A universal motor is a special motor that runs on either single-phase AC (alternating current) power or a DC (direct current) supply. These motors typically have series-wound armatures and field windings, which result in strong starting torque. Most universal motors are directly integrated into the machinery designed to power. Most universal motors are designed to work at speeds greater than 3500 RPM. They run slower when powered by an AC source than when powered by a DC supply of the same voltage because of a higher voltage drop that occurs through AC supplies. Read More…
Leading Manufacturers
ElectroCraft, Inc.
Stratham, NH | 844-338-8114When reliability and power are a must, the universal motors you find at ElectroCraft can operate with high efficiency, low voltage, and at a low cost. Applications that our universal electric motors serve include robotics, packaging, automotive, and medical equipment. Electric motor products include the CompletePower™ Plus Universal Drive, complete with a user-friendly configurable interface. For more details, contact ElectroCraft today!
Koffler Electrical
San Leandro, CA | 510-567-0630Our specialty is electrical mechanical apparatus remanufacturing. We are the largest repairer of electric motors such as AC motors, DC motors, fractional HP motors and other small specialized equipment to 30,000 HP. In addition, we sell new electric motors (AC & DC), gearmotors and gearboxes.
Carter Motor Company
Monroe, WI | 608-325-9161At Carter Motor, some of the motors manufactured include AC universal motors, small motors, DC universal motors, DC permanent magnet motors, DC shunt wound motors and gearmotors, along with many others. All Carter Motor products are designed and assembled in the United States by hard-working employees. From engineers to shipping clerks, the staff takes pride in every part of the process.
Dumore Corporation
Mauston, WI | 888-467-8288Dumore Corporation is a leading designer of DC motors, custom fractional horsepower motors, gear motors and universal electric motors. Our high-quality fractional motors are used in a variety of applications and markets. In business since 1913, we have continued to manufacture our custom high-quality UL listed OEM motors. Dumore DC motors and gear motors are designed for complete, cost effective customization to meet your exact requirements or work with our team for a custom solution!
Hankscraft, Inc.
Reedsburg, WI | 608-524-4341Hankscraft has been in the fractional horsepower motors industry since 1920. With our extensive background in the industry and years of experience we are a trusted manufacturer and supplier. our decades of contract manufacturing experience, have given us the knowledge and expertise to have an extensive and growing list of capabilities available for our customers worldwide.
Universal motors come in two different categories- compensated and uncompensated. Compensated motors use additional, scattered-field winding to help reduce power distortion for universal motors using AC power.
Universal Motor Mechanism
A universal motor's architecture is similar to that of a DC motor. Field poles are installed at the top of the stator. Weaved field coils are attached to the field poles. However, the stator and armature field circuits and the complete magnetic route are laminated. The rotating armature is wrapped with straight or skewed slots, and the commutator has brushes resting on it. The commutation on AC is harsher than it is for DC due to the current induced in the armature coils; hence high-resistance brushes are employed.
Due to the heating of the motor's magnetic components caused by the application of AC, typical DC motors experience eddy current losses. In addition, the motor's total efficiency is reduced due to this eddy current. Eddy current and efficiency loss from heating magnetic components are avoided in the case of universal motors, which use electromagnetic field winding in place of permanent magnets so they may operate on both power sources.
Working Principle of a Universal Motor
A universal motor can run on a single-phase AC or DC supply. The universal motor functions as a DC series motor when supplied with a DC source. A direct current produces an electromagnetic field when electricity travels through the field winding. The armature's conductors also carry the same current. A current-carrying conductor encounters mechanical force when it is in an electromagnetic field. This mechanical force, or torque, induces rotation of the rotor. The Fleming left-hand rule (make an L with your left hand, the thumb represents thrust, the middle finger represents the magnetic field, and the middle finger represents the direction of the current) is used to determine the force's direction. With AC power, it still produces a single-direction torque. The direction of the magnetic field and the direction of the armature current reverse to maintain the same direction of the force on armature conductors.
Universal Motor Speed and Load Characteristics
A universal motor's characteristics are similar to those of a DC series motor. The speed of a universal motor is very high when there is no load and very low when there is a load. Gear trains are typically utilized to achieve the desired speed on the demanded load.
Applications of Universal Motors
Numerous home appliances, such as vacuum cleaners, food, and drink mixers, domestic sewing machines, etc., employ universal motors. In addition, appliances like portable drills, blenders, and others use universal motors with higher ratings.
Benefits of Universal Motors
- Both DC and AC voltage sources can power the universal motor.
- The universal motor is less expensive when compared to other motors.
- The field and armature winding are built in sequence, allowing them to rotate at a very high speed, between 3.6K rpm and 25K rpm, just like series DC motors. Because of this, they can be employed in situations where quick rotations are required.
- Due to its small and lighter weight, the universal motor is utilized in many portable equipment devices requiring compact size.
- Power ratings for universal motors can be very high, ranging from 5W (watt/s) to 500W. The universal motor is utilized in mobile drill machines and blenders due to its higher rating and small size.
Disadvantages of Universal Motors
- Comparatively speaking to other AC and DC motors, like induction motors, universal motors produce more noise. Noise levels climb as the speed of the universal motor increases.
- The universal motor must be carefully balanced for it to operate as intended. Strong vibrations caused by even a slight imbalance may affect its ability to function properly and could eventually endanger anyone in the vicinity.
- Unlike DC motors, the universal motor is difficult to reverse its power connection such that it runs in the opposite direction and only on AC power.
- Universal motors are built similarly to series DC motors. Since a very high current will flow without any load, the motor may reach an unsafely high speed like a series DC motor. Therefore, the universal motor needs to have some load for effective speed control to be provided at startup. To accomplish this, universal motors must include a fan attached to the rotor shaft to add some load to the motor and make it more tolerant of the no-load condition, which prevents a runaway, high-speed condition.
