TW201425963A - Method for measuring iron loss of a permanent-magnet motor and apparatus thereof - Google Patents

Abstract

A method for measuring iron loss of a permanent-magnet motor and apparatus thereof is disclosed. A primary motor is coupled to a passive motor through a coupling, where the motor characteristics of the primary motor are known. A voltage is applied for driving the primary motor to rotate, and the rotation of the primary motor drives the rotor of the passive motor to rotate simultaneously. On the basis of the relationship between the rotational speed of the primary motor and time, a processing unit calculates the time constant of the primary motor. The processing unit then derives the moment of inertia of the primary motor according to the time constant, and uses the moment of inertia to compute the output power of the primary motor. By subtracting the output power from the nominal power of the primary motor under no-load circumstance, the iron loss of the passive motor is derived.

Description

Permanent magnet motor core loss measuring method and device thereof

The invention relates to a method for measuring the loss of a permanent magnet motor core, in particular to a method for measuring the loss of a permanent magnet motor core for measuring the iron loss of a motor.

With the vigorous development of the motor and machinery industry, motor machinery such as motors, generators and transformers can be seen everywhere in life, and due to the environmental awareness of energy saving and carbon reduction in recent years, how to improve the performance of the above-mentioned motor machinery to achieve green energy It has become the primary goal of the academic community and the industry. Among them, because the motor has the widest application range, no matter whether it is used in home appliances, vehicles, 3C products or factory tools, the relevant personnel are all looking for ways to improve the efficiency of the motor.

The main sources of motor efficiency loss can be roughly divided into conductor copper loss, magnet loss and other mechanical losses. Among them, the loss of the magnet (Iron Loss) is the energy loss caused by the motor during operation, including the hysteresis loss caused by the hysteresis effect of the magnetic conductive material, and the magnetic field exchange due to the magnetic field alternating The resulting eddy current loss (Eddy Loss). In the motor construction, a large amount of magnetically permeable material is required for both the stator and the rotor, and the yttrium-containing electromagnetic steel sheet having excellent electromagnetic properties such as high magnetic permeability and high saturation magnetic flux density is used the most, and is usually used. Made into the core part of the motor. Therefore, how to master the characteristics of silicon steel sheet is the necessary information to improve the efficiency of the motor during motor development and production.

Generally, the steel sheet used for the motor core is supplied by the material supplier. The electromagnetic properties and iron loss data of the electromagnetic steel sheet material used in the silicon steel sheet can be tested for the iron loss of the silicon steel sheet by using the Epstein iron loss tester. However, due to the difference in structure and operation of the permanent magnet motors of different designs, the internal magnetic flux density distribution is uneven and may be saturated, thus causing the actual iron loss of the motor and the information provided by the material supplier. There is a considerable gap in the iron loss value of the tested conversion. Furthermore, the magnetically permeable materials used in motors must be processed, shaped, and assembled to become actual motor components, and these procedures can affect the properties of the material. Therefore, it is obviously not enough to estimate the motor iron loss by using only the electromagnetic properties of the material and the iron loss data. It is necessary to actually measure the iron loss between the stator and the rotor after the motor assembly is completed.

The conventional motor iron loss measurement method has the application of the Epstein test principle to the actual motor core measurement. However, this method is accurate and reliable because the actual magnetic flux density and magnetic field strength of the motor core must be detected. Under the consideration of the degree, it is necessary to use a large number of computer simulation analysis operations, which will make the test program and the required instrument become quite complicated, and the defects of extremely poor convenience and high cost are rarely used.

Some scholars have proposed to measure the temperature change around the motor core to estimate the iron loss. The heat balance power method is mainly used to obtain the motor loss, that is, a pipe is connected to a motor to be tested in an incubator. The line changes the temperature difference and flow rate of a heat conductor to estimate the motor loss power. However, this method also has the disadvantage of being too complicated for the measurement procedure, and the heat loss of the motor and the incubator is required to estimate the iron loss, so that the measurement takes too long.

Another method for measuring the iron loss of a motor is made by an active motor. The torque detector is coupled to a motor to be tested, and the motor is driven to rotate by the active motor. By measuring the torque change of the active motor after connecting the motor to be tested at a specific speed, the waiting is estimated. Measure the motor loss power. However, due to the measurement error of the torque detector itself, it will directly lead to an error in the estimated iron loss value of the motor to be tested.

The above-mentioned conventional motor iron loss measurement method has many disadvantages such as insufficient convenience, high cost, long measurement time, and easy error, and therefore it is necessary to provide a further improved permanent magnet motor core loss. Test method.

