Separation method of iron loss and mechanical loss of variable frequency starting permanent magnet synchronous motor

Abstract

The application belongs to the technical field of motor testing, and discloses a method for separating iron loss and mechanical loss of a variable-frequency starting permanent magnet synchronous motor. The method realizes the separation of the motor iron loss and mechanical loss by increasing the rotational inertia of the rotor of the permanent magnet synchronous motor to be tested and using the no-load characteristic test method. The application increases the inertia tooling on the rotor of the permanent magnet motor, realizes the V / F separation control starting permanent magnet synchronous motor, avoids the step-out problem of the permanent magnet synchronous motor, realizes the acquisition of the iron loss and mechanical loss by using the no-load characteristic test of the permanent magnet synchronous motor, overcomes the problem of high cost caused by the false rotor method of the prior art, and can be directly applied to the finished motor test and has strong engineering application.

Description

Technical Field

[0001] This invention belongs to the field of motor testing technology, and specifically relates to a method for separating iron loss and mechanical loss in a variable frequency start permanent magnet synchronous motor. Background Technology

[0002] Loss measurement in variable frequency starter permanent magnet synchronous motors is a challenging aspect of the industry, especially the separation of iron losses from mechanical losses, which is a hot research topic. The ability to separate these losses directly impacts the optimization of the motor's electromagnetic design.

[0003] Permanent magnet synchronous motors, which can only be started by frequency converter control, cannot use the constant speed and voltage reduction method of traditional asynchronous motors to separate iron loss and mechanical loss because the rotor has its own permanent magnet field.

[0004] When a single permanent magnet synchronous motor is controlled using a power supply with separately adjustable voltage and frequency in variable frequency starting mode, the motor may lose synchronism and the rotor may seize up. If a frequency converter with a permanent magnet control program is used for control, the motor terminal voltage cannot be arbitrarily adjusted. This means that if the motor starting problem cannot be solved, the no-load characteristic test method for self-starting permanent magnet synchronous motors specified in GB / T 22669-2008 is not applicable to variable frequency starting permanent magnet synchronous motors.

[0005] IEEE 1814-2014 describes a dummy rotor method that can separate iron losses from mechanical losses in permanent magnet synchronous motors. This involves fabricating a non-magnetic rotor, assembling it into a complete unit, and then using a drive and torque sensor to measure the input mechanical power to obtain the mechanical losses. However, this method has the following drawbacks:

[0006] 1. The production of dummy rotors increases costs; 2. This method is difficult to implement for finished motors; 3. This method has poor engineering applicability. Summary of the Invention

[0007] To address the above problems, this invention provides a method for separating iron losses and mechanical losses in a variable frequency start permanent magnet synchronous motor. This method can separate iron losses and mechanical losses in a variable frequency start permanent magnet synchronous motor without the need to fabricate a dummy rotor. It features relatively low cost, can be directly applied to finished motor testing, and is easy to implement in engineering.

[0008] A method for separating iron loss and mechanical loss in a variable frequency start permanent magnet synchronous motor is provided, the method comprising the following steps:

[0009] S1. Increase the rotor inertia of the permanent magnet synchronous motor under test;

[0010] S2. Start the permanent magnet synchronous motor by giving voltage and frequency respectively;

[0011] S3. Measure the operating parameters of the permanent magnet synchronous motor;

[0012] S4. The iron loss and mechanical loss of the motor are obtained by using the no-load characteristic test method of permanent magnet synchronous motor.

[0013] Furthermore, the rotor inertia is increased by setting an inertia fixture on the rotor of the permanent magnet synchronous motor under test; the inertia fixture is a rotating component symmetrical about the central axis.

[0014] Furthermore, the inertia fixture includes a coupling, through which the rotor of the permanent magnet synchronous motor is connected to the rotor of another external motor.

[0015] Furthermore, before performing step S2, a dynamic balance test is performed on the permanent magnet synchronous motor under test and the inertia fixture.

[0016] Furthermore, in step S3, the operating parameters include motor voltage, current, power, resistance, and temperature.

[0017] Furthermore, in step S4, the iron loss P of the motor at its rated voltage is calculated according to formula (5). FeN ; Calculate the mechanical loss P of the electric motor according to formula (7) fw ;

[0018]

[0019]

[0020] Among them, P 0N 'For the corresponding rated voltage U N The sum of iron loss and mechanical loss under load is obtained from the no-load characteristic curve; U 01 P 01 'These are the corresponding I values ​​under weak magnetic conditions. 01 =I 0N The corresponding voltage and corresponding losses; I 01 The no-load characteristic curve is on the same as I 0N Another point of equal value; I 0N Rated voltage U N The corresponding rated no-load current; U N Rated voltage; U 02 P 02 'These are the points where the current is minimum, I 0min The corresponding voltage and the corresponding loss.

