1) The number of motor poles
2) The frequency of the applied power.
Inverter Drives - An inverter is an electronic power unit for generating AC power. By using an inverter type AC drive, the speed of a conventional AC motor* can be varied through a wide speed range from zero through the base (60 Hz) speed and above (often to 90 or 120 hertz).
Voltage and Frequency Relationship - When the frequency applied to an induction motor is reduced, the applied voltage must also be reduced to limit the current drawn by the motor at reduced frequencies.(The inductive reactance of an AC magnetic circuit is directly proportional to the frequency according to the formula XL = 2fL. Where: = 3.14, f = frequency in hertz, and L= inductive reactance in Henrys.)
Variable speed AC drives will preserve a continuous volts/hertz partnership from 0 - 60 Hertz. To get a 460 motor this ratio is 7.six volts/Hz. To calculate this ratio divide the motor voltage by 60 Hz. At low frequencies the voltage will probably be low, because the frequency increases the voltage will improve. (Note: this ratio might be varied somewhat to alter the motor overall performance traits such a supplying a low finish increase to enhance beginning torque.)
Depending on the type of AC Drive, the microprocessor control adjusts the output voltage waveform, by one of several methods, to simultaneously change the voltage and frequency to maintain the constant volts/hertz ratio throughout the 0 - 60 Hz range. On most AC variable speed drives the voltage is held constant above the 60 hertz frequency. The diagram below illustrates this voltage/frequency relationship.
Inverter Duty Motors - Initially standard AC motors were employed on inverter drives. Most motor manufacturers now offer Inverter Duty Motors which provide improved performance and reliability when used in Variable Frequency Applications. These special motors have insulation designed to withstand the steep wave front voltage impressed by the VFD waveform, and are redesigned to run smoother and cooler on inverter power supplies.
Sensorless Open and Closed Loop Vector AC Drive. The VFD-B series represents Delta's NEMA1 general purpose AC drive. The VFD-B series drive is rated to provide constant torque, featuring open and closed loop vector control. Delta offers an optional 2000 Hz high speed output that can be factory programmed at the customer's request.
Specifications
Output frequency 0.1 ~ 400 Hz
Adjustable V/f curve and vector control
Master/Auxiliary and 1st / 2nd frequency source selectable
16-step speed control and 15-step preset speed process control
Built-in PID feedback control
Auto torque boost & slip compensation
Built-in MODBUS communication, baud rate up to 38400 bps
Support communication module (DN-02, LN-01, PD-01)
Applications
Air conditioners for large buildings; woodcarving machine; punching machine; wastewater treatment systems; crane drive and swivel; washing machine; vertical stamping machines; compressor; elevator; escalator; circular loom; flat knitting machine; pasta machine; four-sided woodworking planer, etc.
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