SU109478A1 - Method of dynamic braking of mine hoists with asynchronous drive - Google Patents

Description

The subject of the invention is a method of dynamic braking of mine hoisting machines with asynchronous drive using magnetic amplifiers.

Applied devices for dynamic braking of mine hoists with an asynchronous drive do not allow the descent of the load at the desired steady speed. In addition, in the known devices of this kind, the possibilities that the use of feedback between the rotor and the stator does not fully utilize and that the lifting installation is not automatically controlled during the deceleration period.

The described method allows to eliminate these drawbacks.

This is due to the fact that the rate of ascent or descent of the cargo vessel of the lifting installation uniquely determines the mixing magnitude 1 1 of the magnetic amplification. This mixing is controlled by a control knob or automatically by means of a retardiruyush, its disk and a device consisting of windings facing each other, selenium rectifiers and an inductive impedance controller.

The drawing shows the electrical circuit of the device for dynamic braking of mine hoisting machines.

The source of direct current for carrying out dynamic braking of the asynchronous motor of the AD installation of the lifting installation is a generator of gas turbine engines or a choke force, with selenium rectifiers. The feedback of the stator of the asynchronous motor AD with the rotor is performed by iC using current transformers CT and rectifiers B, included in the rotor circuit. The signals from the CT current transformers are amplified using a single-ended magnetic amplifier MU having a control winding W, a Woe feedback winding two alternating current windings Wn and Wn., And two oppositely connected bias windings WCM and WCM. From the release of ma, Ye 109478- 2 -

The amplified amplifier amplified signals are supplied to the excitation winding W of the generator of a GNDT or saturation throttles.

The regulation of the rotational speed of the motor BP in the dynamic braking mode is carried out by a device that changes the magnitude of the bias of the magnetic amplifier. This device can operate both automatically from the retardating disk of the POISON of the lifting installation, and from the control handle of the management team. These organs act on the inductor impedance regulator RIS included in the depy of both windings bias W oc and W g. "G magnetic amplifier.

The control current of the magnetic amplifier is proportional to the speed of rotation of the rotor, since the CT current transformers operate in the Pi mode.

A transformer T and three selenium rectifier bridges BMi, BMz and VMz are provided for powering the magnetic amplifier MU and the excitation winding of the hyperatra of the GDT.

A change in the resistance of the rheostat in the rotor circuit is made automatically by means of contactors 1U-6U, controlled by the corresponding time relays.

For the purpose of additional control over speed, voltage controllers PHi, PH and RYAZ are introduced into the control circuit of contactors 1U-6U, the windings of which are connected in parallel with the control winding Wy of the magnetic amplifier.

The descent of the load at a newer speed with a subsequent slowdown is carried out, according to the proposed method, in the following manner.

The machinist moves the control handle of the switchgear to the extreme position, presses the high-speed button of the PIC and activates dynamic braking. In this case, the time relays will, at certain intervals, turn on the contactors 1U-6U, bypassing the individual stages of the start-regulating rheostat.

The resistance of this rheostat will decrease to a value corresponding to a given descent rate, i.e., the initial displacement of the magnetic amplitude l M MU.

Further reduction of resistance will not occur, since the circuit of one of the accelerator contactor coils will be opened by the normally closed contact of the PBC relay, which opens when pressing the button of the high-speed FAC.

Thus, the descent of the load will occur at an increased speed, corresponding to a given initial displacement of the MU, and with optimal resistance in the rotor circuit of the electric motor HELL.

At a certain distance of the cargo vessel from the receiving platform, the retarding RD disc, acting on the inductor resistance indicator RIS, reduces the bias of the magnetic amplifier, and the limit switch PV opens the RVS relay circuit. As a result, there is a sharp decrease in the speed of rotation of the engine, and consequently, the speed of the descent of the cargo vessel.

The final stop is provided by a mechanical brake.

The descent of the load at creeping speed can be easily accomplished by moving the profile of the retarding disk so that it immediately affects the magnitude of the displacement of the magnetic amplifier (and the machinist does not press the FAC button).

In automatic lifting installations, the initial magnitude of the magnetic amplifier is strictly determined. In this case, the retardating disk must have two profile cams, respectively, for lowering and lifting.