How to reduce speed of electric motor

how to reduce speed of electric motor

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Sep 06,  · BUY AmazonSpeed Reducer Gear Box: Motor Gear Box: Install a variable rheostat and you can control your motor's speed. Disconnect the single-phase motor from the power source. Use a knife and cut the wire that connects the motor to the power source. Make the cut about 12 to 18 inches away from the motor.

Adding a variable-frequency drive VFD upstream of an AC motor can lower energy ohw, reduce peak demand and improve power factor in many applications. Reducing motor speed at startup and during operation can cut maintenance costs, increase uptime and extend equipment life. Lowering motor speed when possible can reduce stress on the motor and its connected equipment. Although the primary focus of this article is to show how reducing motor speed cuts maintenance and repair costs, using a VFD can also result in substantial energy savings in certain applications.

According to the U. Calculating an average return on investment for a VFD attached to a motor can be difficult, says Kevin Schiller, an analyst who covers rotating machines and controls for IHS Technology. Schiller says additional benefits from drive attachment that can reduce the investment payback time include reducing motor stress and prolonging motor life, reducing inrush currents, and realizing regenerative savings and harmonics mitigation on drives that offer such capabilities.

In general, suppliers report that customers expect at most a 2-year return on investment when making motor system-purchasing decisions, Schiller says. Some suppliers have accordingly shifted strategies, with programs to supply the more energy-efficient equipment for free and collect payment from the energy savings realized after installation.

This is more common in retrofit scenarios, especially in building automation applications such as HVAC equipment. When considering the most frequent causes of motor failures, motor bearings and damaged stator windings rank at or near the top. Taken together, bearing and winding issues account for more than half of motor failures. Fewer motor rotations result in less wear, so reducing motor speed can increase rotor and bearing life. Operating at a lower speed also reduces dynamic and static loading, along with thermal, vibration and shock stresses.

Ramping up slowly from stop to operating speed and running motors at lower speeds increases motor life by reducing wear and tear on motor bearings, motor winding insulation and connected mechanical components. With less work, there also is less heat, which extends insulation life. Stator winding insulation life is adversely affected by heat and running a motor slower usually reduces heat load. At reduced speeds, how to reduce speed of electric motor life increases in variable torque load applications for all motor types.

When running totally enclosed fan cooled TEFC motors at a constant torque load, insulation life may decrease at low speeds due to temperature rise, so it motorr possible to mtor too slowly.

Every process, conveyor and equipment application has an optimum speed at any given point in time. This optimum speed may be expressed in gallons per minute, inches per second, parts hwo minute and so on. Maintaining speed close to this optimum point can help cut maintenance costs. A VFD offers the ability to adjust the amount of work being done to match the load.

Hkw processes require adjustment of flow or pressure. An AC drive with proportional integral derivative PID control can control the speed of a pump and consequently flow or pressure.

This speed fo may be more efficient than a flow control valve dumping excess flow back to a tank. The ability of an AC drive-controlled system to reduce motro total flow or pressure delivered also allows a smooth rate of change, reducing, for example, the water hammer effect that can stress motors, pumps, valves and process piping.

Unnecessarily high motor speed affects any equipment the motor is attached to. Mechanical systems and power transmissions benefit from lower loads and stresses. It is easy to see the effect of too much speed on a ball screw in a linear actuator as running it too fast can cause the screw to bow and oscillate.

Other types of electrjc effects can occur due to excess speed in mechanical systems such as pumps, fans and transmissions. Custom equipment, such as a multi-station rotating table, must meet cycle time requirements. Running the table and related actuators faster than necessary can increase wear to the motion control components such as couplings, bearings, rollers, ball screws and gearboxes.

Controlling the rotating table motors to run at only the required speed can also improve long term accuracy and durability. Dynamic stresses, such as high acceleration and deceleration rates, regardless of speed, cause a variety of maintenance problems such as bearing failures and breakage of couplings, belts how to reduce speed of electric motor chains in production equipment. Across-the-line starts are harder on the motor what to do with old cables the electrical system than a hlw start.

Starting and stopping are the most stressful parts of motor operation as they cause high dynamic stress, and frequent starts s;eed stops can increase motor temperature. An AC drive not only can control operating speed, but it can also reduce motor acceleration and deceleration rates.

