CN213302460U

CN213302460U - Device for detecting three-phase unbalance of motor

Info

Publication number: CN213302460U
Application number: CN202022494612.4U
Authority: CN
Inventors: 朱勇; 于鑫军; 杨增慧; 赵永江; 张宝柱
Original assignee: Shanqi Heavy Machinery Co ltd
Current assignee: Shanqi Heavy Machinery Co ltd
Priority date: 2020-10-31
Filing date: 2020-10-31
Publication date: 2021-05-28
Anticipated expiration: 2030-10-31

Abstract

The utility model discloses a detect unbalanced device of motor three-phase belongs to the motor and detects technical field, including three the first current transformer who establishes ties respectively on the three-phase input line of motor once side, it is three the secondary side of first current transformer establishes ties and once inclines at second current transformer, second current transformer's secondary side is connected with the current detection unit, and when three-phase current balance, the electric current of current detection unit input is zero, and when three-phase current had slight unbalance, the current detection unit just can detect the electric current to in time remind the staff to overhaul, avoid the production loss of heaviness.

Description

Device for detecting three-phase unbalance of motor

Technical Field

The utility model belongs to the technical field of the motor detects, concretely relates to detect unbalanced device of motor three-phase.

Background

The winding motor of the crane in the steel mill has large starting current ratio and frequent work due to frequent starting, positive rotation and reverse rotation, and the following hazards can be generated if the current of the three-phase winding motor is unbalanced:

1. when the rotating motor runs in an asymmetric state, the rotor can generate additional loss and generate heat, so that the whole or local temperature rise of the motor is caused, in addition, the motor can vibrate due to the additional moment generated by a reverse magnetic field, and for a generator, a series of higher harmonics can be formed in the stator;

2. for a generator, when three-phase load is unbalanced, if the maximum phase current is controlled to be a rated value, the other two phases cannot be fully loaded, so that the utilization rate of equipment is reduced, otherwise, if the rated capacity is maintained, overload of one phase with larger load is caused, waveform distortion caused by unbalanced magnetic circuits is caused, additional loss of equipment is increased, and the like.

The three-phase motor current of the winding motor of the crane in the steel mill is unbalanced, if the current is found out untimely, the motor can be burnt out finally after long-time running, the crane is stopped, the production of the steel mill is influenced finally, and great loss is caused. Therefore, a device capable of timely finding out the small unbalance of the three-phase current of the motor is needed, the small unbalance of the three-phase current of the motor can be found in time when the small unbalance of the three-phase current of the motor just occurs, a plan is made to overhaul and replace the motor, and the serious production loss is avoided.

SUMMERY OF THE UTILITY MODEL

The utility model discloses the technical problem that will solve is: the utility model provides a detect unbalanced device of motor three-phase can in time discover when the motor just appears small three-phase current unbalance, makes things convenient for the maintainer to overhaul the change, avoids the production loss of great weight.

In order to solve the technical problem, the technical scheme of the utility model is that:

the device for detecting the three-phase unbalance of the motor comprises three first current transformers, wherein primary sides of the three first current transformers are respectively connected with a three-phase input line of the motor in series, secondary sides of the three first current transformers are connected with a primary side of a second current transformer in series, and a current detection unit is connected with the secondary side of the second current transformer.

Further, the current detection unit is a current relay.

Furthermore, the output end of the current relay is electrically connected with the alarm unit.

Further, the output end of the current relay is electrically connected with a control loop of the motor.

Furthermore, the three-phase input line is respectively connected with a third current transformer in series, and the three third current transformers are respectively connected with an ammeter and then are grounded in parallel.

Further, the ammeter is a mechanical ammeter.

Furthermore, a power circuit breaker is connected to the three-phase input line.

Further, the three-phase input line is connected between a stator binding post of the motor and a power supply, and a rotor binding post of the motor is connected with a rotor resistor.

After the technical scheme is adopted, the beneficial effects of the utility model are that:

because the utility model discloses a detect unbalanced device of motor three-phase includes that three once establishes ties respectively the first current transformer on the three-phase input line of motor, three first current transformer's secondary side is established ties and is establishing ties and establish ties at the side once of second current transformer, second current transformer's secondary side is connected with the current detection unit, when three-phase current is balanced, the electric current of current detection unit input is zero, when three-phase current has slight unbalance, the current detection unit is with regard to detectable electric current, thereby in time, remind the staff to overhaul.

