A high overload pulse type motor torque loading system and method

Abstract

The invention discloses a high overload pulse type motor torque loading system, including a torque loading device, a torque measuring device and a timing device; the torque loading device includes a synchronous generator, a motor to be tested, a variable resistor, a rectifier bridge, a coupling No. 1 and a coupling No. 2; the motor to be tested is connected to the synchronous generator through two couplings; the synchronous generator is connected to the AC side of the rectifier bridge, and the DC side of the rectifier bridge is connected in series with a variable resistor and a timing device to form a torque loading loop; when the timing device works within the peak torque holding time or the load torque holding time, the torque loading loop is closed or disconnected, and the motor to be tested bears the peak load torque or the small load torque. The invention can provide a large load that can be adjusted with high precision for the motor, the loading time can be accurately controlled, the torque response time is extremely short, and the dynamic pulse type loading of the motor is realized, the efficiency of the motor load test is improved, and the reliability of the motor test is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of motor testing, and in particular relates to a motor torque loading system and method. Background Art

[0002] In the field of bipedal robots, electric motors are core components that provide power for various mechanisms of the robot. Bipedal robots are similar to humans, with multiple degrees of freedom in their joints, and the working mode of the joint drive motors is a pulsed high-overload operation. Taking the leg joint movement of a bipedal robot as an example, when the robot lifts its legs, the knee joint motor operates at an overload state of more than 10 times the rated torque; when the robot jumps, the legs require a lot of force, forcing the drive motors of each joint to provide peak torque as the driving force, that is, the joint drive motors need to frequently output peak torque. Therefore, the performance test of the bipedal robot drive motor is very important, and the overload performance of the motor is generally tested by applying continuous instantaneous peak torque to the motor.

[0003] In the prior art, Chinese patent CN108107359A proposes "a torque loading device for electromagnetic compatibility test of electric motor system". The invention proposes a torque loading device for electric motor, which uses an oil pump connected to the motor shaft through a reduction device. This structure is relatively bulky, requires a large working space, and the oil pump pressure control is complicated, making it difficult to achieve precise control of the motor torque; moreover, affected by the displacement of the hydraulic oil pump, when the motor speed is low, it cannot meet the working requirements of the device. Therefore, the invention patent has low practicality and is not easy to implement.

[0004] Chinese patent CN110715809A proposes "a loading system and method for a small motor for a vehicle". The invention proposes a loading system and method for a small motor. The loading system includes a motor mounting device and a loading device. The loading device includes a loading stand, a friction plate rotatably connected to the loading stand, a coupling for connecting the friction plate and the motor, and a resistance loading mechanism installed on the loading stand and used to load the friction plate with rotational resistance. This structure manually adjusts the four pressure adjustment buttons of the loading device so that the four pressure gauges show the same reading before the motor under test can be driven to complete the loading. The operation process is complicated, and it is difficult to control the pressure values ​​of the four pressure gauges to be consistent during the loading process; only continuous loading can be achieved, and impact loading cannot be performed; after the loading time is over, the load cannot be removed immediately. Therefore, the possibility of widespread use of this invention is low.

[0005] The use of a synchronous generator connected to a resistive load device to simulate a load is convenient to operate, simple in structure, and low in cost. It is suitable for long-term loading tests. By adjusting the resistance of the load device to change the torque, dynamic loading can be achieved. However, this loading method can only achieve long-term continuous loading, the loading time is uncontrollable, and the motor cannot be impact-loaded; due to the continuous loading time, when the motor is heavily loaded, the motor generates a lot of heat, and it is difficult to remove the heavy load in time by adjusting the resistance, which can easily burn the motor. Therefore, the motor peak torque performance test cannot be performed, and improvements need to be made to this loading method. Summary of the invention

[0006] In order to overcome the deficiencies of the prior art, the present invention provides a high overload pulse type motor torque loading system, including a torque loading device, a torque measuring device and a timing device; the torque loading device includes a synchronous generator, a motor to be tested, a variable resistor, a rectifier bridge, a coupling No. 1, and a coupling No. 2; the motor to be tested is connected to the synchronous generator through two couplings; the synchronous generator is connected to the AC side of the rectifier bridge, and the DC side of the rectifier bridge is connected in series with a variable resistor and a timing device to form a torque loading circuit; when the timing device works within the peak torque holding time or the load torque holding time, the torque loading circuit is closed or disconnected, and the motor to be tested is subjected to the peak load torque or the small load torque. The present invention can provide a large load that can be adjusted with high precision for the motor, the loading time can be accurately controlled, the torque response time is extremely short, and the dynamic pulse type loading of the motor is realized, the efficiency of the motor load test is improved, and the reliability of the motor test is increased.

