SU144211A1 - The method of controlling the electric mechanisms of the stop - Google Patents

Description

The invention relates to electric AC drives operating on a stop.

Various methods are known for controlling electric drives of stop mechanisms.

The proposed method differs from the known ones in that the torque is increased when starting over the moment of stopping, for which the engine is normally fed through a resistance connected in series to the stator circuit, which is turned off during the start-up period. This method makes it possible to increase the reliability of the AC drives of the mechanisms with self-braking by push-pull gears (healed devices, stop valves, etc.).

FIG. 1 shows as an example the control circuit of a reversible asynchronous electric motor of a mechanism operating on unor, in which the proposed method is implemented; in fig. 2 shows the mechanical characteristics of the electric motor: natural - / and artificial - 2 with the resistance introduced into the stator circuit, / I, - the line of the momentum of static resistances of the mechanism.

The motor D is connected to the mains by the contacts of the reversing contactors B and I. To limit the torque of the motor D, when stopped in series with the stator winding, resistances Y are connected (active for low power motors or inductive for high power motors). During start-up and rotation with an adjustable speed, the resistance R is clamped by the normally closed contacts of the contactor T.

The magnitude of the starting torque Mn (Fig. 2) is chosen such that it is greater than the sum of the engine torque when stopped with the resistance entered, the dynamic torque of the drive when stopped and

No. 144211-2 -

additional moment of resistance arising due to changes in the coefficient of friction, jamming, etc. The drive is started in the right direction by pressing the KB button (forward) or KN (reverse). The stop button KS is used to emergency stop the drive.

End protection is provided by the limit switches KVV and KVN.

The 1PB and 2PV time relays have different trigger settings. The time delay of the 1PB relay ensures that the reversing VN contactors are disconnected after a time sufficient for the mechanism to travel from one extreme position to another. The 2PB relay has such a time delay in order to ensure that the contactor T is turned on (and thus to introduce resistance into the stator circuit) before the motor is disconnected from the network.

Subject invention

Control method: electrically driven mechanisms that work on the thrust, which means that, in order to increase reliability

electric drive and simplification, transmission by exceeding the torque at start-up with the lead moment at stop, in normal mode, the motor is fed through a resistance connected in series to the stator circuit, which is turned off (bridged) during the start-up period.