Variable Frequency Drives - Automate Your Spindle


When selecting a VFD remember

As VFD's have increased in popularity, drive manufacturers have spent considerable time and effort to incorporate new technologies into their drives. Features like programmable acceleration and deceleration ramps, speed presets, diagnostic abilities, plug-in programming modules, and off-line programming tools are now available. Operator interfaces have also been improved with some drives even displaying information in words and phrases rather than numeric codes, to aid in setup and general day-to-day operation.


The current required for a motor to provide the needed output is the basis for selecting the proper size drive. Horsepower ratings, while listed by most drive manufacturers as a guide to the maximum motor size under most applications, are less precise. As a rule, VFD's have an overload current capacity of approximately 150% for one minute, based on nominal output. If an application exceeds these limits, a larger drive should be selected.

Power Supply

Drives will typically tolerate line-voltage fluctuations of 10-15% before tripping. Some drives have a "ride through" capacity of a second or two before a fault is triggered, shutting down the drive. Drives can be programmed for multiple automatic restart attempts although manual restarts may be preferred for safety reasons.


The most critical application factor, motor torque must be considered carefully prior to selecting a VFD. Determining whether the application will require variable torque or constant torque is key, as the available torque may decrease as motor RPM's decrease.

Environmental Factors

Heat, moisture, vibration, and dirt are all enemies of variable frequency drives and should be minimized. Rated for operation in specific ambient temperature ranges, VFD's should be heated or cooled depending on the environment to obtain maximum efficiency and drive life.

Dynomax has the experience and expertise to match your precision spindle with the perfect VFD for your application. All the benefits with none of the headache, just another way Dynomax helps you do more.