CN105486427A - Permanent magnet motor permanent magnet body temperature rise calculating method - Google Patents

Abstract

The invention relates to a permanent magnet motor permanent magnet body temperature rise calculating method. The method comprises the following steps: 1) measuring zero-load back electromotive force E01 of a motor under a cold state; 2) measuring zero-load back electromotive force E02 of the motor under a thermal state; 3) calculating the value of phi02/ phi01 according to inherent characteristics of the permanent magnet motor; 4) calculating the ratio Br/ Br0 of residual magnetism magnetic density Br of a permanent magnet body in thermal-state working and residual magnetism magnetic density Br0 of the permanent magnet body in cold-state working; and 5) obtaining the difference value (t-t0) between the thermal-state temperature t of the permanent magnet body and cold-state temperature t0 thereof through a calculation formula: (t-t0)=(1- Br/ Br0)/ [alpha]br, the difference value being temperature rise of the permanent magnet body. The temperature rise of the permanent magnet body is calculated by utilizing change of ratio between the zero-load back electromotive forces output by the permanent magnet motor under the cold state and the thermal state respectively, and working temperature rise and actual working temperature of the permanent magnet motor permanent magnet body can be accurately obtained without installing any temperature measuring device and other accessory devices to the motor, thereby providing basis for optimal selection of temperature resistance level of the permanent magnet motor permanent magnet body.

Description

A kind of permanent magnet temperature rise measuring method of magneto

Technical field

The present invention relates to technical field of motors, particularly relate to a kind of permanent magnet temperature rise measuring method of magneto.

Background technology

When magneto runs there is eddy current loss in permanent magnet inside, making permanent magnet temperature increase, as exceeded the temperature resistant grade of permanent magnet, permanent magnet will be caused to produce irreversible loss of excitation, even scaling loss.For ensureing the reliability of magneto product, in the new product development stage, the permanent magnet temperature rise of model machine measures very necessary, and its data can be used for the temperature resistant grade instructing preferred permanent magnet.

Generally, permanent magnet of permanent magnet motor is positioned on rotor, is in rotation status during operation.Adopt the technology such as existing embedding temperature element, wireless temperature measurement, need increase temperature measuring equipment on rotor permanent magnet, it is installed and data acquisition is implemented complicated, and the also more difficult internal temperature recording permanent magnet, the data error recorded is large.

Summary of the invention

For overcoming the deficiencies in the prior art, the invention provides a kind of implement simple, the permanent magnet temperature rise measuring method of calculation of measured data magneto accurately.

For achieving the above object, technical scheme of the present invention is: a kind of permanent magnet temperature rise measuring method of magneto, and it comprises the following steps:

Step 1: record the empty load of motor back electromotive force E under cold conditions ₀₁;

Step 2: motor carries out temperature rise test, after temperature rise is stable, records the hot no-load back electromotive force E of motor ₀₂;

Step 3: according to magneto inherent characteristic, the hot unloaded main flux Φ of motor ₀₂main flux Φ unloaded with motor cold conditions ₀₁ratio Φ ₀₂/ Φ ₀₁with E ₀₂/ E ₀₁be worth equal, thus obtain Φ ₀₂/ Φ ₀₁value;

Step 4: adopt existing magneto Computational Electromagnetic Methods, utilize Φ ₀₂/ Φ ₀₁value, obtains the close B of permanent magnet hot work remanent magnetism magnetic _rwith the close B of permanent magnet cold operation remanent magnetism magnetic _r0ratio B _r/ B _r0;

Step 5: draw permanent magnet hot temperature t and cold-state temperature t according to computing formula (1) ₀difference (t-t ₀), be the temperature rise of permanent magnet;

$(t-t_0)=(1-\frac{B_r}{B_{r0}})/{\mathrm{\α}}_{B_r}---\left(1\right)$

In formula, for the temperature coefficient of permanent magnet.

