Method and circuit arrangement for the feedback of commutation energy in three-phase current drive systems with a current intermediate circuit converter

There is disclosed a method and a circuit arrangement for the feedback of commutation energy in three-phase current drive systems with a current intermediate circuit converter. Commutation energy is released at each commutation in the inverter. The commutation unit ensures that the released energy is directly fed back to the current intermediate circuit in two steps. In the first step, the commutation energy is fed into the commutation capacitor by a rectifier circuit (diode bridge and three triacs). In the second step, the commutation energy is fed directly from the commutation capacitor into the current intermediate circuit by means of three semiconductors (first RIGBT, second RIGBT, diode) so that the current of the intermediate circuit flows through the capacitor over a controlled period of time.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. §371 National Phase conversion of PCT/CH2006/000565, filed Oct. 6, 2006, the disclosure of which is incorporated herein by reference. The PCT International Application was published in the German language.

FIELD OF THE INVENTION

The invention relates to a method and a circuit arrangement for the feedback of the commutation energy in three-phase motor drive systems with a current intermediate circuit converter.

BACKGROUND OF THE INVENTION

In a phase sequence inverter, the commutation capacitors are adapted to the leakage inductance of the motor being used. It is therefore very problematic to use a phase sequence inverter for driving different motors having different leakage inductances.

SUMMARY OF THE INVENTION

It is an object of the present invention to eliminate this disadvantage by a cost-effective solution.

According to a first aspect of the invention the object is achieved by a method, wherein in a first step the created commutation energy is stored in a commutation capacitor. In a second step the commutation energy is directly fed from the commutation capacitor to the current intermediate circuit.

The commutation energy is temporarily stored, preferably in an intermediate circuit inductor, and in the following commutation in the inverter, this energy swings back into the commutation capacitor (reactive commutation power).

According to a second aspect of the invention the object is achieved by a circuit arrangement that comprises a commutation capacitor for storing the commutation energy created during an inverter commutation. For feeding the stored commutation energy into the current intermediate circuit the circuit arrangement further comprises two controllable semiconductors and a diode connected in series in the current intermediate circuit.

The invention is advantageously applicable in three-phase motor drive systems where energy feedback to the mains and/or a simple, sensorless positioning by means of synchronous motors is desired. Elevator technology is a typical field of application of such drive systems.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2shows a typical circuit for implementing the method described in claim1.

The depicted RIGBT components,4and5symbolize a reverse blocking component that is switchable on and off by the gate electrode. According to the state of the art, this component is eithera reverse blocking IGBT (RIGBT) oran IGBT with a series connected diode, ora GTO thyristor.
Structure of the Circuit According toFIG. 2:
Current Source1and Inverter2:

Current source1is formed by a line-commutated rectifier connected to the AC network together with intermediate circuit inductor12. Positive power source terminal P1is connected to positive inverter terminal P2, and three-phase motor11is connected to the outputs on the motor side of inverter2. The inverter2comprises no commutation capacitors.

The three motor side outputs of inverter2are connected to the three middle connections of diode bridge10by respective triac components7,8,9.

The common cathode of the three upper diodes of diode bridge10is connected to the positive terminal of the commutation capacitor3, the common anode of the three lower diodes of diode bridge10is connected to the negative terminal of the commutation capacitor3. The positive terminal of the commutation capacitor3is connected to the collector of the first RIGBT4, its negative terminal is connected to the emitter of the second RIGBT5, the emitter of the first RIGBT4is connected to the cathode of diode6, and the collector of the second RIGBT5is connected to the anode of diode6; diode6is connected in series with the negative conductor line, the cathode is connected to the negative current source terminal N1and the anode is connected to the negative inverter terminal N2.

Operation of the Circuit According toFIG. 2:

FIGS. 4ato4eshow the different phases of a complete inverter commutation.

FIG. 4ashows the conditions prior to the commutation. The current is flowing through motor phases a and b.

The inverter commutation is initiated by the simultaneous switch-on of RIGBT26, switch-off of RIGBT25, ignition of triac8and triac9.

According toFIG. 4b, the current is now flowing through commutation capacitor3, which stores the commutation energy.

The current in motor phase b is decreasing and the current in motor phase c is increasing. Commutation capacitor3is being charged. The process is terminated by diodes32and36as well as triac8and triac9as soon as the current in motor phase b reaches zero. The commutation energy is now stored in commutation capacitor3(FIG. 4c).

RIGBT4and RIGBT5are simultaneously switched on. The intermediate circuit current is flowing through commutation capacitor3and is discharging it. The intermediate circuit inductor12is taking up the communication energy (FIG. 4d).

When the voltage of commutation capacitor3reaches its initial value, RIGBT4and RIGBT5are simultaneously switched off.

The commutation process between motor phases b and c is completed, the circuit is ready for the following commutation (FIG. 4e).

FIG. 3shows another exemplary embodiment for implementing the method described in claim1.

In this circuit, instead of an RIGBT, thyristor14is used. Thyristor bridge15fulfills the function of the three triacs7,8,9and of diode bridge10.