# Quick Answer: How Do You Control A VFD?

## How do I know if a motor is VFD rated?

Three major factors should be considered when determining if a motor is compatible with a VFD: the motor winding insulation, motor bearings and pump operating speed range..

## How is a VFD controlled?

c. A variable frequency drive controls the speed of an AC motor by varying the frequency supplied to the motor. … This section of the VFD is often referred to as the DC link. This DC voltage is then converted back into AC.

## How does a VFD slow down a motor?

They control motor speed using pulse width modulation, whereby waveform alteration rather than voltage adjustment is used to slow down or even speed up off-the-shelf induction motors relative to nameplate values, provided shaft bearings and cooling are up to the task.

## What is the difference between scalar control and vector control?

The scalar control method is based on varying two parameters simultaneously. This speed can be varied by increasing or decreasing the supply frequency, though this results in a change of impedances. … With vector-based control, you can achieve tighter speed control, higher starting torque, and higher low-speed torque.

## What is Torque in VFD?

The Y axis is the percent of HP and torque. HP and torque are both 100 percent at 60 hertz (base motor speed). When the VFD reduces frequency and motor speed, it also reduces voltage to keep the volts/hertz ratio constant. Torque remains at 100 percent, but HP is reduced in direct proportion to the change in speed.

## Can you run a VFD without a motor?

Well, you can program the VFD without actually connecting it at output, just give the rated voltage at the input terminals and start programming. Most VFDs you can even ‘run’ with no load connected, especially if running open loop V/Hz mode.

## Can you run a VFD over 60hz?

Good design dictates that a system should never be designed with the intention of running a motor at greater than 60hz. Because good design does not always exist, we have the capability of running our drives at greater than 60hz. An AC motor is designed to provide a given amount of torque at a given voltage and speed.

## What is vector control in VFD?

Vector control, also called field-oriented control (FOC), is a variable-frequency drive (VFD) control method in which the stator currents of a three-phase AC electric motor are identified as two orthogonal components that can be visualized with a vector. … FOC is used to control AC synchronous and induction motors.

## How slow can you run a motor on a VFD?

Any VFD is capable of telling a motor to run at 1Hz or 1/2Hz or 0.01Hz, but that does not mean the motor will do that without damage. So there are different DESIGNS of motors available, and those that are designed for operation on a VFD are called “inverter duty” (or something to that effect).

## Can a VFD increase motor speed?

VFDs can be used to control AC motor speeds by changing the motor’s frequency without sacrificing the output power of the motor. This is done by turning the speed pot (explained in section three) of an AC motor drive. Visit the blog “What’s Your Frequency” for additional information regarding motor frequencies.

## How many types of VFD are there?

twoThere are two major types of variable frequency drive on the market: mechanical and electrical.

## Can a VFD damage a motor?

Shaft currents induced by VFDs can lead to motor failures. Without some form of mitigation, shaft currents travel to ground through bearings, causing pitting, fusion craters, fluting, excessive bearing noise, eventual bearing failure, and subsequent motor failure. This is not a small problem.

## What can cause a VFD to fail?

Many faults are caused by misapplication of the VFD. Process changes, such as variations in load or speed; power issues, such as capacity switching by the utility; or changes in environmental operating conditions are not immediately obvious, but could be a major contributor to VFD failure.

## How do you control frequency in VFD?

VFDs manipulate the frequency of their output by rectifying an incoming AC current into DC, and then using voltage pulse-width modulation to recreate an AC current and voltage output waveform. However, this frequency conversion process causes 2% to 3% loss as heat in the VFD — caloric energy that must be dissipated.