[0021] Furthermore, step S4 specifically includes the following steps:

[0022] S41. Conduct no-load characteristic tests;

[0023] S42. Perform data processing;

[0024] P0' = P0 - P Cu0 =P Fe +P fw +P s0 (1)

[0025] P Cu0 =1.5×I 2 R

[0026]

[0027] Where P0' is the sum of iron loss and mechanical loss; P0 is the no-load input power; P Cu0 For no-load copper loss; P Fe Iron loss; P fw For mechanical losses; P s0 R represents the stray load loss under no-load conditions; I represents the line current; R represents the DC resistance; R1 and θ1 represent the stator winding resistance and temperature during the no-load characteristic test, respectively; R0 and θ0 represent the initial stator resistance and corresponding temperature in the cold state, respectively.

[0028] S43. Perform curve fitting on the no-load current I0, P0', and no-load voltage U0; find the corresponding I under the weak magnetic state. 01 =I 0N The voltage U corresponding to time 01 and the corresponding loss P 01 ';

[0029]

[0030] P0' N =P FeN +P fw +P s0N (4)

[0031] Among them, I 0N The rated voltage U on the curve N Corresponding rated no-load current, I 01 The no-load characteristic curve is on the same as I 0N The current corresponding to another point of equal value; P FeN P is the iron loss at rated voltage; s0N For the corresponding I 0N No-load stray loss at time; P 0N 'For the corresponding rated voltage U N The sum of iron loss and mechanical loss;

[0032] The iron loss P under rated voltage is obtained by subtracting formula (3) from formula (4). FeN :

[0033]

[0034] Find the point of minimum current I on the I = f(U0) curve. 0min The corresponding voltage U 02 and its corresponding loss P 02 ':

[0035]

[0036] Among them, P s02 The point of minimum current I 0min The corresponding stray loss;

[0037] Mechanical loss P fw :

[0038]

[0039] Furthermore, in step S41, a frequency converter with permanent magnet vector control function is used. By controlling the change of the excitation current provided by the frequency converter to the motor under test, the terminal voltage of the motor under test is increased or decreased to achieve the no-load characteristic test.

[0040] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0041] This invention achieves V / F separation control for starting a permanent magnet synchronous motor by adding an inertia fixture to the rotor of the permanent magnet motor, while avoiding the loss of synchronism in the permanent magnet synchronous motor. It also enables the separate acquisition of iron loss and mechanical loss using the no-load characteristic test of the permanent magnet synchronous motor. It overcomes the high cost problem caused by the use of a dummy rotor in the prior art, and this method can be directly applied to the testing of finished motors, making it highly applicable in engineering. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the test data for the permanent magnet synchronous motor in Example 1. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for separating iron loss and mechanical loss in a variable frequency start permanent magnet synchronous motor, including the following steps:

[0047] S1. Set an inertia fixture on the rotor of the permanent magnet synchronous motor under test to increase the rotor's rotational inertia in order to solve the problem of loss of synchronism when the permanent magnet motor is controlled by a variable frequency power supply; the inertia fixture is a rotating part symmetrical about the central axis; before proceeding to step S2, perform a dynamic balance test on the permanent magnet synchronous motor under test and the inertia fixture.

[0048] In a preferred embodiment, the inertia fixture includes a coupling through which the rotor of the permanent magnet synchronous motor is connected to the rotor of another external motor. The function of this other external motor is not conventional driving, but rather to increase the rotor's rotational inertia while ensuring good dynamic balance.

[0049] S2. Start the permanent magnet synchronous motor by giving voltage and frequency respectively; use a frequency converter to control the operation of the motor under test through its V / F separation control mode.

[0050] S3. Measure the operating parameters of the permanent magnet synchronous motor; the operating parameters include motor voltage, current, power, resistance, temperature and other parameters.

[0051] S4. The iron loss and mechanical loss of the motor are obtained by using the no-load characteristic test method of permanent magnet synchronous motor.

[0052] S41. Conduct no-load characteristic tests;

[0053] S42. Perform data processing;

[0054] P0' = P0 - P Cu0 =P Fe +P fw +P s0 (1)

[0055] P Cu0 =1.5×I 2 R

[0056]

[0057] Where P0' is the sum of iron loss and mechanical loss; P0 is the no-load input power; P Cu0 For no-load copper loss; P Fe Iron loss; P fw For mechanical losses; P s0 R represents the stray load loss under no-load conditions; I represents the line current; R represents the DC resistance; R1 and θ1 represent the stator winding resistance and temperature during the no-load characteristic test, respectively; R0 and θ0 represent the initial stator resistance and corresponding temperature in the cold state, respectively.

[0058] S43. For example Figure 1 As shown, curve fitting is performed on the no-load current I0, P0', and no-load voltage U0, i.e., I0 = f(U0) and P0' = f(U0); the rated voltage U is obtained from the fitted curve. N The corresponding loss P 0N 'and current I 0N According to I 0N Find the value of I corresponding to the weak magnetic state 01 =I 0N The voltage U corresponding to time 01 and the corresponding loss P 01 ';

[0059]

[0060] P0' N =P FeN +P fw +P s0N (4)

[0061] Among them, I 0N The rated voltage U on the curve N Corresponding rated no-load current, I 01 The no-load characteristic curve is on the same as I 0N The current corresponding to another point of equal value; P FeN P is the iron loss at rated voltage; s0N For the corresponding I 0N No-load stray loss at time; P 0N 'For the corresponding rated voltage U N The sum of iron loss and mechanical loss;

