The Variable Frequency Drive is a particular kind of adjustable-speed drive that is used to control the speed of an AC motor. In order to control the motor’s rotational speed, a Variable Frequency Drive controls the frequency of the electrical power supplied to it.
How is the speed of an AC motor controlled?
AC Motor Control Basics
The AC motor receives power, which is converted by the AC motor controller into an adjustable frequency. This adjustable output allows the motor speed to be precisely controlled.
How does a variable speed AC motor work?
Variable speed drives supply specific amperage and voltage to a motor. If the supply power is in AC form, VSDs utilize a rectifier circuit to convert the AC to DC at a specified voltage and amperage that the drive can adjust. Changing the voltage of the DC changes the speed of the motor.
How do you slow down an AC motor?
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.
How do you increase motor speed?
Increasing the speed can be achieved by increasing the supply frequency as the speed and frequency are directly proportional; however, there are two constraints. The first is the saturation of the magnetic circuit, but this issue can be significantly avoided by keeping the V/f ratio constant.
Can you speed control a PSC motor?
The 770-PSC Control offers a way to add existing single phase PSC or shaded pole motor fans to a building automation system. The 770-PSC control measures the motor’s RPM, using an easy to attach sensor, and can adjust the motor’s speed to match a chosen set point.
Does voltage affect AC motor speed?
AC Induction Motor Speeds
AC motors are unique because they are built to run at specific speeds regardless of their design or manufacturer. The speed of an AC motor is dependent on the number of poles it has and the line frequency of the power supply, not on it’s voltage.
How do you reduce voltage in a motor?
A simple and common method of starting a motor at reduced voltage is used in primary resistor-type starters. In this method, a resistor is connected in series in the lines to the motor. As current flows through the resistors, a voltage drop occurs, and the voltage at the motor terminals is reduced by that amount.
What type of motor is variable speed?
Variable frequency drives or alternating current (AC) motor adjustable speed drives. They are used in synchronous motors and both in wound-rotor and in squirrel-cage rotor asynchronous induction motors.
Which motor is used for variable speed?
For applications where variable speeds are necessary, typically an AC motor with an Inverter or brush motors are used. Brushless DC motors are an advanced option due to their wide speed range, low heat and maintenance-free operation. Stepper Motors offer high torque and smooth low speed operation.
Can you put a variable speed control on any motor?
To have electronically variable speed you will either need a universal/dc motor with PWM speed controller or a 3-phase inverter-duty induction motor with a variable-frequency inverter to control its speed.