1. Definition

The universal motor is a type of electric motor that can operate on either AC or DC power and uses an electromagnet as its stator to create its magnetic field. It is a commutated series-wound motor where the stator's field coils are connected in series with the rotor windings through a commutator. 

2. Characteristics

1. Wide adaptability to external power supply

Whether AC or DC; 60Hz or 50 Hz; 12V, 24VDC or 110V, 220V, 240V; In short, it can be designed to accommodate any external power supply of the motor.

2. High speed, wide speed range

Universial motor’ s RPM range is 3000 to 40000RPM. A wide speed range can be obtained by using multiple taps on the same motor. These character is exactly need by those motor used in home appliances. For example, a vacuum cleaner needs the high speed to form a negative pressure inside and outside the container to generate suction.

3. Large starting torque and small size

When the load torque increases, the universial motor can adjust its rotation speed and current, to increase its torque.

3. Application

The universal motor has wide range of adjustable speed and large starting voltage make them useful for appliances such as electric power tool, kitchen appliances and application about hairdressing and floor caring

4. Construction of Universal motor

Components of Universal motor include stator, rotor, front&back bracket and cooling fan. Stator consists of stator core and the winding which install on polar head. The functions of stator are generate field flux and support the front&back brakcet. The rotor is composed of rotor core, shaft, armature winding and commutator. Its function is to ensure and generate a continuous electromagnetic torque, and transform electrical energy into mechanical energy. The front and back bracket support the armature and fix the connection of stator and rotor. Among above component, the rotating shaft, the front and back bracket should have enough strength, to prevent the armature and support resonance phenomenon, causing vibration and danger. Generally there will be rolling or sleeve bearing in the front and back bracket.

5. Working of universal motor

Like the basic working schematic show, when current flows in the upper stator winding, it produces an electromagnetic field with a certain direction; then it go into commutator (copper head) through carbon brush. The current is then divided into upper and lower parallel branches in the rotor winding. The rotor coil that conducts the flow is forced by an external magnetic field to rotate the rotor. The copper head keeps the current in the rotor symmetrical and continuous. The current finally flows out of the other carbon brush and into the lower stator.Since the upper and lower stator coils are wound in the same direction, the magnetic fields generated by the upper and lower stator are in the same direction, which has to be consistent 

6. Wiring schematic diagram

7. Characteristics

In the work of single-phase universial motor, its load is not fixed at the rated point but changes. There are processes and changes such as starting, load, overload, blocking, shutdown, etc. The motor performance curve can fully describe the variation rule of parameters such as speed, efficiency, power factor, output power, input current and input power under rated voltage condition, when taking the output torque as the independent variable.

FIG. 3 is the test curve formed by fitting the data of input current, input power, output power and efficiency collected during the operation of the motor.

With the increase of load T, the working current I of the motor keeps increasing, and the input power P1 of the motor keeps increasing. As the working current of the motor increases, the iron core is magnetized and the stator excitation effect is continuously enhanced, the output power of the motor P2 increases. If only the influence of the iron core on the motor is considered, the motor efficiency increases gradually with the magnetization curve from the beginning of the magnetization section to the linear section. When the magnetization curve approaches saturation, the motor efficiency reaches the maximum. When the magnetization curve enters the saturation section, the magnetic energy reaches saturation, the output power of the motor P2 reaches the maximum, and the motor heat increases sharply and the efficiency decreases.

8. naming rule

XX   XX   XX   X   XXX
○1   ○2   ○3   ○4   ○5
○1 The universial motor is denoted by "HC"
○2 It is expressed by the maximum outside diameter of the motor lamination and rounded if there are decimal places
○3 To the motor lamination stacked thickness value, if there are decimal places will be rounded
○4 "M" indicates that alternating current is used
○5 The operating voltage is expressed by the Arabic number, and example 230 represents the rated voltage of 230V
For example:
HC8835M230 means the outer diameter of the motor is 88mm, the lamination stack thickness is 35mm, and the usage voltage is AC 230V