[0007] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0008] A high overload pulse type motor torque loading system, comprising a torque loading device, a torque measuring device and a timing device;

[0009] The torque loading device includes a synchronous generator, a motor to be tested, a variable resistor, a rectifier bridge, a No. 1 coupling, and a No. 2 coupling; the torque measuring device includes a torque speed sensor and a torque speed display;

[0010] The motor under test is connected to one end of the torque and speed sensor through a No. 2 coupling, and the other end of the torque and speed sensor is connected to the synchronous generator through a No. 1 coupling. The torque and speed sensor is used to detect the load torque value loaded on the shaft of the motor under test and the speed value of the motor under test in real time; the armature winding of the synchronous generator is connected to the AC side of the rectifier bridge, and the DC side of the rectifier bridge is connected in series with a variable resistor and a timing device. The armature winding of the synchronous generator, the rectifier bridge, the variable resistor and the timing device constitute a torque loading circuit; the torque and speed display is connected to the electrical interface of the torque and speed sensor, and is used to display the torque and speed sensor detection value in real time; the motor under test drives the synchronous generator to rotate during rotation, and the load torque borne by the motor under test reaches the peak load torque by adjusting the resistance value of the variable resistor;

[0011] The timing device includes a timer, a solid-state relay and a DC voltage-stabilized switching power supply; the two input ends of the timer are respectively connected to the positive and negative electrodes of the DC voltage-stabilized switching power supply, and the two output ends of the timer are respectively connected to the positive and negative terminals of the solid-state relay input end; one end of the solid-state relay load end is connected to the DC side of the rectifier bridge, and the other end of the solid-state relay load end is connected to a variable resistor; the timer is used to set the peak torque holding time and the load torque holding time, and the solid-state relay is turned on and off according to the peak torque holding time and the load torque holding time set by the timer, and the opening and closing of the solid-state relay controls the closing and opening of the torque loading circuit; the DC voltage-stabilized switching power supply supplies power for the timer.

[0012] Furthermore, the timer includes a first display screen, a second display screen, a knob No. 1, a knob No. 2 and a control chip; the control chip is used to write the timing logic of the timer; the knob No. 1 is used to set the peak torque holding time, and the peak torque holding time is displayed through the first display screen; the knob No. 2 is used to set the load torque holding time, and the load torque holding time is displayed through the second display screen; when the timer works within the peak torque holding time, the solid-state relay is turned on, the torque loading circuit is closed, and the motor under test is subjected to the peak load torque; when the timer works within the load torque holding time, the solid-state relay is turned off, the torque loading circuit is disconnected, and the motor under test is subjected to a small load torque.

[0013] Furthermore, the micro load torque refers to a torque with a torque value ≤ 0.1% FS.

[0014] Furthermore, the voltage value of the DC regulated switching power supply is 15VDC.

[0015] A high overload pulse type motor torque loading method comprises the following steps:

[0016] Step 1: Start the motor under test. The motor under test drives the synchronous generator to rotate through the No. 1 coupling and the No. 2 coupling. At this time, the motor under test is subjected to a small load torque.

[0017] Step 2: According to the maximum value of the peak load torque of the motor under test, the speed of the motor under test is increased to a certain value, so that the synchronous generator generates a back electromotive force that matches the maximum value of the peak load torque of the motor under test; and then the resistance value of the variable resistor is adjusted so that the load torque of the motor under test reaches the peak torque of the motor under test;

[0018] Step 3: Start the timer, adjust knob No. 1 and knob No. 2 to set the peak torque holding time and load torque holding time of the timer respectively; when the peak torque holding time start pulse arrives, the solid-state relay is turned on, the torque loading circuit is closed, the synchronous generator generates a reverse torque, the torque value of the motor under test rises to the peak load torque, the motor under test bears the peak load torque until the next load torque holding time start pulse arrives, and the time of the peak load torque applied to the motor under test is the set peak torque holding time; when the load torque holding time start pulse arrives, the torque loading circuit is disconnected, the synchronous generator generates a small load torque, the motor under test bears the small load torque until the next peak torque holding time start pulse arrives, and the time of the small load torque applied to the motor under test is the set load torque holding time; the load torque value loaded on the shaft of the motor under test and the speed value of the motor under test are displayed on the torque and speed display; thereby realizing the pulse-type change of the load torque of the motor under test.

