Elevators, conveyor machines and industrial belts, milling machines and lathes, pumping equipment... Variable speed drive applications are numerous and very visible on a daily basis, both in the industrial and in the common environment.

Also known by the acronym ASD, which respond to their name in English ('Adjustable-Speed Drive', Variable Speed Drive), these are devices or sets of them that are used for Managing the speed reached by an engine in its spinning action.

Although their application also covers other types of rotating machinery, they are mostly used in motors.

You may be interested in: Guide to avoiding annoying noises and vibrations in your reducers [Ebook]

What is a variable-speed drive or variable-speed drive

Un Variable speed drive is the equipment used in electromechanical drive systems for Control the speed and torque of the motor From CA by varying the frequency and input voltage of the motor. The variators of Speed can be: electrical, hydraulic, mechanical or even electronic.

Thanks to them you can Control the speed at which an engine operates in a precise and consistent way. Otherwise, the machinery that uses these mechanisms and motors would work according to its own characteristics and with the supply it received, which could be highly ineffective.

Variable speed drives are equipment used in electromechanical drive systems to control the speed reached by a motor in its rotating action

In addition to industrial applications, speed reducers for electric motors are also used in air conditioning equipment, large fans or industrial filling machines.

Many of the existing variable speed drives they operate thanks to two devices: an electric motor and the controller that regulates its speed.

In this way it becomes possible Alter the speed until we reach the one that is most interesting and efficient at all times, and in addition to doing so on a continuous basis, regardless of the system of stepper motor.

El speed regulator for motors has an important security component, since Control the maximum speed which can reach the engine at a specific time, preventing it from reaching too many revolutions, something that can damage the engine as well as being inefficient.

To learn more: Which motors are better for high speeds: stepper motors or servo motors?

What types of variable speed drives exist

Mechanical variators

• Adjustable pitch variator. This type of variable speed drive uses bands and pulleys.

The diameter of at least one of them can be changed to obtain the most efficient relationship between the two.

• Variable traction drive. Los metal rollers of this type of speed controller are responsible for transmitting power.

At the same time, moving them changes the transmission ratio of the contact areas they have, or between the input speed and the output speed.

Electric-electronic variators

• Variable frequency drives or inverters for alternating current (AC) motors. Both synchronous motors and induction motors are used, whether they are wound rotor or asynchronous squirrel cage motors.

In the case of synchronous motors, the regulation is carried out by adjusting the frequency supplied to the motor.

• Variable speed drives for direct current (DC) motors. Although these types of drives consist of both an electric motor and a controller, only electrical controllers are often referred to as variators.

With these devices, it is possible to control the speed at which serial direct current motors, permanent magnets, shunt and composite motors work.

• Eddy current variable speed drives. This type of variator consists of a motor that has a fixed speed and an Eddy current clutch. Two rotors, one with fixed speed added to the motor, and the other with variable speed, are part of the clutch.

Its operation is based on the regulated actuation of a field coil, which generates a magnetic field that is transmitted to the input rotor, and this in turn transfers it to the output rotor.

The greater the intensity generated by the magnetic field, the greater will also be the speed and torque transmitted. An AC tachometer will monitor the output speed.

• Sliding variators. This type of variable frequency drive has few applications today because it has been surpassed in efficiency by others.

Nowadays, variable speed drives can be used for wound rotor induction motors.

Hydraulic variators

• Hydrodynamic variator. The hydrodynamic variable speed drive, also known as hydraulic coupler for variable filling, communicates by means of mechanical torque an output rotor with an input impeller using hydraulic oil.

The input impeller must be on a constant speed axis, while the output rotor will work on an adjustable speed axis.

• Hydrostatic variator. The hydrostatic variator allows speed control thanks to a control valve. It consists of a hydraulic motor accompanied by a hydraulic pump, both with positive displacement.

A predetermined relationship is established between each revolution of the motor or pump and the volume of the fluid being used at any given time.

Another way this device offers to regulate revolutions is by changing the displacement of the motor or pump.

• Hydroviscous variator. These variable speed drives use both input and output discs which are separated by an oil film.

These connect and The torque is responsible for carrying out the transmission by means of the oil film.

Thus, the torque that is transmitted is known and is predictable, since it responds in proportion to the pressure that the hydraulic cylinder is exerting on the discs.

Advantages of using gearmotors

El use of gearmotors for very diverse types of machinery, it is justified by the large number of advantages they offer:

• Control the speed at which a motor works allows you to extend its lifespan because sudden operations are avoided, something that can cause serious damage in the long term.
• Variable speed drives and speed reducers for electric motors allow a use of motors with high efficiency; the production rate is adjusted at all times.
• To this we must add that The performance is maximum with regard to consumption, since it can be operated at different speeds for each phase, instead of a single constant, and always performing operations with smooth changes of revolutions.
• The control of the Engine torque It favors the energy savings.
• A gearmotor also makes it easy to carrying out checks, tests and adjustments by reducing the revolutions for this purpose.

In the automotive sector gearmotors are very useful in the field of security when a load change occurs or when working under vacuum. The reason is that they can prevent an excessive amount of fuel from being injected into the engine's cylinders, so that the revolutions, instead of undergoing sudden changes, are kept within constant variables.

In CLR we have a team of engineers who are experts in helping you optimize your automotive projects and projects in any sector. Contact us and we'll help you make your engineering project a reality in the best possible way.