The object of the present invention is to improve the above disadvantages, and to provide a permanent magnet motor core loss measuring method and device thereof, the permanent magnet motor core loss measuring method and device thereof can actually measure the iron loss of a permanent magnet motor, And without the need for complicated measurement procedures and a large number of computer calculations, it can achieve the effect of measuring the iron loss of the motor to be tested quickly, simply and conveniently.

The second object of the present invention is to provide a permanent magnet motor core loss measuring method and a device thereof, and the method and device for measuring the core loss of the permanent magnet motor do not need to be provided with a torque detector, that is, an active motor coupling Taking the motor to be tested to measure the iron loss of the motor to be tested has the effect of improving the accuracy of the measurement.

A method for measuring the loss of a permanent magnet motor core includes coupling a motor to be tested through a coupling with a known motor characteristic, and actuating the active motor by a certain voltage value to drive the test Rotating the rotor of the motor, and measuring the relationship between the speed of the active motor and the time; and calculating the active horse by the relationship between the speed of the active motor and the time by a processing unit A time constant of the motor to be tested is coupled to the time constant, and the moment of inertia of the motor coupled to the motor to be tested is derived according to the time constant, and the motor is coupled to the motor to be tested by the moment of inertia operation The output power of the time, the output power is subtracted from the output power of the active motor at no load to calculate the rotational iron loss of the motor to be tested.

A permanent magnet motor core loss measuring device comprises a processing unit coupled to a voltage source and a sensing unit, wherein the voltage source has an output terminal for outputting an output voltage, and the sensing unit has a sensing end Supplying the motor speed information; an active motor coupled to the output end and the sensing end respectively to receive the output voltage of the voltage source, and for the sensing unit to measure the rotational speed of the active motor, the active motor The utility model has an output shaft, and a coupling has a first end connected to the output shaft of the driving motor, and a second end connected to the output shaft of the motor to be tested.

The permanent magnet motor core loss measuring method and device thereof, wherein the permanent magnet motor core loss measuring method further comprises a step of measuring a motor characteristic of the active motor, the motor characteristic comprising the permanent magnet motor The moment of inertia at the time of loading, and the relationship between the rotational speed of the active motor and the time when the active motor is idling.

The method and apparatus for measuring the loss of a permanent magnet motor core according to the present invention, wherein the method of estimating the moment of inertia when the driving motor is coupled to the motor to be tested according to the time constant is as follows: τ/τ' = J /J', where τ ' is the time constant when the active motor is coupled to the motor to be tested, J' is the moment of inertia when the active motor is coupled to the motor to be tested, and τ is the moment of inertia when the active motor is unloaded The time constant driven by the constant voltage value, J is the moment of inertia of the active motor at no load.

The permanent magnet motor core loss measuring method and device thereof, wherein the output power of the active motor is calculated by differentiating the relationship between the rotational speed of the active motor and the time to generate an angular acceleration of the active motor, the angle The acceleration multiplied by the moment of inertia of the active motor is the output power of the active motor.

The permanent magnet motor core loss measuring method and device thereof, wherein the method for calculating the time constant of the active motor takes the steady state speed of the active motor, and estimates that the speed of the active motor reaches the steady state during the starting process The time taken for 0.632 times the rotational speed is taken as the time constant.

The method and apparatus for measuring the loss of a permanent magnet motor core according to the present invention, wherein the voltage source is a controllable voltage source, and the processing unit controls an output voltage value of the voltage source.

The permanent magnet motor core loss measuring method and device thereof, wherein the permanent magnet motor core loss measuring device further comprises an incubator disposed adjacent to the second end of the coupling and having a The accommodating space is for accommodating the motor to be tested.

The permanent magnet motor core loss measuring method and device thereof according to the present invention, wherein the permanent magnet motor core loss measuring device further comprises a heat dissipating device disposed around the active motor.

The permanent magnet motor core loss measuring method and device thereof are the coreless brushless motor.