[0019] The high overload pulse motor torque loading system and method of the present invention produce the following beneficial effects:

[0020] 1. The torque loading device of the present invention uses a synchronous generator connected to a resistive load device to simulate the large load required by the motor, and accurately controls the torque applied to the motor under test by changing the resistance value of the variable resistor. At the same time, the torque speed is displayed in real time through the torque speed sensor to realize dynamic adjustment and observation of the torque.

[0021] 2. The present invention adopts a timing device, and the peak torque holding time and the load torque holding time are set by the timer, so the torque loading time can be accurately controlled to realize pulse-type peak torque loading; the motor peak load torque impact test, mechanical property test and motor temperature rise test can be completed, which is very suitable for the testing requirements of some high overload motors such as robot joint drive motors; at the same time, the timer's precise control of the loading time greatly increases the reliability and safety of the motor load test.

[0022] 3. The present invention has high compactness and high sensitivity, the peak load torque of the motor rises and falls quickly, and the system response time is extremely short; the motor to be tested and the synchronous generator are coaxially connected through the sensor, the coaxiality of the axis is high, and there are no other components, so the system error is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0024] Figure 2 It is a circuit schematic diagram of the present invention.

[0025] Figure 3 It is a structural diagram of a timing device of the present invention.

[0026] Figure 4 It is a schematic diagram of peak torque pulse type loading of the present invention.

[0027] In the figure, 1- coupling No. 1, 2- synchronous generator, 3- rectifier bridge, 4- solid-state relay, 5- variable resistor, 6- timer, 7- DC voltage-stabilized switching power supply, 8- motor under test, 9- coupling No. 2, 10- torque and speed sensor, 11- torque and speed display, 12- knob No. 1, 13- knob No. 2. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0029] like Figure 1 and Figure 2 As shown, the present invention provides a high overload pulse type motor torque loading system, including a torque loading device, a torque measuring device and a timing device;

[0030] The torque loading device includes a synchronous generator 2, a motor to be tested 8, a variable resistor 5, a rectifier bridge 3, a first coupling 1, and a second coupling 9; the torque measuring device includes a torque speed sensor 10 and a torque speed display 11;

[0031] The motor 8 under test is connected to one end of a torque speed sensor 10 through a No. 2 coupling 9, and the other end of the torque speed sensor 10 is connected to a synchronous generator 2 through a No. 1 coupling 1. The torque speed sensor 10 is used to detect the load torque value loaded on the shaft of the motor 8 under test and the speed value of the motor 8 under test in real time; the armature winding of the synchronous generator 2 is connected to the AC side of the rectifier bridge 3, and the DC side of the rectifier bridge 3 is connected in series with a variable resistor 5 and a timing device. The armature winding of the synchronous generator 2, the rectifier bridge 3, the variable resistor 5 and the timing device constitute a torque loading circuit; the torque speed display 11 is connected to the electrical interface of the torque speed sensor 10, and is used to display the detection value of the torque speed sensor 10 in real time; the motor 8 under test drives the synchronous generator 2 to rotate during rotation, and by adjusting the resistance value of the variable resistor 5, the load torque borne by the motor 8 under test reaches the peak load torque;

[0032] The timing device includes a timer 6, a solid-state relay 4 and a DC voltage-stabilized switching power supply 7; the two input ends of the timer 6 are respectively connected to the positive and negative electrodes of the DC voltage-stabilized switching power supply 7, and the two output ends of the timer 6 are respectively connected to the positive and negative terminals of the input end of the solid-state relay 4; one end of the load end of the solid-state relay 4 is connected to the DC side of the rectifier bridge 3, and the other end of the load end of the solid-state relay 4 is connected to the variable resistor 5; the timer 6 is used to set the peak torque holding time and the load torque holding time, and the solid-state relay 4 is turned on and off according to the peak torque holding time and the load torque holding time set by the timer 6, and the opening and closing of the solid-state relay 4 controls the closing and opening of the torque loading circuit; the DC voltage-stabilized switching power supply 7 supplies power to the timer 6.

