Now there are four kinds of dynamometers on the market for customers to choose from: HD hysteresis dynamometer, MPD magnetic powder dynamometer, ECD eddy current dynamometer, and electric dynamometer. AIP editor has an article dedicated to introducing dynamometers. The classification and characteristics of the cooling system will not be described in detail in this article. The cooling methods are divided into air-cooled F, water-cooled W, compressed air-cooled A and blower cooling B.

No single dynamometer is compatible with all motors! Each dynamometer has its scope of application and objects, and it needs to be selected according to the actual parameter specifications of the motor. How do we choose a dynamometer?

The selection of a dynamometer should start from the following four aspects.

1. Motor torque

Before choosing a dynamometer, you need to know the maximum torque of the motor. If you don’t know, you can estimate it according to the following formula. Considering that “when selecting an instrument, the measured value should be within the range of 20%~95% of the instrument’s range” (see Chapter 4.2.2 of "Single-phase Asynchronous Motor Test Method GB/T9651-2008", based on the above, we share the maximum torque estimation formula of the motor as follows:

Maximum torque of induction motor: TN=(P2*9.55)/(no*0.9)*2 no: no-load speed

Maximum torque of series motor: TN=(P1*η*9.55)/(no*0.6)*2 no: no-load speed P2: output power (W) P1: input power (W) no: no-load speed η: efficiency

Confirm the maximum torque of the motor, select the corresponding dynamometer model, and ensure the accuracy and safety of the test.

2. Motor speed

Speed and torque are two inseparable parameters of the motor, and they are in an "inversely proportional" relationship. The maximum speed of the motor is also a parameter that must be paid attention to when selecting a dynamometer. If the speed exceeds the limit, the dynamometer will easily cause irreversible damage. Damage, such as fatal problems such as hysteresis dynamometer rotor cracking, magnetic powder dynamometer demagnetization, etc., confirm the maximum speed of the motor and select the corresponding parameter dynamometer to ensure that the no-load speed of the motor is within the safe range of the dynamometer. According to different dynamometers' Machine types, and experience values: choose an eddy current dynamometer above 8000rpm; choose hysteresis dynamometer between 800rpm and 15000rpm; choose magnetic powder dynamometer below 1000rpm. type.

Note: The maximum speed is the speed when the motor is no-load

3. The maximum power of the motor

The maximum power refers to the maximum power point of the motor during operation, because the dynamometer loads the motor from no-load to stall, and the electrical energy in the process is converted into mechanical energy and heat energy, and the temperature of the motor and the dynamometer will continue to rise, so the output power of the motor must be less than the operating power of the dynamometer, otherwise it will cause equipment damage to the dynamometer due to heat superposition. The operating power of the dynamometer is divided into short-term operating power (within 6 minutes) and continuous operating power ( More than two hours), the short-term operating power is greater than the contact operating power, and the length of the loading time depends on the cooling level of the dynamometer, which also determines the cooling method of the dynamometer (described in the first paragraph of this article).

4. Accuracy of dynamometer

Different precision requirements correspond to different grades of equipment. As a high-precision laboratory equipment, the accuracy of the dynamometer is the main measurement index. Now the 0.5 and 0.2 grades in the market are both high-precision. It is recommended that motor companies choose these two precisions, and In November 2012, the implementation of "Three-phase Asynchronous Motor Test Method GB-T1032-2012" stipulated: "When measuring the efficiency of the motor, in order to ensure the accuracy and repeatability of the test results, the accuracy level of the instrument should not be lower than 0.2 "So the three-phase asynchronous motor test should meet the requirements of the national standard. The accuracy of the equipment is the guarantee of the quality of the motor. In order to support the enterprise to use of high-precision equipment, you only need the price of 0.5-level equipment to buy AIP's 0.2-level precision equipment. , to achieve a win-win situation.

The dynamometer can be selected based on the above four aspects. If you do not know the specific model, you can consult a professional to provide you with a corresponding test plan. Choosing the right equipment the guarantee accurate data.

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