DE594372C - Starting procedure for asynchronous machines excited by three-phase machines - Google Patents

Description

GERMAN EMPIRE

ISSUED ON
MARCH 16, 1934

REICH PATENT OFFICE

PATENT LETTERING

CLASS 21 d ² GROUP 27 m

Patented in the German Empire on March 2, 1929

Large asynchronous machines, namely generators and phase shifters, are sometimes not, as is usually the case, through resistances, but with the help of Anwuri motors left on. This allows the secondary circuit to be dimensioned for low currents without affecting the resulting having to take into account the high standstill voltage of the rotor winding.

But if the asynchronous machine after it has been driven by the starter motor on approximately synchronous speed was brought, connected to the mains, so occur extraordinarily high currents in the stator and rotor of the asynchronous machine, since the short-circuited rotor winding every fast Seeks to throttle down the field change. By using pre-contact resistors when switching on and by additional Resistance in front of the runner has tried to mitigate this disadvantage. Can be eliminated but it will not become with these means that make the investment more expensive.

You also have to start asynchronous generators Choke coils connected between the mains and the generator. This allows you to do so at the moment of switching on the occurring current surge can be mitigated somewhat, but not prevented.

When starting synchronous machines, you already have the reactive current before the Shorting the choke coil made zero by energizing the inductor. This known arrangement has, but apart from the fact that this is the Starting synchronous machines has the disadvantage that the active current when Power on cannot be scaled down. It must therefore be the deviation when switching on be relatively small from the synchronous speed, so that the starting motor can be sized relatively large got to.

The invention avoids all these disadvantages of the previously known arrangements in that that when starting with three-phase machines .Asynchronous machines that after starting up by starting motors or prime movers via choke coils the mains are laid, first the stator winding of the asynchronous machine in series with the choke coil is connected to the mains, while in the circuit the one with the Three-phase exciter in series-connected rotor winding of the asynchronous machine Additional resistors are switched on, whereupon the additional resistors are short-circuited the reactive current through gradual excitation of the three-phase exciter in the stator winding of the asynchronous machine is suppressed and finally the almost dead Choke coil is short-circuited.

*) The patent seeker stated as the inventor:

Dipl.-Ing. Wilhelm Weiler in Berlin-Niederschönhausen.

The invention is shown in the drawing in an embodiment illustrated.

In the figure, a means the asynchronous machine, m the starting motor, which has the same number of poles as the machine ο, k the three-phase collector machine with compensation winding and rotor excitation, which can also be replaced by one with stator excitation, d the starting choke coil and t the controllable excitation transformer.

The choke coil d is dimensioned for approximately half the line voltage and half the magnetizing current of the asynchronous machine a. The machine α, if it were connected to the mains at exactly synchronous speed via the choke coil, would absorb about half the normal magnetizing current that is required for half the mains voltage, since half of the mains voltage is throttled in the choke coil. Now, however, the highest speed reached after short-circuiting the starting resistor of the starter motor m differs proportionally

² S strongly depends on the synchronous speed, since the machine m is small compared to the machine a . It is therefore ensured by installing the resistor r ₂ in the secondary circuit of the asynchronous machine α that the active current absorbed when the machine α is switched on is sufficient to accelerate the asynchronous machine fast enough to almost synchronous speed, but still so small compared to half the normal speed Magnetism sierungsstrom is that the throttled in the choke coil d voltage is almost in phase with the line voltage, so that only about half the line voltage remains for the asynchronous machine.

The starting process takes place as follows:

After all switches have been opened

are and the excitation transformer t has been set to the voltage zero, the switch J _{0 is} closed, the starting resistance of the starting motor m is gradually reduced and finally short-circuited. Then the asynchronous machine α is connected to the network by closing the switch J ₁ and a short time afterwards (one to two seconds later) the resistor r ₂ is short-circuited by the switch J _2. The asynchronous machine α now runs practically synchronously. Now the three-phase collector machine k is gradually excited by the transformer t in such a way that the asynchronous machine α is excited from the rotor. This reduces the reactive component from «Ι to zero. The choke d is almost dead, and the asynchronous machine α receives the full line voltage. The choke coil d is now short-circuited by the switch J ₃ and the switch J _{0 is} opened.

Claims (1)

Claim: Starting method for asynchronous machines excited by three-phase machines, which are placed on the busbars via choke coils after start-up by starting motors or prime movers, characterized in that first the stator winding of the asynchronous machine is connected to the network in series with a choke coil (d) , while in the circuit the with the three-phase exciter machine connected in series rotor winding of the asynchronous machine Züsatzwiderstände (r ₂₎ are switched on, whereupon the additional resistors (r ₂₎ are short-circuited, the reactive current suppressed by gradual energization of the three-phase exciter machine in the stator winding of the asynchronous machine and finally the nearly tensionless inductor (d) is short-circuited. 1 sheet of drawings