The invention has the beneficial effects as follows: this method utilizes the ratio of magneto cold conditions and hot lower output no-load back electromotive force to change, the temperature rise of measuring and calculating permanent magnet, any temperature measuring equipment and other auxiliary equipments need be installed on motor, accurately can draw operating temperature rise and the actual work temperature of permanent magnet of permanent magnet motor, for the optimum option of permanent magnet of permanent magnet motor temperature resistant grade provides foundation.

Embodiment

Below in conjunction with embodiment, the present invention is further illustrated.

A permanent magnet temperature rise measuring method for magneto, it comprises the following steps:

Step 1: motor is moved to rated speed, idle condition, motor is in cold conditions, records motor cold conditions no-load back electromotive force E ₀₁, now in motor, the temperature of permanent magnet is consistent with environment temperature, and the environment temperature simultaneously recorded is the temperature t of permanent magnet ₀;

Step 2: motor carries out temperature rise test, after temperature rise is stable, lay down motor load immediately, motor is rated speed, idle condition, and is in hot, records the hot no-load back electromotive force E of motor ₀₂;

Step 3: according to magneto inherent characteristic, magneto Φ ₀₂/ Φ ₀₁with E ₀₂/ E ₀₁value equal, obtain the hot unloaded main flux Φ of motor ₀₂main flux Φ unloaded with motor cold conditions ₀₁ratio Φ ₀₂/ Φ ₀₁;

Step 4: adopt existing magneto Computational Electromagnetic Methods, utilize Φ ₀₂/ Φ ₀₁value, obtains the close B of permanent magnet hot work remanent magnetism magnetic _rwith the close B of permanent magnet cold operation remanent magnetism magnetic _r0ratio B _r/ B _r0;

Step 5: according to computing formula: draw permanent magnet hot temperature t and cold-state temperature t ₀difference (t-t ₀), the hot working temperature t of permanent magnet can be obtained, in formula, for the temperature coefficient of permanent magnet, as the temperature coefficient of rare-earth Nd-Fe-B permanent magnet be generally-0.11%, the temperature coefficient of rare earth SmCo permanent magnet is generally-0.03%.

Principle of the present invention is: the magnetic flux that permanent magnet provides affects by its working temperature, and influence coefficient is steady state value, i.e. the temperature coefficient of permanent magnet; As Nd-Fe-B permanent magnet working temperature t often rises 1 DEG C, the close B of its work remanent magnetism magnetic _rdecline 0.11%.The unloaded main flux of magneto is only provided by permanent magnet, and when rotating speed is constant, the no-load back electromotive force that unloaded main flux exports to motor is directly proportional.Therefore, calculate by the changing value of empty load of motor back electromotive force the temperature change value drawing permanent magnet, i.e. the temperature rise of permanent magnet, data accurately and reliably.

Claims (1)

1. a permanent magnet temperature rise measuring method for magneto, it is characterized in that, it comprises the following steps:

Step 1: record the empty load of motor back electromotive force E under cold conditions ₀₁;

Step 2: motor carries out temperature rise test, after temperature rise is stable, records the hot no-load back electromotive force E of motor ₀₂;

Step 3: according to magneto inherent characteristic, the hot unloaded main flux Φ of motor ₀₂main flux Φ unloaded with motor cold conditions ₀₁ratio Φ ₀₂/ Φ ₀₁with E ₀₂/ E ₀₁be worth equal, thus obtain Φ ₀₂/ Φ ₀₁value;

Step 4: adopt existing magneto Computational Electromagnetic Methods, utilize Φ ₀₂/ Φ ₀₁value, obtains the close B of permanent magnet hot work remanent magnetism magnetic _rwith the close B of permanent magnet cold operation remanent magnetism magnetic _r0ratio B _r/ B _r0;

Step 5: draw permanent magnet hot temperature t and cold-state temperature t according to computing formula (1) ₀difference (t-t ₀), be the temperature rise of permanent magnet;

$(t-t_0)=(1-\frac{B_r}{B_{r0}})/{\mathrm{\α}}_{B_r}---\left(1\right)$

In formula, for the temperature coefficient of permanent magnet.