CS199386B1 - Connexion of frequency converter with asynchronous motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the connection of a frekyence converter with an asynchronous motor with an inverter and a DC intermediate circuit.

The prior art three-phase frequency inverters for asynchronous machines with a current inverter have at least six controlled thyristor valves in the inverter and usually the same number of decoupling diodes and commutating capacitors, the operation of the inverter being highly dependent on the motor load.

The aforementioned drawbacks have no frequency converter with a three-phase asynchronous motor according to the invention, which is based on the inverter connected by its input terminal to one pole of a direct current source, the output terminals of the inverter being connected to a three-phase asynchronous motor. The zero point of the asynchronous motor is connected to the other pole of the DC power supply, with a choke connected in one or both poles of the DC power supply. The inverter consists of three controlled valves - thyristors and three separating diodes. The commutation of the inverter itself is done by commutating capacitors. The frequency inverter is controlled by cyclically switching the controlled valves.

199 586

1SB 381

By using only three controlled valves, three decoupling diodes and three commutating capacitors as power elements for the inverter, a three-phase inverter is obtained for supplying the asynchronous motors with a variable frequency, thereby enabling the asynchronous motor to be frequency-wise, i.e.. also manage economically. This is particularly advantageous for engines of lower power.

When using a zero-diode controlled valve as a direct current source, only four controlled and four uncontrolled valves, a choke, and three commutating capacitors are required for the power frequency circuit for the power circuit.

In the attached drawing, the frequency converter circuit according to the invention is shown, showing a frequency converter with a current inverter whose controlled valves have anodes connected to a node.

The DC power supply 1 supplies the plus pole via the choke 3 to the inverter 6.

The three-phase asynchronous star-connected three-phase asynchronous motor 6 is connected to the output terminals 16, 17, 18 of the inverter 4, the neutral point 19 of which is connected to the minus pole of the DC source 1. The inverter 6 comprises three controlled valves Each controlled valve 7, 8, 9 is connected to the anode of one of the decoupling diodes 10, 11, 12, wherein the decoupling cathodes are output terminals 16, 17, 18 of the inverter 6. The commutating capacitors 13, 15, 15, connected in a delta, are connected to the individual phases of the inverter on the cathode of the controlled valves. The actual / forced / commutation of the inverter £ is effected by switching on the subsequent phase. Controlling the frequency inverter Execute cyclic switching valves £, ^8: the inverter is £ £ £ source of control pulses, voltage and current of an asynchronous motor is effected by controlling the DC power source 1 by the control device as a second DC power source can be used for any of the controllable DC source current. The asynchronous motor can operate in both motor and brake mode. In the braking mode, the polarity of the DC source 1 voltage is reversed, braking by means of the rearrangement.

The present invention can also be used to supply synchronous or reluctance motors when the frequency converter control is used depending on the position of the machine rotor or when the output voltage of the inverter is controlled.

Similarly, frequency inverters can also be used for other three-phase appliances powered by variable frequency.

Claims (3)

1. Connection of a frequency converter with an asynchronous motor with a direct current source, a choke, an inverter with its own commutation by a subsequent phase, characterized in that the inverter (4) is connected with its input terminal (20) to one pole of the direct current source (1). wherein a star-connected three-phase asynchronous motor (6) is connected to the output terminals of the inverter (16, 17, 18) and the zero-point (19) of the asynchronous motor (6) is connected to the second pole of the DC power supply. A choke (3) is connected to one or both poles of the DC source (1). 2. The asynchronous motor frequency converter connection according to claim 1, characterized in that the inverter (4) comprises three controlled valves (7, 8, 9), eg thyristors, connected to a control pulse source (5), wherein the controlled valves /. 7, 8, 9 are connected by their anodes to the input terminal (20) connected to the plus pole of the direct current source (1), where the cathode of each controlled valve (7, 8, 9) is connected to the anode of one diode (10, 11). 12, while the separating diode cathodes are connected to the output terminals (16, 17, 18) of the inverter (4) to which the asynchronous motor (6) is connected, and for the commutation of the controlled valves (7, 8, 9) commutating capacitors (13, 14, 15) connected in a delta or star and connected to the individual phases of the inverter (4) at the connection point of the controlled valve (7, 8, 9) with the separating diode (10, 11, 12). 3. The asynchronous motor frequency converter connection according to claim 1, characterized in that the controlled inverters (7, 8, 9) of the inverter (4) are connected with their cathodes to an input terminal (20) connected to the minus pole of the direct current source. and wherein the anode of each controlled valve (7, 8, 9) is connected to the cathode of one separation diode (10, 11, 12), while the anode of the separation diode (10, 11, 12) is connected to the output terminals (16, 17). 18 / inverters / 4 /.