This reduces wear on belts, reducee, chains, clutches, shafts and bearings. With this feature, the output voltage is lowered in relationship to the output frequency. In lightly loaded applications, this reduced voltage cuts excitation loss in the motor and reduces motor current, eectric thermal stress without sacrificing speed.

The low voltage drives research is accessible here. Energy efficiency is also discussed in this IHS report on low voltage motors. Researchers discover material for photoactuator manufacturing.

Kaltra extends its range of air-cooled how to sync folders in vista. Couplings offer concentricity for precision applications. GlobalSpec collects only the personal information you have elcetric above, your device information, and location data. GlobalSpec may share your personal information and website activity with our clients for which you express explicit interest, or with vendors looking to reach people like you.

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An error occurred while processing the form. Please try again in a few minutes. Source: National Renewable Energy Laboratory. Add your comment. Understanding variable frequency drives and applications. Motor Makers Tackle the Efficiency Challenge. Materials and Chemicals.

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Sep 17,  · Lowering motor speed when possible can reduce stress on the motor and its connected equipment. Whether the application is a process pump, a material handling conveyor or a piece of automated equipment, maintenance can be reduced by calculating and limiting a system’s maximum necessary speed, and by smoothing acceleration and deceleration when starting and stopping. When the variable resistor reaches its minimum value, the armature resistance is at a normal one, and therefore, the armature voltage drops. When the resistance value is gradually increased, the voltage across the armature decreases. This in turn leads to a decrease in the speed of the motor. 5 Answers5. Voice of experience: Use a jackshaft and additional belts/pulleys, &/or change to a different motor (DC with DC speed controller or 3-phase + VFD (variable frequency drive) variable speed.) The DC motor and speed control can often be salvaged from a treadmill that someone gave up on using, for free.

In the period of the 18 th century itself, there was the evolution of DC motors. The development of DC motors has widely enhanced and they are significantly applied in multiple industries. In the early period of the s and with the enhancements made in the year , DC motors were initially developed by the British researcher Sturgeon. He invented the initial commutator type of DC motor where it has the capability to simulate machinery too.

But one might wonder what the functionality of the DC motor is and why it is important to know about DC motor speed control. So, this article clearly explains its operation and various speed controlling techniques. A Dc motor is operated by using direct current where it transforms the received electrical energy into mechanical energy.

This triggers a rotational change in the device itself thus delivering power to operate various applications in multiple domains. DC motor speed control is one of the most useful features of the motor. By controlling the speed of the motor, you can vary the speed of the motor according to the requirements and can get the required operation. The speed control mechanism is applicable in many cases like controlling the movement of robotic vehicles, movement of motors in paper mills, and the movement of motors in elevators where different types of DC motors are used.

A simple DC motor works on the principle that when a current-carrying conductor is placed in a magnetic fiel d, it experiences a mechanical force. In a practical DC motor, the armature is the current-carrying the conductor and the field provides a magnetic field.

When the conductor armature is supplied with a current, it produces its own magnetic flux. The magnetic flux either adds up to the magnetic flux due to the field windings in one direction or cancels the magnetic flux due to field windings. The accumulation of magnetic flux in one direction compared to the other exerts a force on the conductor, and therefore, it starts rotating.

Thus, a DC motor has a very special characteristic of adjusting its torque in case of varying load due to the back EMF. Speed control in the machine shows an impact on the speed of rotation of the motor where this direct influence on the machine functionality and is so important for the performance and outcome of the performance.

At the time of drilling, every kind of material has its own rotational speed and it changes based on drill size too. In the scenario of pump installations, there will be a change in the throughput rate and so a conveyor belt needs to be in sync with the functional speed of the device.

These factors come are either directly or indirectly dependent on the speed of the motor. Because of this, one should consider DC motor speed and observe various types of speed control methods. DC Motor speed control is done either done manually by the worker or by using any automatic controlling tool. This seems to be in contrast to speed limitation where there has to be speed regulation opposing the natural variation in the speed because of the variation in the shaft load.

From the above figure, the voltage equation of a simple DC motor is. As there are two types of DC motors, here we will clearly discuss the speed controlling methods of both DC series and shunt motors.

This technique is most widely employed where the regulating resistance has a series connection with that of the motor supply. The below picture explains this. It is a cost-effective technique for persistent torque and mainly implemented in driving cranes, trains, and other vehicles. Here, the rheostat will be in both series and shunting connection with the armature. There will be a change in the voltage level which is applied to the armature and this varies by changing the series rheostat.

