## Why does cable length between VFDs and motors matter?

If such a signal encounters the motor terminals while the impedance of the power cord and the motor are not consistent (which is the case when the power cord is too long) the voltage reflectance may occur during this time.

## What is the range of a VFD?

VFDs can provide voltage to motors at frequencies of from < 1 Hz to approximately 120 Hz. Currently, they are available for motors ranging from 0.33 hp to thousands of horsepower. Operating a motor at other than the rated frequency and voltage affects motor current and torque.

Where do you mount a VFD?

VFD installation considerations The variable frequency drive must be mounted on a vibration free vertical surface, away from heat radiating sources. Do not mount the variable frequency drive in direct sunlight or on a hot surface.

Components Used Maximum Motor Lead Length
Reactor near the VFD’s output ~300 ft (90 meters)
Reactor near the motor’s input Consult reactor manufacturer
dV/dT Filter near the VFD’s output ~1000 ft (600 meters)
Sine Wave Filter near the VFD’s output >1000 ft (600 meters)

### What happens as the length of conductors increases and or the motor drive output carrier frequency increases?

As the length of conductors increases and/or an electric motor drive’s output carrier frequency increases, the voltage spikes become larger.

### What is the maximum frequency of VFD?

With the use of Variable Frequency Drives (VFD), motors can be run at higher than 60 Hz, known as an overspeed condition, typically as direct drive fan wall/plenum fans (per NIH DRM 6.2. 4.2, the maximum operating speed is 90 Hz).

What is the minimum RPM of a motor?

(Base speed = 2500 RPM)

Minimum Speed (RPM) % Motor Base Speed Speed Range Ratio
3750 150 1.5:1
5000 200 2:1
7500 300 3:1

How do you fit a VFD?

How to Wire a VFD

1. STEP 1: Make sure everything is correctly sized and accounted for.
2. STEP 2: Make sure you have a properly-sized circuit breaker rated for your amps and VFD.
3. STEP 3: Run Wires – (3) power wires and (1) ground wire from your breaker panel to your VFD.
4. STEP 4: Run wires from VFD to motor.

## When should you not use a VFD?

Does every motor need a drive? When NOT to use a VFD

1. This motor’s load is fixed and unrestricted.
2. You need this motor to operate at very low or very high speeds.
3. You’re planning to install this drive on a motor that is more than 15 years old.
4. You have power quality issues.