Variable Frequency Drives On People's Contributions
Variable Frequency Drives should be seriously considered when replacing motors or updating outdated equipment. A Variable Frequency Drive (VFD) controls the speed of a motor, specifically a three phase motor. Since motor-driven centrifugal pumps, fans, and blowers run at extended periods of time at high speeds, even slight reductions of speed can result significant energy savings. Without a VFD, motors run at higher speeds continuously, which can lead to excessive and unnecessary wear on motors and pumps.
When the power is on and applied to the inverter, you can access the “U” parameters. The “U” parameters are the monitor parameters that allow the user to see what is happening. It could pull too much voltage off the DC Bus too quickly and cause a Uv (Under Voltage) fault. Viewing the “U” parameter that monitors the DC Bus voltage you will see the DC Bus has approximately 340 Volts on it for a 230V hoist. With an UP run button press you will note the voltage drops significantly at the first button press. With too quick of a ramp-up time, the voltage will drop even more causing an Under Voltage.
The VFD changes the frequency to the electric motor to match output needs, allowing motors to run at slower speeds when demands are lower, resulting in less energy used. Running motors at slower speeds when demands are lower has several benefits.
Across-the-line single-speed systems start motors abruptly, subjecting the motor to a high starting torque and to current surges that are up to 8 times the full-load current. Variable speed drives instead gradually ramp the motor up to operating speed to lessen mechanical and electrical stress, reducing maintenance and repair costs, and extending the life of the motor and the driven equipment. Typically, startup will be less than 2 Hz, then ramp up to its normal operating frequency; eliminating the need for a soft starter. Stopping the motor works the same, slowly ramping the frequency down to 0 Hz. An additional advantage to slower running speeds is the reduced wear on the pump and blower bearings, and electric motor bushings. The result is less maintenance costs, fewer parts replaced, and reduced labor in repairing and replacing these components. Another advantage eliminates the need for valves and dampers to control output since the output is controlled by the speed of the motor. Valves and dampers can cause damaging backpressures that are eliminated with the VFD. For more information about variable frequency drives please the website of invt.
Related Reading: Frequency Inverter