Whereas the change in excitation current takes place by changing the shunt rheostat. This technique of controlling speed in DC motor is not so costly because of significant power losses in speed regulation resistances.

The speed can be regulated to some extent but not above the normal level of speed. The speed of a DC series motor can also be done through power supply to the motor using an individual varied supply voltage, but this approach is costly and not extensively implemented. This technique makes use of a diverter.

The flux rate which is across the field can be decreased by shunting some part of the motor current across the series field. The lesser is the resistance of the diverter, the field current is less. This technique is utilized for more than the normal range of speeds and is implemented across electric drives where the speed increases when there is a decrease in load. Here also, with the reduction of flux, the speed will be increased and it is accomplished by reducing the field winding turns from where the flow of current takes place.

In this method, the magnetic flux due to the field windings is varied in order to vary the speed of the motor. As the magnetic flux depends on the current flowing through the field winding, it can be varied by varying the current through the field winding. This can be achieved by using a variable resistor in a series with the field winding resistor. Initially, when the variable resistor is kept at its minimum position, the rated current flows through the field winding due to a rated supply voltage, and as a result, the speed is kept normal.

When the resistance is increased gradually, the current through the field winding decreases. This in turn decreases the flux produced. Thus, the speed of the motor increases beyond its normal value. With this method, the speed of the DC motor can be controlled by controlling the armature resistance to control the voltage drop across the armature. This method also uses a variable resistor in series with the armature.

When the variable resistor reaches its minimum value, the armature resistance is at a normal one, and therefore, the armature voltage drops. When the resistance value is gradually increased, the voltage across the armature decreases. This in turn leads to a decrease in the speed of the motor. The Ward Leonard technique of DC motor speed control circuit is shown as follows:. In the above picture, M is the main motor where its speed is to be regulated and G corresponds to an individually excited DC generator where this is driven by using a three-phase motor and it may be of either synchronous or induction motor.

The generator voltage is varied by altering the field current of the generator. This voltage level when provided to the armature section of the DC motor and then M is varied. In order to keep the flux of the motor field constant, the motor field current has to be maintained as constant.

When the motor speed is regulated, then the armature current for the motor is to be the same as that of the rated level. As the speed regulation corresponds to the rated current and with the persistent field flux of the motor and the field flux till when the rated speed is achieved. And as the power is the product of speed and torque and it has a direct proportion to the speed. With this, when there is an increment in power, the speed increases.

Both the above-mentioned methods cannot provide speed control in the desirable range. Moreover, the flux control method can affect commutation, whereas the armature control method involves huge power loss due to its usage of a resistor in series with the armature.

Therefore, a different method is often desirable — the one that controls the supply voltage to control the motor speed. Consequently, with the Ward Leonard technique, the adjustable power drive and the constant value of torque are acquired from the speed level minimal to the level of the base speed. The field flux regulation technique is mainly employed when the speed level is more than that of the base speed.

Here, in the functionality, the armature current is kept at a constant level at the specified value and the voltage value of the generator is maintained at constant. In such a method, the field winding receives a fixed voltage, and the armature gets a variable voltage. One such technique of voltage control method involves the use of a switchgear mechanism to provide a variable voltage to the armature, and the other one uses an AC motor-driven Generator to provide variable voltage to the armature the Ward-Leonard System.

And the application of the Ward Leonard method is smooth controlling of speed in the DC motor. A few of the examples are mine hoists, paper mills, lifts, rolling mills, and cranes. Apart from these two techniques, the most widely used technique is the speed control of dc motor using PWM to achieve speed control of a DC motor.

PWM involves the application of varying width pulses to the motor driver to control the voltage applied to the motor. The above block diagram represents a simple electric motor speed controller. As depicted in the above block diagram, a microcontroller is used to feed PWM signals to the motor driver.

PWM is achieved by varying the pulses applied to the enable pin of the motor driver IC to control the applied voltage of the motor. The variation of pulses is done by the microcontroller, with the input signal from the pushbuttons. Here, two pushbuttons are provided, each for decreasing and increasing the duty cycle of pulses. So, this article has given a detailed explanation of various techniques of DC motor speed control and how speed control is most important to be observed.

It is furthermore recommended to know about the 12v dc motor speed controller. What is DC Motor? Share This Post: Facebook.

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