Can You Oversize A VFD?

How do you protect a VFD?

AC line reactors also protect the VFD from power system surges and can prevent over-voltage trips.

The line reactors have either 3% or 5% impedance.

5% impedance line reactors will provide lower THID and provide better protection than 3% line reactors..

How do I choose a VFD for my motor?

Read below to learn more about the six factors you should be considering when choosing a VFD.Full Load Amperage. The first step in this process is making sure the drive can handle the motors current demands. … Overload. … Application Type. … Altitude. … Temperature. … Carrier Frequency.Feb 26, 2018

How long will a VFD last?

about 7-12 yearsMost manufacturers will admit the typical life expectancy is about 7-12 years … but there are many factors at play. VFD components like fans and capacitors have a finite life and starting at about 5 years, these components can start to fail and will need to be replaced.

How does a VFD vary compressor capacity?

A VFD works by converting the input current to direct current, and, from this, generating a simulated AC signal at varying frequencies. Varying the frequency will vary the motor speed, thus varying the compressor capacity.

Can VFD causing motor vibration?

Circulating bearing currents—related to the use of VFDs—are primarily caused by the speed of the inverter switching in the output stage of a VFD. … Over time, this pitting creates a fluting on the face of the bearing races. When the fluting becomes severe enough, bearings can fail, which causes increased motor vibration.

What is a VFD in HVAC?

A VFD is an electrical device used to control the rotation speed of an alternating current (AC) electric motor by adjusting the frequency of the electrical power supplied to the motor. … Most VFDs used in HVAC applications are inverters using sine-coded PWM technology.

Can I run a 50Hz motor at 100 Hz?

Now, since the motor is rated for 380V 100Hz. For driving it at 50Hz you need to halve the voltage as well i.e, V=190 volts. … You can also keep Voltage below 190V at 50Hz to reduce operating torque but not beyond 190 otherwise the core will undergo saturation.

How does a VFD control motor speed?

A variable frequency drive controls the speed of an AC motor by varying the frequency supplied to the motor. … The first step in this process is to convert the AC supply voltage into DC by the use of a rectifier. DC power contains voltage ripples which are smoothed using filter capacitors.

Are all motors VFD compatible?

Output voltages are available for VFDs to match almost any existing motor voltage. However, very few, if any, VFDs have a direct 13,800-volt output for very high-voltage motors. For these cases, using a step-up transformer on the output of the VFD is often necessary to match the motor voltage.

How does a VFD affect torque?

A VFD cannot increase the voltage above its supply voltage. This causes the current to decrease as frequency increases, thus decreasing the available torque. Theoretically, torque is reduced by the ratio of the base speed divided by the higher speed (60 hertz / 90 hertz = 67%).

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.

Can you run a VFD over 60Hz?

Traditionally, maximum motor speed has been 60Hz for motors controlled by VFDs. Sometimes, it is necessary to have a higher upper frequency limit. Danfoss VFDs can run at output frequencies higher than 60Hz. … The VFD doesn’t care as long as you are below its rated outputs.

What is a VFD rated motor?

VFDs vary the speed of the pump to optimize system control, usually by lowering the speed below the baseline frequency. … As a result, define the pump operating speed range to ensure the motor is not overloaded at increased speed and the motor is able to withstand decreased cooling at lower speeds.

How much can you overspeed a motor with a VFD?

If your load really requires it, depending on the manufacturer, motors rated for use with vector VFD drives can often accommodate 1000:1 or 2000:1 turndown ratios. If you need super-high turndown ratios with high levels of low-speed torque, this will mean using a VFD with vector control.

How far can a VFD be from the motor?

150 feetTo reduce the likelihood of possible excessive voltage overshoot at the motor terminals, the lead length distance between the motor and VFD should be less than 150 feet.

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.

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.

Does a VFD replace a motor starter?

VFD does essentially replace a motor starter in applications where they are used, there still can be control schemes where a contactor may be used to interrupt power – typically only for occasional shut down situations and not as a routine control method – VFD’s don’t play well with contactors in the circuit, total …

What causes a VFD to trip?

In a VFD application, the motor reacts to the varying voltage and frequency from the drive and develops torque for the load. … Eventually the current demands become too large for the VFD to handle, so it trips out on an overcurrent fault. Overcurrent faults are the most common faults that will shut down a drive.