the auxiliary or starting winding is connected to the line through the , giving an electrical phase displacement. This motor is good for direct connected drives requiring low starting torque such as fans, blowers, some pumps, etc. capacitor
Split Phase Capacitor Start Electric Motor May be defined as a form of split-phase motor having a capacitor connected in series with the auxiliary winding. The auxiliary circuit is opened by the centrifugal switch when the motor reaches 70 to 80 percent of synchronous speed. Also known as a capacitor-start, induction-run motor. The rotor is a squirrel cage. The main winding is connected directly across the line, while the auxiliary or starting winding is connected through a capacitor which may be connected into the circuit through a transformer with suitably designed winding’s and capacitor of such values that the two windings will be approximately 90 degrees apart. Motors of this type are suited for air conditioning and refrigeration applications, , etc. belt driven fans
Split Phase Capacitor Run Electric Motor This type of motor has a running capacitor permanently connected in series with the auxiliary winding. The starting capacitor is in parallel with the running capacitor only during the starting period. The motor starts with the centrifugal switch closed. After the motor reaches 70 to 80 percent of synchronous speed, the starting switch opens and disconnects the starting capacitor. The running capacitor is usually of the paper-spaced oil filled type normally rated at 330 volt AC for continuous operation. They can range from 3 to 16 micro-farads. The starting capacitor is generally of the electrolytic type and may range from 80 to 300 micro-farads for 110 volt 60 HZ motors. These motors are good for applications requiring high starting torque such as compressors, loaded conveyors, reciprocating pumps, refrigeration compressors, etc.
Another Split Phase Capacitor Run Electric Motor This type of motor utilizes a capacitor transformer unit.and is of the split phase squirrel cage type with the main and auxiliary winding’s physically displaced in the stator. It uses a single pole double throw type transfer switch to impress a high voltage across the capacitor during start-up. After the motor has attained a speed of 70 to 80 percent of synchronous, the transfer switch operates to change the voltage taps on the transformer. The voltage supplied to the capacitor by means of the transformer can vary between 600 and 800 volts during start-up. For continuous operation, around 350 volts is furnished. Good for high starting torque applications such as compressors, loaded conveyors, reciprocating pumps, refrigeration compressors, etc.
Split Phase Capacitor Run Induction Electric Motor (Reversible) When the reversing switch is in the “B” position, the auxiliary winding becomes the main winding and the main winding becomes the auxiliary. In the “A” position the winding’s function as shown in the diagram. In split phase motors, changing the winding causes the motor to work in reverse. Both winding’s must be identical as to size of wire and number of turns. Use this when you need a reversible high-torque, intermittently rated capacitor type motor.
Reactor Start Split Phase Induction Electric Motor This motor is equipped with an auxiliary winding, displaced in magnetic position from, and connected in parallel with the main winding. The reactor reduces the starting current and increases the current lag in the main winding. At approximately 75% of synchronous speed, the starting switch operates to shunt out the reactor, disconnecting the auxiliary winding from the circuit. This is a constant speed motor and is best for light running machines such as fans, small blowers, business machines, grinders, etc.
Split Phase Single Value Capacitor Electric Motor (Dual Voltage Type) This motor has two identical main winding’s arranged for either series or parallel connections. With the main winding’s connected in parallel, the line voltage is usually 240. When the main winding’s are connected in series, 120 volts is used. The auxiliary starting winding is displaced in space from the main winding by 90 degrees. It also has a centrifugal switch and starting capacitor. This type of winding arrangement gives only half as much starting torque at 120 volts as on a 240 volt connection.
Repulsion Electric Motor By definition this is a single phase motor which has a stator winding arranged for connection to the source of power and a rotor winding connected to a commutator. Brushes and commutators are short-circuited and are placed so that the magnetic axis of the rotor winding is inclined to the magnetic axis of the stator winding. It has a varying speed characteristic, a high starting torque, and moderate starting current. Due to its low power factor except at high speeds, it can be modified into a compensated repulsion motor, which has another set of brushes placed midway between the short-circuited set and this added set is connected in series with the stator winding’s.
Repulsion Start Induction Electric Motor (Reversible) A repulsion start induction motor is a single phase motor having the same winding’s as a repulsion motor, but at a predetermined speed the rotor winding is short- circuited or otherwise connected to give the equivalent of a squirrel cage winding. This motor starts as a repulsion motor, but operates as an induction motor with constant speed characteristics. It has a single-phase distributed field winding with the axis of the brushes displaced from the axis of the field winding. The armature has an insulated winding. The current induced in the armature is carried by the brushes and commutator resulting in high starting torque. When nearly synchronous speed is reached, the commutator is short-circuited so that the armature is then similar in its functions to a squirrel cage armature. The diagram depicts a reversible type that has two stator winding’s displaced as indicated. Reversal of the motor is accomplished by interchanging the field winding connections.
Shaded Pole Electric Motor A shaded pole motor is a single phase induction motor provided with an auxiliary short-circuited winding or winding’s displaced in magnetic position from the main winding. There are a number of different construction methods used, but the basic principle is the same. The shading coil consists of low resistance copper links embedded in one side of each stator pole, and are used to provide the necessary starting torque. When the current increases in the main coils a current is induced in the shading coils that opposes the magnetic field that is building up in part of the pole pieces they surround. When the main coil current decreases, that in the shading coil also decreases until the pole pieces are uniformly magnetized. As the main coil current and the pole piece magnetic flux continue to decrease, current in the shading coils reverses and tends to maintain the flux in part of the pole pieces. When the main coil current drops to zero, current still flows in the shading coils to give the magnetic effect which causes the coils to produce a rotating magnetic field which makes the motor self-starting. Used where the power requirements are small such a in clocks, instruments, , small fans, etc. hair dryers
Skeleton Type Shaded Pole Electric Motor Built for applications where the power requirements are very small. The field circuit with its winding, is built around the conventional squirrel cage rotor and consists of punchings that are stacked alternately to form overlapping joints in the same manner that small transformer cores are assembled. Motors like this will only operate on alternating current, they are simple in construction, low in cost, and extremely rugged and reliable. Their principal limitations are however, low efficiency and a low starting and running torque. A shaded pole motor is not reversible unless shading coils are provided on each side of the pole, and means for opening one and closing the other coil are provided. The inherently high slip of a shaded pole motor makes it convenient to obtain speed variation on a fan load, for example by reducing the voltage.
Universal Electric Motor A universal motor is designed to operate on either alternating current or direct current (AC/DC). It is a series wound motor. It is provided with a field winding on the stator which is connected in series with a commutating winding on the rotor. Commonly manufactured in fractional horse-power sizes. Full load speeds generally range from 5000 to 10,000 RPM’s with no-load speeds from 12,000 to 18,000 RPM’s. Typical uses are in portable tools, office appliances, electric cleaners, kitchen appliances, sewing machines, etc. The speed of universal motors can be adjusted by connecting a resistance of proper value in series with the motor. This makes it suitable for such applications such as sewing machines that operate over a range of speeds. Universal motors may be either compensated or uncompensated, the latter type being used for the higher speeds and lower ratings only. Reversal of this motor is accomplished by an interchange of the brush holder leads, with the armature connected off neutral. In the split-series, three-wire reversible type universal motor, one stator coil is used to obtain one direction and the other stator coil to obtain the other direction with only one stator coil being in the circuit at a time. The armature connections must be on neutral in order to obtain satisfactory operation in both directions of rotation.