SU817877A1 - Device for improving the switching of commutator electric machines - Google Patents

Description

(54) DEVICE FOR IMPROVED COMMUTATION OF MANIFOLD ELECTRIC MACHINES

The invention relates to electric machines, in particular, to means of improving the commutation of collector electric machines with a rotational frequency regulated over a wide range. Devices for improving commutator commutator electric machines are known, which contain an adjustable power source connected to the main or auxiliary winding of additional poles, functional elements, Hall EMF sensors acting as current, flow or multiplying sensors, a rotational speed sensor, and other elements 1. The Hall EMF sensors in these devices, according to whatever scheme they are turned on, ultimately have a signal at the output proportional to the current of the core with speed correction Vrash, Yeni or s compensation for the flow of additional poles. And in this and in other cases, the signal applied to the input of the controlled amplifier does not fully take into account the nature of the switching (slowed down or accelerated). Although only a signal proportional to the additional switching current, determines the accuracy and stability of the switching setting in the middle of the sparkless zone. It is also known a device for improving the switching of DC machines with windings of additional poles, comprising a controllable amplifier, a main or auxiliary windings of the additional poles, a current sensor and a voltage sensor. The regulation of the flow of the additional poles is carried out as a function of the voltage along the running and rising edges of the brush with current correction of the core and occurs until a value favorable from the switching point of view is obtained. It is known that in multi-pole machines with wave winding, the core of the switched section is short-circuited by two brushes and the bus connecting them. In one brush, the additional switching current coincides with the current of the parallel branch, and in the other it is directed oppositely. The current density in the brushes of the same polarity will be different and the voltage between the incident and escaping edges of any brush in this case will not fully characterize the switching conditions 2. The presence of a contact sensor reduces the reliability and stability of the device, since when the core rotates, it is possible for the brush to tip over, detach it from the collector, etc. To improve the accuracy, reliability and stability of such a device can use a contactless sensor, the output of which the signal is proportional to the additional switching current.

The closest in technical essence and the achieved effect to the proposed is a device for improving the switching of direct current electrical machines (MPT) operating with variable load. This device contains auxiliary windings placed on the cores of the additional poles, an amplifier for powering the auxiliary windings and elements for controlling the amplifier. Two Hall sensors are used as control elements, one of which is installed in the air gap under the additional pole, and the other in the gap of the magnetic circuit covering the bus with the core current. Hall sensor output circuits are connected in series. The regulation of the magnetic flux of the additional poles is carried out as a function of the difference of signals proportional to the current of the core and the flux of the additional poles 3.

A device with such placement and inclusion of Hall sensors allows to improve the switching conditions of the MPT only when the load is reset and the load is applied at one frequency of rotation of the core.

When the rotational speed of the PST is changed by weakening the field in the wide range, the switching becomes more accelerated and for sparking-free operation a smaller flow of additional poles is required, which requires automatic adjustment of the additional poles to the operation of the PTA in the middle of the searchless zone. In this case, the only correct approach is to regulate the flow of additional poles for the operation of the MPT in the middle of the sparking-free zone as a signal proportional to the additional switching current.

The purpose of the invention is to improve the accuracy, stability and reliability of setting switching commutator electric machines in the middle of the sparkless zone.

The goal is achieved by the fact that the device is equipped with an additional magnetic conductor, the excitation winding of which is connected in series with the winding of the main pole, and the second Hall EMF sensor is installed in the gap of the additional magnetic conductor.

The drawing shows the device in principle block diagram.

The device consists of a controlled amplifier 1, connected to the main winding 2 of the additional poles 3. As a controlled amplifier, a semiconductor magnetic or thyristor amplifier can be used. To obtain a signal proportional to the additional switching current, two Hall EMF sensors were used. Hall sensor 4 is installed under the center of the main pole 5 and its output

.. The emf is proportional to the resulting flow in the air gap of the machine. The Hall sensor 6 is installed in the air gap of the magnetic circuit 7 with a winding 8 connected in series with the excitation winding 9 placed on the main poles 5. The output

The EMF of the Hall sensor 6 is proportional to the magnetic flux created by the excitation winding 9 in the air gap under the main pole 5. The current circuits of both sensors are powered from an independent power source. Hall sensor circuits are included in the compensation circuit and the output emf is equal to the difference in output emf of both sensors. Such inclusion of the Hall sensors ensures the operation of the device while controlling the rotation frequency

5th floor

In the case of straight-line switching, when the flow of the switching reaction of the box Fa.is absent, the signal at the output of controlled amplifier 1 is equal to zero and in the winding 2 additional poles 3 connected to

 the output of the amplifier 1, flows only the current box.

in the case of accelerated switching, the flow of the switching reaction of the Phage core, as seen in the drawing, where the directions of the currents are shown for the accelerated switching of the DC motor when rotated counterclockwise, will be directed opposite to the main magnetic flux Fd. The resultant flow below the center of the main pole 5 decreases and at the input of amplifier I

0 according to Wits differential emf of a certain polarity. Amplifier 1 will work out this signal and a siphon current will flow in winding 2, which will reduce the magnetizing force of the additional poles. An automatic reduction of the magnetizing force of the additional poles 3 will occur until the switching becomes linear, which contributes to the adjustment of the searchless zone to the middle.

0s

If the switching becomes slow with the same direction of rotation, the flow direction changes Fock, the polarity of the signal at the input of amplifier 1 and the direction of current at the output of amplifier I will change, which will increase the magnetizing force of the additional poles 3. And just like in the previous In this case, the switching will be automatically adjusted to the middle of the sparkless zone.

The proposed device for improving commutator switching of electric machines through the use of a contactless sensor of auxiliary switching current provides an accurate and reliable, and very importantly, stable setting of the additional poles to the middle of the searchless zone for any changes in the parameters of the switched circuit and the operating mode of the collector electric machine any type of winding box.

Claims (3)

1. USSR author's certificate number 248048, cl. H 02 K 13/14, 1969 2. The patent of Germany No. 1200930, cl. 21 d 28 1965. 3. USSR author's certificate number 181181, cl. H 02 K 23/24, 1965.