VARIABLE FREQUENCY DRIVE CIRCUIT WITH OVERVOLTAGE PROTECTION

摘要

A variable frequency drive (VFD) circuit includes an input connectable to an AC source, a rectifier to convert an AC power input to a DC power, a DC link to receive DC power from the rectifier and having a DC link voltage thereon, a DC link capacitor bank with one or more capacitors connected to the DC link, and a pre-charge circuit coupled to the DC link capacitor. The pre-charge circuit further includes one or more resistors, one or more pre-charge relays each operable in on and off states to selectively control a current flow through the resistor(s) so as to control an initial pre-charge of the DC link capacitor, and an overvoltage relay operable in on and off states to selectively cut-off a current flow to the DC link capacitor bank, so as to prevent an overvoltage condition in the DC link capacitor bank.

主权项

1. A variable frequency drive (VFD) circuit comprising:
an input connectable to an AC source; a rectifier connected to the input to convert an AC power input to a DC power; a DC link coupled to the rectifier to receive the DC power therefrom, the DC link having a DC link voltage thereon; a DC link capacitor bank comprising one or more capacitors connected to the DC link to smooth the DC link voltage; and a pre-charge circuit coupled to the DC link capacitor bank, the pre-charge circuit comprising:
one or more resistors;one or more pre-charge relays each operable in an on and off state to selectively control a current flow through the one or more resistors, so as to control an initial pre-charge of the DC link capacitor; andan overvoltage relay operable in an on and off state to selectively cut-off a current flow to the DC link capacitor bank, so as to prevent an overvoltage condition in the DC link capacitor bank.