The above and other objects, features and advantages of the present invention will become more apparent. BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which are illustrated as follows: Referring to Figures 1 and 2, the permanent magnet motor core loss measurement of the present invention is shown. A first embodiment of a method and apparatus therefor. The permanent magnet motor core loss measuring device comprises a voltage source 1, a sensing unit 2, a processing unit 3, an active motor 4, a coupling 5 and a motor 6 to be tested. The voltage source 1 has a controlled terminal 11 and a voltage output terminal 12. The sensing unit 2 has an information output terminal 21 and a sensing terminal 22, and the processing unit 3 is coupled to the voltage source 1 respectively. The terminal 11 and the information output terminal 21 of the sensing unit 2 are respectively coupled to the voltage output terminal 12 of the voltage source 1 and the sensing terminal 22 of the sensing unit 2. In addition, the driving motor 4 has an output shaft 41 connected to a coupling 5, which is further connected to an output shaft 61 of a motor 6 to be tested.

The voltage source 1 is a controllable voltage source that outputs an output voltage through its voltage output terminal 12 to drive the active motor 4 to operate. The sensing unit 2 is a conventional speed measuring device. The sensing end 22 senses the rotational speed information of the active motor 4, and preferably senses the current information of the active motor 4. The processing unit 3 can control the output voltage value of the voltage source 1 by using the controlled terminal 11 of the voltage source 1 , and receive the speed information and current sensed by the sensing unit 2 by the information output end 21 of the sensing unit 2 . News. The active motor 4 is preferably a coreless brushless motor in the present embodiment based on the high speed demand and the reduced measurement error, but the invention is not limited thereto. The two ends of the coupling 5 are respectively connected to the output shaft 41 of the driving motor 4 and the output shaft 61 of the motor 6 to be tested, so that the driving motor 6 can be synchronously driven to rotate when the driving motor 4 is in operation. The motor 6 to be tested is a permanent magnet motor. When rotating, a rotating iron loss is generated between the rotor and the stator, which is the measurement target of the present invention.

The permanent magnet motor core loss measuring device according to the first embodiment of the present invention operates to perform the operation process of the permanent magnet motor core loss measuring method of the present invention, as described in detail later. Referring to FIGS. 1 and 2 together, first, the motor characteristic of the driving motor 4 is measured. The motor characteristic means that the driving motor 4 includes the driving motor 4 under the condition of no load (no load is mounted). Moment of inertia J (Moment of Inertia, J), and a certain voltage value V is applied to the active motor 4 in a stationary state, so that it starts to rotate from a stationary state and the rotational speed is gradually increased to a steady-state rotational speed S. In the process, the speed of the active motor 4 is related to time. The physical meaning of the motor characteristic is detailed below, which can be derived from the Newtonian equation of motion. For a motor, the torque is the product of the moment of inertia J and the angular acceleration, as shown in the following equation (1): T = J × α (1) where T is the torque of the motor and α is the angular acceleration of the motor. If a certain voltage value V is applied to a motor, the motor will start to rotate from a stationary state and the rotational speed is gradually increased to a steady-state rotational speed S. In the process from the start of the motor to the steady-state rotational speed S, the relationship between the rotational speed and time is as follows Equation (2): ω ( t ) = S (1 ^- e ^{- t / τ} ) (2) where ω ( t ) is the rotational speed of the motor at a time t, and τ is the time constant of the motor The time constant τ is defined as the time required for the rotational speed to reach 0.632 times the steady-state rotational speed S during the starting of the motor. Please refer to FIG. 3 for the relationship between the rotational speed of the motor and time. Further, it is known that the time constant τ is proportional to the moment of inertia J and the line resistance of the motor, and inversely proportional to the square of the torque constant of the motor, as shown in the following equation (3): Where R is the line resistance of the motor, K _{T is} the torque constant of the motor, and it is known that a line resistance R and a torque constant K _T are constant values regardless of whether or not the motor is attached to the load.

The relationship between the rotational speed of the motor and the time (2) is differentiated, and the angular acceleration of the motor is obtained as a function of time, as shown in the following equation (4): Where α ( t ) is the angular acceleration of the motor at time t. Therefore, it can be inferred from the above formula (2) and the above formula (4) that if the motor has the rotational speed ω ( t ) at a time t as the axial value of the X-axis, and the motor The angular acceleration α ( t ) at this time t is taken as the axial value of the Y-axis, and the relationship between the rotational speed ω and the angular acceleration α as shown in Fig. 4 can be plotted, which is in a straight line relationship. And the equation of the straight line is as shown in the following formula (5): Wherein, when the rotational speed ω is zero, the angular acceleration α reaches a maximum value, which is equal to the steady-state rotational speed S divided by the time constant τ ; when the rotational speed ω reaches a maximum value, which is equal to the steady-state rotational speed S, The angular acceleration α is zero.

