From outlet to motor

From outlet to motor From outlet to motor

Besides ancillary resolver and encoder feedback devices, tachometers, sensors downtown and relays, drive systems have four major power parts: source power, VSD, cable and motor. Local electric companies provide source power. It may go through transformers that increase or lower voltage, but its frequency remains a constant 60 Hz.

Power processed by traditional VSDs goes from AC to DC, then into a shaped AC form. Drives reshape power that goes in to control motor startup, operating speed and stopping. Prior to turning the motor at a set speed, source power must be converted from AC to DC by means of a rectifier. This AC-to-DC conversion is necessary before the power can be shaped into a variable frequency signal. A diode is used for simple rectifying or silicone controlled rectifiers (SCRs) are used for more intelligent rectification. Rectifiers convert incoming 60 Hz AC to DC, and multiply that voltage by 1414 — so 460 V a.c. becomes 650 V d.c.

The next component that power encounters on its journey to the motor is a large capacitor, known as the DC bus. Capacitors store energy, and DC buses act like batteries to hold and then flush energy out (as DC power) to the next part of the drive, the inverter. Inverters convert DC back to AC with an electronic component known as a bipolar transistor. The inverter is controlled to vary output frequency so that the motor receives the correct downtown flow of power pulses. Insulated gate bipolar transistors (IGBTs) are one of the fastest-switching inverters in pulse width modulation (PWM)-type VSDs.