Frequency converter and drive for electric motor
First Claim
1. A frequency converter, comprisinga network inverter to be connected to a multiphase alternating voltage supply,a capacitor battery of a direct voltage intermediate circuit, a second inverter to be connected to a load,a switch means that transfers power bidirectionally and is connected between the multiphase alternating-voltage supply and the network inverter and configured to disconnect the power supply from the network inverter until the voltage of the capacitor battery reaches a predetermined level,a first, second and third semiconductor switch connected to between a first, second and third phase, respectively, of the multiphase alternating voltage supply and said capacitor battery and configured to first operate in a current regulating mode for charging the capacitor battery with regulated charging current until the voltage of the capacitor battery reaches a predetermined level, and to operate then in a diode bridge mode in parallel with the network inverter.
1 Assignment
0 Petitions
Accused Products
Abstract
A charging contactor and charging resistor of a capacitor battery in a prior art intermediate circuit of a frequency converter are replaced with three semiconductor switches connected between a three-phase voltage supply and a capacitor battery. When the frequency converter is connected to a supply network, the three semiconductor switches are arranged to operate at first in a current regulating mode in order to charge the capacitor battery using a regulated charging current until the voltage of the capacitor battery reaches a predetermined level. After this, the three semiconductor switches are directed to operate in a diode bridge mode in parallel with an actual network inverter, thus providing a second rectification branch. In a preferred embodiment of the invention, each semiconductor switch comprises a diode and a series connection of a gate-triggered component, preferably a thyristor.
11 Citations
13 Claims
-
1. A frequency converter, comprising
a network inverter to be connected to a multiphase alternating voltage supply, a capacitor battery of a direct voltage intermediate circuit, a second inverter to be connected to a load, a switch means that transfers power bidirectionally and is connected between the multiphase alternating-voltage supply and the network inverter and configured to disconnect the power supply from the network inverter until the voltage of the capacitor battery reaches a predetermined level, a first, second and third semiconductor switch connected to between a first, second and third phase, respectively, of the multiphase alternating voltage supply and said capacitor battery and configured to first operate in a current regulating mode for charging the capacitor battery with regulated charging current until the voltage of the capacitor battery reaches a predetermined level, and to operate then in a diode bridge mode in parallel with the network inverter.
-
12. An electric motor drive comprising a frequency converter, said frequency converter further comprising
a network inverter to be connected to a multiphase alternating voltage supply, a capacitor battery of a direct voltage intermediate circuit, a second inverter to be connected to a load, a switch means that transfers power bidirectionally and is connected between the multiphase alternating-voltage supply and the network inverter and configured to disconnect the power supply from the network inverter until the voltage of the capacitor battery reaches a predetermined level, a first, second and third semiconductor switch connected to between a first, second and third phase, respectively, of the multiphase alternating voltage supply and said capacitor battery and configured to first operate in a current regulating mode for charging the capacitor battery with regulated charging current until the voltage of the capacitor battery reaches a predetermined level, and to operate then in a diode bridge mode in parallel with the network inverter.
-
13. An electric motor drive comprising n frequency converters in parallel such that each frequency converter is connected to a dedicated 6-phase alternating voltage supply, wherein n=2, 3, 4, . . . , each said frequency converter further comprising
a network inverter to be connected to a multiphase alternating voltage supply, a capacitor battery of a direct voltage intermediate circuit, a second inverter to be connected to a load, a switch means that transfers power bidirectionally and is connected between the multiphase alternating-voltage supply and the network inverter and configured to disconnect the power supply from the network inverter until the voltage of the capacitor battery reaches a predetermined level, a first, second and third semiconductor switch connected to between a first, second and third phase, respectively, of the multiphase alternating voltage supply and said capacitor battery and configured to first operate in a current regulating mode for charging the capacitor battery with regulated charging current until the voltage of the capacitor battery reaches a predetermined level, and to operate then in a diode bridge mode in parallel with the network inverter.
Specification