In addition, according to the above formula (1), after the angular acceleration α of the motor is multiplied by the moment of inertia J, the output torque T of the motor is obtained; and, the rotational speed ω of the motor is corresponding to the rotational speed ω . The output torque T is multiplied to obtain the output power P of the motor. The relationship between the output torque T and the output power P is as shown in Fig. 5, wherein T ( ω ) is the output torque T of the motor at a rotational speed ω , P ( ω ) is the motor The output power P at a rotational speed ω .

Since the moment of inertia J is a certain value when the driving motor 4 is idling, and the driving motor 4 receives the constant voltage value V, the relationship between the rotational speed ω and the time t is also fixed, so the active motor 4 is measured. The step of the motor characteristic only needs to be performed once when the active motor 4 is used for the first time, and this step can be omitted when the active motor 4 is used again for measurement.

After the motor characteristics of the driving motor 4 are known, the output shaft 41 of the driving motor 4 and the output shaft 61 of the motor to be tested 6 are respectively connected to the two ends of the coupling 5, and the voltage is controlled by the control unit 1. The source 1 applies the constant voltage value V to the driving motor 4 to start the operation of the driving motor 4 to synchronously drive the motor 6 to be tested to rotate. At the same time, the sensing end 21 of the sensing unit 2 measures the relationship between the rotational speed of the driving motor 4 and the time when the driving motor 6 rotates the driving motor 6 to be tested.

Referring to FIG. 6, the measurement result of the sensing unit 2 in the above step is combined with the motor characteristic of the driving motor 4, wherein ω ( t ) is the rotational speed of the motor characteristic of the driving motor 4 . In relation to time, ω'(t) is a relationship between the rotational speed of the active motor 4 and the time when the driving motor 6 rotates by the driving motor 4. As shown in the figure, after the coupling motor 5 is coupled to the motor 6 to be tested through the coupling 5, the steady-state rotational speed S′ that can be achieved when the same constant voltage value V is received is compared with the active motor. 4 The steady-state speed S at no load will be reduced. In addition, the time constant τ ' after the driving motor 4 is coupled to the motor 6 to be tested is increased compared with the time constant τ when the driving motor 4 is idling. The time constant τ ' is the time required for the rotational speed of the active motor 4 to be coupled to the motor 6 to be tested to reach 0.632 times the steady-state rotational speed S′ during the starting process.

The processing unit 3 receives the measurement result of the sensing unit 2, and performs an iron loss analysis operation of the motor 6 to be tested according to the following, and the iron loss analysis operation manner is as follows. Since the moment of inertia J' after the driving motor 4 is coupled to the motor 6 to be tested is increased by a moment of inertia J greater than the motor characteristic of the driving motor 4, the driving motor 4 will be operated when receiving the same constant voltage value V. The steady state speed S' that can be achieved is reduced. As shown in the above formula (3), the time constant τ of the driving motor 4 is proportional to the moment of inertia J and the line resistance R of the motor, and inversely proportional to the square of the torque constant K _T of the driving motor 4, however The line resistance R and the torque constant number K _{T of} the driving motor 4 are not affected by the load. Therefore, the time constant of the driving motor 4 before and after the motor 4 to be tested is changed, and the moment of inertia of the driving motor 4 is changed. In the following equation (6): τ/τ' = J/J' (6) According to this, the processing unit 3 is coupled to the time constant τ ' after the driving motor 6 is coupled to the motor 6 to be tested, and The moment of inertia J and the time constant τ of the motor characteristic of the driving motor 4 can be calculated to generate the moment of inertia J' after the driving motor 4 is coupled to the motor 6 to be tested.

Knowing the moment of inertia J' after the driving motor 4 is coupled to the motor 6 to be tested, and the relationship between the rotational speed of the driving motor 4 and the time when the driving motor 6 drives the motor 4 to be tested to rotate ω'(t) According to the foregoing steps, the relationship between the output torque T' of the driving motor 4 and the output power P' can be plotted, and the relationship between the output torque T and the output power P when the driving motor 4 is idling is compared. Figure, as shown in Figure 7. Where T ( ω ) is the output torque T at a rotational speed ω when the active motor 4 is idling, P ( ω ) is the output power P at a rotational speed ω when the active motor 4 is idling; T' ( ω) when the driving motor 4 drives the motor 6 to be tested to rotate, the output torque T′ at a rotational speed ω , and P′(ω) is when the driving motor 4 drives the motor 6 to be tested to rotate. Output power P' at speed ω .

