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Can a larger VFD be used on a smaller motor?
An oversized VFD can be used for a smaller HP motor. The advantage of this application is that if the motor requirements increase, the VFD may be large enough to still handle the increased load.
Should I oversize VFD?
Altitude also influences VFD sizing, because VFDs are air-cooled. Air thins at high altitudes, which decreases its cooling properties. Most VFDs are designed to operate at 100% capacity up to an altitude of 1,000 meters; beyond that, the drive must be de-rated or oversized.
How much can you overspeed a motor with a VFD?
Motors generally have to withstand 10 % overspeed. But it in no way means many motors cannot withstand much higher over speeds.
Can any motor be used with a VFD?
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.
What size VFD do I need?
Thus, the rule of thumb for sizing the single phase input on a three-phase drive is to use a VFD rated for 2 times the FLA of the motor. For example if your motor is a 10 HP motor with a FLA of 28 amps, then you would need to select a VFD with an amp rating of 56 amps which ends up being around 20 HP.
Can a motor damage a VFD?
Even if you use a “VFD-rated” motor as defined by NEMA MG1 part 31, the motor is still unprotected from shaft currents created by VFDs. These arcs destructively cause pitting, frosting and fluting in motor bearings and bearing races, resulting in premature motor failure.
Can you lose more than 40 hp on a VFD?
Depending on the machine frame size your losses may actually be less than the 40 HP. But as noted, make sure you have your protection and motor parameters set correctly or you could cook your motor.
What should the VFD know about the motor?
The motor data is not just amps but the electrical properties of the motor, motor constants. The VFD should have parameters where you let the VFD know the size of the motor, number of poles and nameplate voltage. The VFD will probably have a stored set of motor constants for each that it will load to get close to optimum efficiency.
Is it OK to use an oversized VFD?
It has no issues using an oversized VFD. Assuming that’s a voltage source drive (most common topology). This design manages the voltage and frequency to attain commanded speed. The current supplied to motor is only what is needed to magnetize the windings plus the torque producing current.
What to look for when setting up a VFD?
When setting up any VFD application use the motor nameplate data to provide an accurate look at what is happening with the load and providing suitable motor circuit protection. Drives are a current delivering device and are marked by horsepower for convenience only.