Method for starting and stopping an asynchronous motor

Patent metadata

Field	Value
Publication number	US-12081146-B2
Application number	US-202117927438-A
Country	US
Kind code	B2
Filing date	Apr 23, 2021
Priority date	May 25, 2020
Publication date	Sep 3, 2024
Grant date	Sep 3, 2024

Abstract

A method for starting and stopping an asynchronous motor by way of a soft starter. The method includes the following steps: determining ignition options of one or more thyristors of the soft starter that are possible at a future calculation time; predicting the motor behavior for the determined ignition options, if an ignition of one or more thyristors of the soft starter is carried out; based on the predicted motor behavior, deciding whether an ignition option is to be selected and which is to be selected; and generating one or more ignition signals for one or more thyristors, if the decision for an ignition option has been made.

First claim

The invention claimed is:

1. A method for starting and stopping an asynchronous motor by a soft starter comprising thyristors connected in antiparallel in switchable phases, the method comprising the following steps:
ascertaining all firing opportunities available for the thyristors of the soft starter at a calculation time in the future;
forecasting, for all the firing opportunities thus ascertained, an electrical and/or mechanical motor behavior corresponding to the firing opportunities;
deciding, based on the motor behavior thus forecast, whether and which firing opportunity is to be chosen;
if a decision has been made to take a specific firing opportunity, generating one or more firing signals for one or more thyristors as a result of which anticipated motor behavior is established;
repeatedly ascertaining a present rotor angle, a present rotor speed, a present grid phase angle, and present stator phase currents;
using the present rotor angle, the present rotor speed, the present grid phase angle, and the present stator phase currents to anticipate a torque response for a torque acting on a rotor for first firing opportunities, in which a firing of thyristors turns on two phases, and for a second firing opportunity, in which firing of thyristors turns on three phases; and
using the torque responses thus anticipated to decide whether each thyristor is fired.

2. The method according to claim 1 , which comprises ascertaining the firing opportunities for a respectively following time step.

3. The method according to claim 1 , which comprises modelling the motor behavior by a transient motor model.

4. The method according to claim 1 , wherein the deciding step comprises making a decision based on one or more decision criteria selected from the group consisting of: maximum stator current, maximum torque, minimum on-time for thyristors, minimum average torque, maximum rotor flux, minimum rotor flux growth as a result of the firing, thyristor losses, and motor losses.

5. The method according to claim 1 , which comprises not firing at an immediate next calculation time and awaiting the forecast for a calculation time that follows the immediate next calculation time if a decision is made that a firing opportunity is not useful.

6. The method according to claim 1 , which comprises ascertaining only firing opportunities that result in negative torques that actively slow down the asynchronous motor.

7. The method according to claim 1 , which comprises preceding the step of ascertaining firing opportunities with a step of magnetic flux generation in the rotor by way of firings of the thyristors.

8. The method according to claim 7 , which comprises generating the magnetic flux in the rotor by way of two-phase firings of the thyristors at always the same grid phase angle.

9. A soft starter, comprising a firing signal unit and a device configured to carry out the method according to claim 1 .

10. A computer program product, comprising computer-readable instructions that cause a soft starter with a firing signal unit and a processor to carry out the method according to claim 1 .

11. A non-transitory computer-readable medium containing a computer program product with instructions for a processor of a soft starter to carry out the method steps according to claim 1 .

Assignees

• Siemens Ag

Inventors

• Nannen Hauke
• Zatocil Heiko

Classifications

• H02P2207/01

  Asynchronous machines · CPC title

• H02P1/26 Primary

  for starting an individual polyphase induction motor · CPC title

• H02P27/024

  using AC supply for only the rotor circuit or only the stator circuit · CPC title

• H02P21/20

  Estimation of torque · CPC title

• H02P21/13

  Observer control, e.g. using Luenberger observers or Kalman filters · CPC title