[0033] Furthermore, the timer 6 includes a first display screen, a second display screen, a knob No. 12, a knob No. 2 13 and a control chip; the control chip is used to write the timing logic of the timer 6; the knob No. 12 is used to set the peak torque holding time, and the peak torque holding time is displayed through the first display screen; the knob No. 2 13 is used to set the load torque holding time, and the load torque holding time is displayed through the second display screen; when the timer 6 works within the peak torque holding time, the solid-state relay 4 is turned on, the torque loading circuit is closed, and the motor 8 under test is subjected to the peak load torque; when the timer 6 works within the load torque holding time, the solid-state relay 4 is turned off, the torque loading circuit is disconnected, and the motor 8 under test is subjected to a small load torque.

[0034] A high overload pulse type motor torque loading method comprises the following steps:

[0035] Step 1: Start the motor under test. The motor under test drives the synchronous generator to rotate through the No. 1 coupling and the No. 2 coupling. At this time, the motor under test is subjected to a small load torque.

[0036] Step 2: According to the maximum value of the peak load torque of the motor under test, the speed of the motor under test is increased to a certain value, so that the synchronous generator generates a back electromotive force that matches the maximum value of the peak load torque of the motor under test; and then the resistance value of the variable resistor is adjusted so that the load torque of the motor under test reaches the peak torque of the motor under test;

[0037] Step 3: Start the timer, adjust knob No. 1 and knob No. 2 to set the peak torque holding time and load torque holding time of the timer respectively; when the peak torque holding time start pulse arrives, the solid-state relay is turned on, the torque loading circuit is closed, the synchronous generator generates a reverse torque, the torque value of the motor under test rises to the peak load torque, the motor under test bears the peak load torque until the next load torque holding time start pulse arrives, and the time of the peak load torque applied to the motor under test is the set peak torque holding time; when the load torque holding time start pulse arrives, the torque loading circuit is disconnected, the synchronous generator generates a small load torque, the motor under test bears the small load torque until the next peak torque holding time start pulse arrives, and the time of the small load torque applied to the motor under test is the set load torque holding time; the load torque value loaded on the shaft of the motor under test and the speed value of the motor under test are displayed on the torque and speed display; thereby realizing the pulse-type change of the load torque of the motor under test. Specific embodiment:

[0039] The working principle of the present invention is as follows:

[0040] When a synchronous generator is rotated by the motor under test and has a specified excitation, an induced electromotive force e is generated on the armature winding of the synchronous generator. a (t):

[0041] e a (t) = K e ω(t) (1)

[0042] Where: Ke is the back EMF constant (V / s), ω(t) is the motor speed (radians / s).

[0043] If a variable resistor is connected across the armature winding terminals through a rectifier bridge, a current i will flow between the variable resistor and the armature winding. a (t) flows through, i a (t) is called the loading current:

[0044]

[0045] Where: R a is the armature resistance (ohms), R L is a variable resistor (ohm).

[0046] i a (t) The synchronous generator generates a torque that hinders the rotation of the motor under test.

[0047] M c (t) = K m ×i a (t) (3) Where: K m is the motor torque constant (kg·m / ampere)

[0048] From formulas (1), (2), and (3), we can see that the loading current i a The magnitude of (t) depends on the value of the variable resistor, the reversing torque M c (t) depends on the size of the load current. When the variable resistance decreases, the load current i a (t) increases, the reverse torque M c (t) increases, the load torque applied to the measured motor 8 increases; conversely, the load torque applied to the measured motor decreases. According to the peak torque of the measured motor, the resistance value of the variable resistor is set to ensure that when the measured motor is at a certain speed, the synchronous generator can generate the peak torque that the measured motor can withstand. At this time, a timing device is connected to the torque loading circuit, the timer sets the torque holding time, and the solid-state relay is turned on and off according to the time set by the timer, thereby controlling the on and off of the torque loading device circuit to achieve control of the load torque of the measured motor; when the solid-state relay is turned on, the variable resistor is connected to the circuit, and the synchronous generator provides the peak load torque to the measured motor; when the solid-state relay is off, the torque loading device circuit is disconnected, and the measured motor is subjected to the small load torque brought by the synchronous generator.

