RU1802905C - Method of determination of friction coefficient of start off of electric machine - Google Patents

Abstract

SUMMARY OF THE INVENTION: a method includes the use of weights suspended from a shaft at a loading and receiving area. To implement the proposed method, the electric machine is mounted on the technological stand 20, providing the necessary height for installing the measuring device, then the rocker 1 is mounted on the end of the shaft 17 of the electric machine 18 with equal shoulders and load pads 6 at the ends of the rocker arm and fixed in the middle rocker arm, perpendicular to it with a pointer 15 with a scale 17 at the end, and the electric machine is set so that the middle of the scale 17 coincides with the tip of the arrow of the decree He ate 15, then put the standard weights 7 on one of the lifting platforms 6 until the arrow deviates by one division, which corresponds to a rotation of the rotor by 1 °, then the weights 7 are moved to the second platform 6, the rotor returns to its original position, produces several measurements, determine the average value and find the moment of starting and friction coefficient of starting. 4 ill.

Description

The invention relates to measuring equipment, in particular to measuring the mechanical quantities of various mechanisms, including electrical machines.

The aim of the invention is to remedy these drawbacks, i.e., to increase the accuracy and quality of measurements in determining the friction coefficient.

In FIG. 1 shows a measuring device mounted on an end of a motor shaft; in FIG. 2 shows an embodiment of fastening the device to a hollow shaft; in FIG. 3 - power receiving support: in FIG. 4, a measuring device illustrating the method adopted for the prototype ... .

The device contains (Fig. 1) rocker 1 with equal shoulders. At each end of the rocker T there are triangular prisms

2.with blade, earring 3, pillow 4, earrings 3 with a triangular groove to support the prism blade. To earring 3 using hinge 5. suspended load receiving platform 6, which set the reference weights 7 when measuring. The lifting platform is connected to the hinge 5 by means of arches 8. At the ends of the rocker arm 1, torpedo weights 9 are installed. nut 14 (Fig. 2). Perpendicular to the rocker arm 1, a pointer arrow 15 is mounted in the middle thereof. The opposite end of the arrow is provided with a counterweight 16, and the pointer end of the arrow has a scale 17. The device is mounted 00

about

go

It is based on the electric motor 18. The rocker 1 is set to level 19 to check the horizontal position of the electric motor. An electric motor 18 is mounted on the technological stand 20 to provide the necessary height for the winding of the measuring device.

Before mounting the device on an electric motor 18, it must be installed on a rack. A T-5000 type of technical scale and the system must be adjusted with the help of the weighed loads, then removed from the rack of the technical scale and installed on the electric motor 18, which is placed on the technological stand 20, at the same time, the load receiving platforms 6 should be in a freely suspended state. The pointer arrow 15 is set at an angle of 90 ° to the horizontal axis of the rocker arm 1 and to the axis of the electric motor 18, while the electric motor must be installed strictly horizontally. Its horizontal position is controlled by level 19, the index scale 17 is mounted directly on the electric motor 18, so that its middle coincides with the tip of the arrow 15.

To measure the moment of starting, reference weights 7 are placed on one of the platforms 6 until the arrow 15 deviates by one division, which corresponds to a rotation of the rotor by 1 °. Then the weights 7 are moved to the second platform 6, the rotor must return to its original position, if there is a deviation in the weight of the weights, then you need to take the average value, make several measurements. When measuring the moment of starting in seawater, the electric motor is installed in the process tank, the measuring device is mounted, then the tank is filled with artificial sea water until the bearings are immersed in water. In the case of a monolithic motor shaft, the device is fixed directly to the shaft end through the adapter sleeve (not shown in the drawings). After taking readings and determining the average value of the weight Fr, the starting moment Mtrog and the friction coefficient of starting FTp trog are determined according to the procedure:

Mtrog-FV-I ,. (1)

where I is the arm length of the rocker arm

(2)

Mtrog. - Rtr.trog d / 2,

where Rtr.trog is the friction force of moving;

d is the diameter of the sleeve (shaft journal) of the sliding bearing

Frp.Tpor Fpor ftp.trog, (3)

where Roth is the weight of the rotor.

Equating in (1) the formula to (2) taking into account (3), we obtain:

5 U 15 20 5

30 35 40 45

fifty

Trt.trog

Fr-i

(4)

55

FPOT d / 2

The friction coefficient of friction according to formula (4) will be several times greater than the coefficient of friction in bearings under steady state conditions.

This increase can be determined from the ratio of the moment of friction in the steady state to the moment of starting.

The frictional moment during operation of the electric motor is determined from the friction losses

bearings, that is: p. Subway 975 -, (5)

where P is the loss in bearings in kW;

u - synchronous speed, rpm.

Dividing the formula (1) by the formula (5), we obtain a quantitative value of the increase in the coefficient of friction in relation to the coefficient of decay during operation of the electric motor

Mtrog tChr.trog Fa I P1

t m

tr.podsh

ttr

975 R

The determination of the starting moment according to the proposed technical solution corresponds to reality and these results are necessary for calculating the starting torque of the electric motor, which starts, provided that

MPR Mt.trog + Mdin,

where Mdin is the dynamic moment determined by the rotor masses.

In the absence of friction in the support of the earring 3 in this case, on the arm of the rocker arm 1, equal to 200 mm, and the weight of weights up to 5 kg, the measurement error is 300 mGs or 0.3 Hz, which corresponds to high accuracy and meets the requirements of GOST 23676-79 .

The technical and economic advantages of the claimed method as compared with the prototype consist in increasing the accuracy and quality of measurements of the friction coefficient of the starting of an electric machine, the results of which are necessary for calculating the starting moments of these machines. In addition, the claimed method is applicable to all types of electric machines when measuring the friction coefficient of friction in air, in liquid media and sea water.

Claims (1)

Formula from acquisition A method for determining the coefficient of friction of starting an electric machine, including the use of weights suspended from a shaft at a load receiving area, characterized in that, in order to improve the accuracy and quality of measurements, the electric machine is installed on the technological support, providing the necessary height for the installation of the measuring device, is then mounted on the shaft end of the electric machine with a beam with equal shoulders and load platforms at the ends and fixed in the middle of the beam, with a pointer perpendicular to it with a scale at the end, set the electric machine so that the middle of the scale coincided with the arrowhead of the pointer, then put the standard weights on one of the load platforms until the arrow deviates by one division, which corresponds to a rotation of the rotor by 1 °, then the weights are moved to the second platform, the rotor returns to its original position, several measurements are made, the average value is determined and the starting moment and friction coefficient of starting are found. (rmg. 2 Editor T. Kol yes Compiled by T. Tropacheva Tehred M. Morgenthal Corrector P. Gereshi