When the motor 6 to be tested is rotated by the driving motor 4 and rotated at a rotation speed ω , the power loss P _L ( ω ) caused by the motor 6 to be tested is calculated by the following formula (7): P _L ( ω) = P(ω) - P'(ω) (7) Please refer to Fig. 8 for the relationship between the power loss P _L and the rotational speed ω caused by the motor 6 to be tested. If the friction loss of the motor is neglected, the power loss P _{L is} the rotational iron loss between the rotor and the stator of the motor 6 to be tested, which is the result of the invention.

Since the processing unit 3 can adjust its output voltage through the controlled terminal 11 of the voltage source 1 to drive the driving motor 4 to operate in different speed ranges, the permanent magnet motor core loss measuring method and device thereof according to the present invention The rotating iron loss of the motor to be tested in different speed ranges can be measured. In addition, the processing unit 3 receives the current information of the active motor 4 sensed by the sensing end 21 of the sensing unit 2, and outputs the output voltage to the active motor 4 according to the voltage source 1 for monitoring the active motor 4 Operational status to confirm the correctness of the measurement results.

Referring to FIG. 9, a system architecture diagram of a second embodiment of a permanent magnet motor core loss measuring method and apparatus thereof according to the present invention is shown. With the first The difference between the embodiments is that the permanent magnet motor core loss measuring method of the present invention further comprises an incubator 7 and a heat sink 8. The incubator 7 is disposed adjacent to the coupling 5 and has an accommodating space. The motor 6 to be tested is disposed in the accommodating space, and the output shaft 61 of the motor 6 to be tested protrudes from the incubator 7 To connect the coupling 5 . The incubator 7 provides different constant temperature conditions for measuring the iron loss of the motor 6 to be tested at different temperatures. The heat dissipating device 8 is coupled to the processing unit 3 and disposed at the periphery of the driving motor 4, and has a cooling and cooling effect to improve the measurement stability of the driving motor 4, thereby preventing the driving motor 4 from being rotated during the measuring process. The temperature rises, which in turn affects the accuracy of the measurement results.

In summary, the method and device for measuring the loss of the permanent magnet motor core of the present invention only need to select a driving motor with a known characteristic, and measure the rotation speed of the driving motor to drive the motor to be tested. A processing unit calculates the iron loss of the motor to be tested, and does not require complicated measurement procedures and a large number of computer operations, and can achieve the effect of measuring the iron loss of the motor to be tested quickly, simply and conveniently.

The permanent magnet motor core loss measuring method and device thereof are characterized in that an active motor is coupled to a motor to be tested through a coupling, and the active motor is measured when the driving motor drives the motor to be tested to rotate. The speed can measure the iron loss of the motor to be tested, and the torque detector is not needed, which can avoid the measurement error of the torque detector and affect the iron loss measurement result, and has the effect of improving the measurement accuracy.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

〔this invention〕

1‧‧‧voltage source

11‧‧‧ controlled end

12‧‧‧Voltage output

2‧‧‧Sensor unit

21‧‧‧Information output

22‧‧‧Sense end

3‧‧‧Processing unit

4‧‧‧Active motor

41‧‧‧ Output shaft

5‧‧‧Coupling

6‧‧‧Motor to be tested

61‧‧‧ Output shaft

7‧‧‧ incubator

8‧‧‧heating device

ω ‧‧‧ rpm

t‧‧‧Time

τ ‧‧ ‧ time constant

S‧‧‧steady speed

α ‧‧‧ angular acceleration

J‧‧‧ moment of inertia

V‧‧‧ constant voltage value

T‧‧‧ output torque

P‧‧‧output power

P _L ‧‧‧Power loss

R‧‧‧Wire resistance

K _T ‧‧‧Torque constant

Fig. 1 is a system architecture diagram of a first embodiment of a permanent magnet motor core loss measuring method and apparatus therefor.

Fig. 2 is a flow chart showing the operation of the first embodiment of the permanent magnet motor core loss measuring method and apparatus of the present invention.

Fig. 3 is a graph showing the relationship between the rotational speed and the time of the active motor at the time of no-load of the first embodiment of the permanent magnet motor core loss measuring method of the present invention.

Fig. 4 is a view showing the relationship between the rotational speed and the angular acceleration of the active motor at the time of no-load of the first embodiment of the permanent magnet motor core loss measuring method of the present invention.

Fig. 5 is a graph showing the relationship between the output torque and the output power of the active motor at no load in the first embodiment of the permanent magnet motor core loss measuring method of the present invention.

