Can any motor be variable speed?
Variable speed operation is obtained by varying the effective resistance in the rotor circuit. Ac synchronous motor with brushless ac or brushed excitation. Ac synchronous motor with permanent magnet excitation: This type of motor is specifically designed for operation with a variable frequency drive.
Can DC motors be variable speed?
A: In general if you don’t do anything special to it, a DC motor will have variable speed. The main factors are the DC voltage applied to the armature coil and the amount of torque load you are trying to drive. In order to make it into a constant speed DC motor you have to have some sort of electronic feedback.
Is series motor a variable speed motor?
From speed-current characteristic curve it is obvious that the series motor is a variable speed motor i.e., speed varies with the variation in line current. With the decrease in load on a dc series motor, the speed increases and may become dangerously high at very light loads.
Which are two types of variable speed motors?
There are three general types of variable speed drives- DC Motor drives, Eddy Current Drives, and AC Motor drives. Each type of variable speed drive can be divided into different variations.
Can any motor use VFD?
Summary. While we’ve solved the single-speed problem of AC induction motors by introducing the variable frequency drive, not all motors are VFD compatible. Some motors are specifically designed to run on VFD power, while others need a few components added to the system to be compatible.
Which is better VFD or VSD?
In general, VFDs are more energy efficient and result in more energy saved than VSDs. VFDs can connect to more than one motor. This allows them to control other elements in a system such as a pump system or an HVAC.
What is a variable motor?
Variable Speed Motor
A variable-speed motor is a component of high-performance residential furnaces and air handlers. Connected to fan blades, it moves air through your ductwork and into the different rooms of your home.
How do motors create variable speed?
AC motors are constant speed devices but their speed can vary if you change the input voltage or frequency or the windings that make the motor rotate. The most common and efficient way of changing the speed is to vary the frequency by using an inverter as the power supply.
What is variable speed system?
Variable speed technology refers to the type of compressor in your air conditioner or heat pump. The compressor is the heart of your air conditioning or heat pump system. It creates the cooling capacity for your system. Variable speed compressors allow a unit to run at virtually any speed between 30% and 100%.
Why DC motor has variable speed?
DC Series motor has high rate of acceleration and retardation. DC Series motor is variable speed motor. Due to these characteristics motor is protected against overload. DC Series motor speed-torque characteristics are such that as torque increases speed decreases.
Why DC motor is called variable speed drive?
The most common types rely on the forces produced by magnetic fields. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current flow in part of the motor.
Why a DC motor is used for variable speed applications?
Higher Starting Torque Than AC
Without a load to slow them down, DC motors can burn out quickly. For applications that need constant low-speed or variable-speed torque, DC motors are ideal.
How PWM is used in VFD?
The PWM technique is used in VFD mainly to create a sinusoidal current waveform output to produce torque in the motor. The one transistor on the top portion of the diagram and one at the bottom of the diagram must be activated to flow the current between two phases of the motor.
Where is VFD used?
The most common uses of a VFD are for control of fans, pumps and compressors, and these applications account for 75% of all drives operating globally. Soft starters and across-the-line contactors are other, less sophisticated types of motor controllers.
What are variable speed pumps?
Variable-speed pumps let you control the speed, whether low or high or anywhere in between. Most of these energy-efficient pumps are powered by a different type of motor than the first two, called a permanent magnet motor. This type of motor is used in magnetic resonance imaging (MRI) machines and electric cars.