It is not advisable to operate a single motor with a variable frequency drive. While it is technically possible, the disadvantages far outweigh any benefits that you might expect. In a majority of cases, it is less expensive to upgrade to a 3 phase motor for use with a VFD.
How a Variable Frequency Drive Works
VFDs give you control over system performance, monitoring the speed of motors or pumps and adjusting current on demand. The VFD accepts a 3 phase AC input and then outputs the desired AC or DC current. This allows motors to operate efficiently under load variations.
How the VFD Benefits the System
Controlling the motor speed offers many advantages. First, the VFD provides greater efficiency in both power use and transfer rate in a pump or motor. The VFD senses the load on the system and provides power to compensate. It also manages such problems as system malfunctions and overloads. This automatic, intelligent control can extend motor life, prevent system failure, and increase operational output.
Problems with Using a Single Phase Motor
Single phase motors are wound differently than a 3 phase motor. In order to use a single phase motor with a VFD, the motor must be inverter grade, which means paying to have the existing motor rewound, or purchasing a new motor. Even when the motor specifications have been met, you may experience problems with single phase motor operation. This is more commonly noticed at low speeds where the motor is being forced to operate at lower rpm.
Advantages of Upgrading the Motor
Modifying a single phase motor to work with a VFD is not cost-efficient. Rather than expending resources to to make the necessary changes, it is usually better to upgrade to a 3 phase motor. In addition to being less expensive, 3 phase motors are often smaller and lighter. Upgrading means a longer system life, greater output control, and will provide additional benefits such as reducing operating temperatures.
For more than 30 years, Mader Electric has provided installation, training and maintenance on pump motor system up to 4000 horsepower. In addition to being the premiere pump and motor company in the Sarasota area, we also have a state-of-the-art training facility to help our clients get up to speed as soon as the installation is complete. To learn more about our variable frequency drive services, and more contact us today.