Fig. 6 is a view showing the relationship between the relationship between the rotational speed and the time when the active motor coupled to receive the motor is measured and the relationship between the rotational speed and the time of the active motor at no load in the first embodiment of the method for measuring the loss of the core of the permanent magnet motor of the present invention; .

Fig. 7 is a view showing the output torque and the output power of the active motor coupled to the motor and the output torque and the output power at the time of no-load when the active motor is coupled to the motor according to the first embodiment of the present invention Comparison chart.

Fig. 8 is a graph showing the relationship between the power loss and the rotational speed caused by the motor to be tested in the first embodiment of the permanent magnet motor core loss measuring method of the present invention.

Figure 9: Method and device for measuring the loss of the core of the permanent magnet motor of the present invention System architecture diagram of the second embodiment.

1‧‧‧voltage source

11‧‧‧ controlled end

12‧‧‧Voltage output

2‧‧‧Sensor unit

21‧‧‧Information output

22‧‧‧Sense end

3‧‧‧Processing unit

4‧‧‧Active motor

41‧‧‧ Output shaft

5‧‧‧Coupling

6‧‧‧Motor to be tested

61‧‧‧ Output shaft

Claims (10)

A permanent magnet motor core loss measuring method includes: coupling a motor to be tested through a coupling through a coupling motor of a known motor characteristic, and actuating the active motor by a certain voltage value to drive the standby motor Measuring the rotation of the motor, measuring the relationship between the speed of the active motor and the time; and calculating the time constant of the active motor coupled to the motor to be tested by a processing unit from the relationship between the speed of the active motor and the time, and The time constant derives the moment of inertia when the driving motor is coupled to the motor to be tested, and the output power of the driving motor when the driving motor is coupled to the motor to be tested is generated by the moment of inertia operation, and the output power is subtracted from the driving motor. The output power at no load is used to calculate the rotational iron loss of the motor to be tested. The permanent magnet motor core loss measuring method according to claim 1, wherein the permanent magnet motor core loss measuring method further comprises a step of measuring a motor characteristic of the driving motor, the motor characteristic including the The moment of inertia of the permanent magnet motor at no load, and the relationship between the speed and time at which the active motor is driven by the constant voltage. The method for measuring the loss of a permanent magnet motor core according to claim 1 or 2, wherein the method of estimating the moment of inertia when the driving motor is coupled to the motor to be tested according to the time constant is as follows: τ/τ' = J/J', where τ ' is the time constant of the active motor coupled to the motor to be tested, J' is the moment of inertia when the active motor is coupled to the motor to be tested, and τ is the active motor The moment of inertia when no-load is driven by the constant voltage value, and J is the moment of inertia of the active motor at no load. According to the method for measuring the loss of the permanent magnet motor core according to claim 1 or 2, wherein the process of generating the output power of the active motor is to differentiate the relationship between the rotational speed of the active motor and the time to generate the active The angular acceleration of the motor is multiplied by the moment of inertia of the active motor as the output power of the active motor. According to the method for measuring the loss of the permanent magnet motor core according to claim 1 or 2, wherein the time constant of the active motor is calculated by taking the steady-state rotational speed of the active motor, and estimating the active motor during the starting process. The time taken for the medium speed to reach 0.632 times the steady state speed is taken as the time constant. A permanent magnet motor core loss measuring device comprises: a processing unit coupled to a voltage source and a sensing unit, the voltage source having an output terminal for outputting an output voltage, the sensing unit having a sensing The end motor supplies the motor speed information; an active motor is coupled to the output end and the sensing end respectively to receive the output voltage of the voltage source, and the sensing unit measures the rotation speed of the active motor, the active motor The other has an output shaft; and a coupling has a first end and a second end, the first end is connected to the output shaft of the driving motor, and the second end is connected to the output shaft of the motor to be tested. The permanent magnet motor core loss measuring device according to claim 6, wherein the voltage source is a controllable voltage source, and the processing unit controls an output voltage value of the voltage source. The permanent magnet motor core loss measuring device according to claim 6, wherein the permanent magnet motor core loss measuring device further comprises a constant temperature The box is disposed adjacent to the second end of the coupling and has an accommodating space for accommodating the motor to be tested. The permanent magnet motor core loss measuring device according to claim 6, wherein the permanent magnet motor core loss measuring device further comprises a heat dissipating device disposed around the active motor. The permanent magnet motor core loss measuring device according to claim 6, wherein the active motor is a coreless brushless motor.