[0062] The iron loss P under rated voltage is obtained by subtracting formula (3) from formula (4). FeN :

[0063]

[0064] Find the point of minimum current I on the I = f(U0) curve. 0min The corresponding voltage U 02 and its corresponding loss P 02 ':

[0065]

[0066] Because the speed of a permanent magnet synchronous motor remains constant without losing steps, therefore P fw It is constant under any voltage, and because the current is small at the minimum current point, its corresponding stray loss can be almost ignored, i.e., P s02 =0; obtain mechanical loss P fw :

[0067]

[0068] It is understandable that, in addition to the methods mentioned above, a frequency converter with permanent magnet vector control function can also be used. By controlling the change of the excitation current provided by the frequency converter to the motor under test, the terminal voltage of the motor under test can be increased or decreased to achieve the no-load characteristic test.

[0069] Compared with the prior art, the method of this embodiment solves the problem of V / F separation starting control of permanent magnet synchronous motors without starting windings, enabling variable frequency starting permanent magnet synchronous motors to achieve voltage rise and fall control at a certain fixed frequency; it eliminates the need to manufacture dummy rotors, resulting in lower costs, higher efficiency and convenience, and can be directly applied to finished motor testing, making it more suitable for engineering applications.

[0070] Obviously, the above embodiments are merely examples to clearly illustrate the technical solutions of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for separating iron loss and mechanical loss of a variable frequency starting permanent magnet synchronous motor, characterized in that, The method comprises the steps of: S1. increasing the moment of inertia of the rotor of the permanent magnet synchronous motor to be tested; the moment of inertia of the rotor is increased by setting an inertia tool on the rotor of the permanent magnet synchronous motor to be tested; the tool is a rotation member symmetrical about a central axis; S2. starting the permanent magnet synchronous motor by setting the voltage and frequency respectively; a variable frequency power supply is used to control the operation of the motor to be tested by V / F separation control mode; S3. measuring the operating parameters of the permanent magnet synchronous motor; S4. obtaining the iron loss and mechanical loss of the motor by using the no-load characteristic test method of the permanent magnet synchronous motor.

2. The method of claim 1, wherein, The inertia tool comprises a shaft coupling, and the rotor of the permanent magnet synchronous motor is connected to the rotor of another motor through the shaft coupling.

3. The method of claim 1, wherein, Before the step S2, dynamic balance test is performed on the permanent magnet synchronous motor to be tested and the inertia tool.

4. The method of claim 1, wherein, In the step S3, the operating parameters include motor voltage, current, power, resistance and temperature.

5. The method of claim 1 to 4, wherein, In the step S4, the iron loss P at the time of the rated voltage of the motor is calculated according to the formula (5) FeN ; the mechanical loss P of the motor is calculated according to the formula (7) fw ; （5）; （7）; wherein P 0N is the sum of iron loss and mechanical loss corresponding to rated voltage U N , obtained from the no-load characteristic curve; U 01 , P 01 ' are respectively the voltage and the corresponding loss corresponding to I 01 = I 0N , obtained from the no-load characteristic curve; I 01 is another point on the no-load characteristic curve equivalent to I 0N ; I 0N is the rated no-load current corresponding to rated voltage U N ; U N is the rated voltage; U 02 , P 02 ' are respectively the voltage and the corresponding loss corresponding to the minimum current I 0min .

6. The method of claim 1 to 4, wherein, The step S4 specifically comprises the steps of S41. performing no-load characteristic test; S42. performing data processing; （1）; （2）; wherein P0' is the sum of iron loss and mechanical loss; P0 is the no-load input power; P Cu0 is the no-load copper loss; P Fe is the iron loss; P fw is the mechanical loss; P s0 is the load stray loss under no-load; I is the line current; R is the DC resistance; R1, θ1 are the stator winding resistance value and temperature value at the time of no-load characteristic test; R0, θ0 are the cold initial stator resistance and the corresponding temperature, respectively; S43. Curve fitting is made for the no-load current I0, P0', no-load voltage U0; find the voltage U corresponding to I 01 =I 0N when the field weakening state is reached and the corresponding loss P 01 and P 01 '; （3）; （4）; where I 0N is the rated voltage U N corresponds to the rated no-load current I 01 is the current corresponding to another point on the no-load characteristic curve which is equivalent to I 0N P FeN is the iron loss at rated voltage; P s0N is the no-load stray loss corresponding to I 0N P 0N ' is the sum of the iron loss and the mechanical loss corresponding to the rated voltage U N P The iron loss P at rated voltage is obtained by subtracting equation (3) from equation (4) FeN : （5）; Find the minimum point of current I from the curve I = f(U0) 0min the corresponding voltage U 02 and its corresponding loss P 02 ': （6）; wherein P s02 is the point of minimum current I 0min corresponding to the stray loss; Obtaining mechanical losses P fw : （7）。 7. The method of claim 1, wherein, In the step S4, a frequency converter with permanent magnet vector control function is used to increase or decrease the terminal voltage of the motor to be tested by controlling the change of the excitation current provided by the frequency converter, so as to realize the no-load characteristic test.

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