[0049] Reference Figure 3The control chip of the timing device is the core component of the timer, which is used to write the timing logic of the timer to ensure accurate timing without error; Knob No. 1 is used to set the peak torque holding time, which is displayed on display 1; Knob No. 2 is used to set the load torque holding time, which is displayed on display 2. The positive and negative terminals of the timer input are connected to the positive and negative terminals of the DC voltage-stabilized switching power supply; the DC voltage-stabilized switching power supply provides a 15VDC working voltage for the timer; the positive and negative terminals of the timer output are connected to the positive and negative terminals of the solid-state relay input to control the solid-state relay to turn on and off; the load end of the solid-state relay is connected to the variable resistor and the rectifier bridge to form a closed loop. The timer can flexibly set the load torque holding time and the load torque holding time. The solid-state relay connected to the timer can be turned on and off according to the timer setting time. The on and off of the solid-state relay determines the opening and closing of the torque loading circuit; when the timer works in the peak torque holding time state, the solid-state relay is immediately turned on, and the opening time is the peak torque holding time. The torque loading circuit is closed, and the motor under test is subjected to the peak load torque after a short torque rise time; when the peak torque holding time ends, the timer immediately works in the load torque holding time state, the solid-state relay is immediately disconnected, and the disconnection time is the load torque holding time. The variable resistor is disconnected, and the torque loading circuit does not work. Then, the torque value borne by the motor under test will drop to the small load torque value brought by the synchronous generator after a short decline time, and continue to run. That is, the opening and closing time of the torque loading circuit can be controlled according to the peak torque holding time pulse and the load torque holding time pulse, so as to realize the pulsed change of the torque of the motor under test from the peak torque to the small load torque. Figure 4 shown.

[0050] Among them, the micro load torque is ≤0.1%FS, and the peak torque rise / fall time is less than or equal to 0.05s.

[0051] The synchronous generator is connected to one side of the torque and speed sensor through coupling No. 1, and the other side of the torque and speed sensor is connected to the motor under test through coupling No. 2. The coaxiality of the two motors is ensured during installation to reduce the load torque error; the armature three-phase winding of the synchronous generator is connected to the AC side of the rectifier bridge through wires, and the rectifier bridge is used to connect the timing device and the variable resistor; the variable resistor is connected to the timing device through wires and connected in series to the DC side of the rectifier bridge to ensure the circuit closure of the timing device. When the timing device is working, the resistance value of the variable resistor can be dynamically adjusted according to the peak torque of the motor under test to change the reversal torque generated by the synchronous generator and realize the dynamic adjustment of the load torque of the motor under test.

[0052] The torque and speed sensor is connected to the motor under test and the synchronous generator on both sides through coupling No. 1 and coupling No. 2, and is used to detect the load torque and speed loaded on the shaft of the motor under test in real time; the torque and speed sensor display is connected to the torque and speed sensor, and is used to display the torque and speed in real time.

[0053] Start the motor under test, and drive the synchronous generator to rotate during the rotation of the motor under test, and the motor under test is subjected to a small load torque. When doing the peak torque impact test, first increase the speed of the motor under test to a certain value according to the value of the peak load torque of the motor under test, so that the synchronous generator can generate a sufficiently large back electromotive force, and then manually adjust the resistance of the variable resistor to a certain value to ensure that the load torque can reach the peak torque of the motor under test; then start the timer, and set the peak torque holding time and load torque holding time of the timer through knobs 1 and 2. The timer will control the opening and closing of the solid-state relay connected to it according to the set time. When the peak torque holding time pulse arrives, the solid-state relay is turned on, the torque loading device circuit is closed, the synchronous generator generates a reverse torque, and the torque value of the motor under test rises rapidly from a small value to the peak torque. The time of the added peak load torque is the solid-state relay opening time. At this time, the torque speed value can be observed through the torque speed display. When the load torque holding time pulse arrives, the torque loading circuit is disconnected, the synchronous generator generates a small load torque, and the motor under test bears this small load torque until the next peak torque pulse arrives. At this point, a working cycle is completed, and the pulse-type change of the load torque of the motor under test is realized.