Drawings

Fig. 1 is a schematic circuit diagram of the device for detecting three-phase unbalance of the motor of the present invention.

Detailed Description

The present invention will be further explained with reference to the drawings and examples.

All directions referred to in the present specification are based on the drawings, and represent relative positional relationships only, and do not represent absolute positional relationships.

As shown in fig. 1, the apparatus for detecting three-phase unbalance of a motor comprises three first current transformers (CT1, CT2, CT3) with primary sides respectively connected in series with three-phase input lines of the motor M, wherein the secondary sides of the three first current transformers (CT1, CT2, CT3) are connected in series with the primary side of a second current transformer CT4, and the secondary side of the second current transformer CT4 is connected with a current detection unit. Wherein, the current detection unit is a current relay KA.

The output end of the current relay KA can give an alarm through the alarm unit when the three-phase current of the alarm unit is slightly unbalanced. The output end of the current relay KA can also be electrically connected with a control loop (not shown in the figure) of the motor M, and when the three-phase current is slightly unbalanced, the motor M is controlled to stop rotating so as to avoid burning the motor M after long-time operation.

As shown in fig. 1, the three-phase input lines are respectively connected in series with third current transformers (CT5, CT6, CT7), and the three third current transformers (CT5, CT6, CT7) are respectively connected with ammeters (PA1, PA2, PA3) and then are connected in parallel with the ground. The ammeters (PA1, PA2 and PA3) are all mechanical ammeters. The specific current value of the three-phase current is convenient for the staff to check.

As shown in fig. 1, a power breaker QF is connected to a three-phase input line, the three-phase input line is connected between a stator terminal (U, V, W) of the motor M and a power supply AC, and a rotor terminal (K, L, M) of the motor M is connected to rotor resistors (R1 to R4).

The utility model discloses a detect unbalanced device of motor three-phase is through concatenating first current transformer on the three-phase input line of motor respectively, and three first current transformer's secondary side is established ties and is once inclining at second current transformer, and second current transformer's secondary side is connected with the current detection unit, and when three-phase current had slight unbalance, the current detection unit just can detect the electric current to in time remind the staff to overhaul, avoid the production loss of heaviness.

Although specific embodiments of the present invention have been described above, it should be understood by those skilled in the art that the described embodiments are only some of the embodiments of the present invention, rather than all embodiments, which are given by way of illustration only, and the scope of the present invention is defined by the appended claims. Without any inventive step, those skilled in the art can make various changes or modifications to the embodiments without departing from the spirit and scope of the present invention.

Claims

1. The device for detecting the three-phase unbalance of the motor is characterized by comprising three first current transformers, wherein primary sides of the three first current transformers are respectively connected with a three-phase input line of the motor in series, secondary sides of the three first current transformers are connected with a primary side of a second current transformer in series, and a current detection unit is connected with the secondary side of the second current transformer.

2. The apparatus for detecting three-phase imbalance of an electric motor according to claim 1, wherein the current detecting unit is a current relay.

3. The apparatus for detecting three-phase imbalance of an electric motor of claim 2, wherein the output of the current relay is electrically connected to an alarm unit.

4. The apparatus for detecting three-phase imbalance of an electric motor of claim 2, wherein the output of the current relay is electrically connected to a control loop of the electric motor.

5. The apparatus for detecting three-phase imbalance of an electric motor according to claim 1, wherein the three-phase input lines are respectively connected with third current transformers in series, and the three third current transformers are respectively connected with an ammeter and then are grounded in parallel.

6. The apparatus for detecting three-phase imbalance of an electric machine of claim 5, wherein the current meter is a mechanical current meter.

7. An apparatus for detecting three phase imbalance of an electric motor according to any one of claims 1 to 6, wherein a power circuit breaker is connected to the three phase input line.

8. The apparatus of claim 7, wherein the three phase input line is connected between a stator terminal of the motor and a power source, and a rotor resistor is connected to a rotor terminal of the motor.