SU613242A1 - Device for measuring inductor induction motor r.p.m. - Google Patents

Description

one

The invention relates to a control and regulation technique and can be used to measure the rotational speed of inductor asynchronous machines.

Nowadays, digital velocity gauges 1, which use various types of velocity sensors, are becoming increasingly common.

The closest in technical essence and solvable problems is a device for measuring the speed of an induction motor 2, which contains drivers connected to the secondary winding of an induction motor and through a capacitor to a power supply, a signal extraction unit and a frequency meter.

The disadvantages of the known speed meter include low measurement accuracy.

The purpose of the invention is to improve the accuracy of measuring the rotational speed.

For this, the outputs of the drivers are connected to a signal extraction unit loaded on a frequency meter, and the unit itself is designed as a phase-sensitive rectifier.

The drawing shows a structural electrical circuit of the device.

The proposed device contains a signal extraction unit 1, amplifiers-formers 2 and a frequency meter 3. The signal isolation unit consists of a phase-sensitive rectifier 4 and a filter 5. The inputs of amplifiers 2 are connected to the secondary windings 6 and 7 of the induction induction motor being tested 8,

and the outputs are connected to the inputs of the phase-sensitive rectifier 4. The output of the phase-sensitive rectifier 4 is connected through the filter 5 to the input of the frequency meter 3.

Both secondary windings 6 and 7 are sealed by capacitors 9 and 10. The windings of the AND and control 12 of the test motor 8 are connected to the power source 13.

The operation of the proposed device is based on the property of an inductor asynchronous motor, which consists in a periodic change in the phase shift between the voltages on the secondary windings during the rotation of the rotor. The period of change of phase shift is one tooth division of the rotor.

When applying from the power source 13 an alternating voltage to the excitation windings 11 and driving 12 of the test induction asynchronous motor 8, alternating currents are induced in the secondary windings 6 and 7

power frequency, while the rotor 14 begins to rotate.

The voltage from the secondary windings 6 and 7 is fed to the amplifiers 2, which maintain the amplitude of the voltages at a constant

level, as with the x load on

3

the motor shaft will also change the voltage amplitude on the secondary windings. From the amplifiers 2, the voltages are applied to the phase sensitive rectifier 4.

The phase-sensitive rectifier 4 together with the filter 5 converts a periodically varying phase shift between the input signals into an alternating voltage whose frequency is proportional to the rate of change of the phase shift between the voltages on the secondary windings 6 and 7 and, consequently, the rotor rotation speed 14.

A driver shaper 15 converts the alternating voltage that is applied to it after filtering into pulses of constant duration and amplitude. The frequency of these pulses, measured by a digital device, is a multiple of speed.

The device works reliably up to a maximum rotational speed.

15 / p

rpm

Max

where fn is the power frequency of the motor, P is the number of teeth of the rotor.

Claims (2)

1. Bogorad G. 3. and Kablitsky V. A. Digital controllers and speed meters. M., 1966, p. 54-56. 2. USSR author's certificate No. 431510, cl. G 05G 15/06, 14.02.72.