Claims

1. A high overload pulse type motor torque loading system, characterized in that: It includes a torque loading device, a torque measuring device and a timing device; The torque loading device includes a synchronous generator, a motor to be tested, a variable resistor, a rectifier bridge, a No. 1 coupling, and a No. 2 coupling; the torque measuring device includes a torque speed sensor and a torque speed display; The motor under test is connected to one end of the torque and speed sensor through a No. 2 coupling, and the other end of the torque and speed sensor is connected to the synchronous generator through a No. 1 coupling. The torque and speed sensor is used to detect the load torque value loaded on the shaft of the motor under test and the speed value of the motor under test in real time; the armature winding of the synchronous generator is connected to the AC side of the rectifier bridge, and the DC side of the rectifier bridge is connected in series with a variable resistor and a timing device. The armature winding of the synchronous generator, the rectifier bridge, the variable resistor and the timing device constitute a torque loading circuit; the torque and speed display is connected to the electrical interface of the torque and speed sensor, and is used to display the torque and speed sensor detection value in real time; the motor under test drives the synchronous generator to rotate during rotation, and the load torque borne by the motor under test reaches the peak load torque by adjusting the resistance value of the variable resistor; The timing device includes a timer, a solid-state relay and a DC voltage-stabilized switching power supply; the two input ends of the timer are respectively connected to the positive and negative electrodes of the DC voltage-stabilized switching power supply, and the two output ends of the timer are respectively connected to the positive and negative terminals of the solid-state relay input end; one end of the solid-state relay load end is connected to the DC side of the rectifier bridge, and the other end of the solid-state relay load end is connected to a variable resistor; the timer is used to set the peak torque holding time and the load torque holding time, and the solid-state relay is turned on and off according to the peak torque holding time and the load torque holding time set by the timer, and the opening and closing of the solid-state relay controls the closing and opening of the torque loading circuit; the DC voltage-stabilized switching power supply supplies power to the timer; The timer includes a first display screen, a second display screen, a first knob, a second knob and a control chip; the control chip is used to program the timing logic of the timer; the first knob is used to set the peak torque holding time, and the peak torque holding time is displayed on the first display screen; the second knob is used to set the load torque holding time, and the load torque holding time is displayed on the second display screen; when the timer works within the peak torque holding time, the solid-state relay is turned on, the torque loading circuit is closed, and the motor under test is subjected to the peak load torque; when the timer works within the load torque holding time, the solid-state relay is turned off, the torque loading circuit is disconnected, and the motor under test is subjected to a small load torque; The micro load torque refers to a torque value ≤ 0.1% FS; The voltage value of the DC regulated switching power supply is 15VDC.

2. A loading method using the high overload pulse type motor torque loading system as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Start the motor under test. The motor under test drives the synchronous generator to rotate through the No. 1 coupling and the No. 2 coupling. At this time, the motor under test is subjected to a small load torque. Step 2: According to the maximum value of the peak load torque of the motor under test, the speed of the motor under test is increased to a certain value, so that the synchronous generator generates a back electromotive force that matches the maximum value of the peak load torque of the motor under test; and then the resistance value of the variable resistor is adjusted so that the load torque of the motor under test reaches the peak torque of the motor under test; Step 3: Start the timer, adjust knob No. 1 and knob No. 2 to set the peak torque holding time and load torque holding time of the timer respectively; when the peak torque holding time start pulse arrives, the solid-state relay is turned on, the torque loading circuit is closed, the synchronous generator generates a reverse torque, the torque value of the motor under test rises to the peak load torque, the motor under test bears the peak load torque until the next load torque holding time start pulse arrives, and the time of the peak load torque applied to the motor under test is the set peak torque holding time; when the load torque holding time start pulse arrives, the torque loading circuit is disconnected, the synchronous generator generates a small load torque, the motor under test bears the small load torque until the next peak torque holding time start pulse arrives, and the time of the small load torque applied to the motor under test is the set load torque holding time; the load torque value loaded on the shaft of the motor under test and the speed value of the motor under test are displayed on the torque and speed display; thereby realizing the pulse-type change of the load torque of the motor under test.

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