ELECTRIC MOTOR – VARIABLE FREQUENCY DRIVES COMPATIBILITY.
VFD compatibility with motors is complex. As a result, many variables must be considered when determining the suitability of a particular motor for use with a VFD.
Selecting a suitable Variable Frequency Drive for an electric motor does not lie on horsepower alone. There are other factors that determines Electric Motor – VFD compatibility.
Let’s take a look at some of those factors to consider when choosing a VFD for your Electric Motor.
FULL LOAD AMPERAGE (FLA)
Can your AC Drive handle the motor’s electric current demands?
Every electric motor has a full load current requirement – which is found on the motor nameplate – that is the first step to determine VFD – Electric motor compatibility.
If you are feeding the drive with single – phase power, be sure to use the drive ratings for single – phase. Variable frequency drives are derated significantly for single – phase operation.
Always remember that all AC Motors with VFDs must be three-phased. VFDs always create a three-phase output of the motor, even when the drive is powered in a single–phase power.
As altitude increases, air becomes less dense. The decrease in density of air reduces the cooling properties of the air. If the VFD is at a high altitude, the drive must be oversized to compensate for the decrease in cooling.
Drives produces a notable amount of heat and could lead to the internal temperature of an enclosure to surpass the temperature rating of the VFD.
Can the drive handle overload conditions during startup?
The VFD may need to be upsized until an adequate one that can handle the load is gotten. Most AC Drives are designed to operate at 150% overload for 60seconds. Most applications experience temporary overload due to starting conditions or impact loading.
If the application requires an overload greater than 150% or longer than 60seconds, it means such drive needs to be oversized.
There are two types of application; they are Variable Torque (VT) and Constant Torque (CT) and each has different ratings.
VT ratings are used for pumps and fans while CT ratings are used for conveyors and general machine control. You are required to ascertain the application type because the drive specifications are organized accordingly. But CT is the recommended rating when you uncertain of the application type.
Default carrier frequency can do a good job, but to reduce audible noise, heat dissipation or power consumption, the carrier frequency for the drive has to be modified.