Design of a new torque standard machine based on a torque generation method using electromagnetic force

Abstract

To allow the application of torque standards in various industries, we have been developing torque standard machines based on a lever deadweight system, i.e. a torque generation method using gravity. However, this method is not suitable for expanding the low end of the torque range, because of the limitations to the sizes of the weights and moment arms. In this study, the working principle of the torque generation method using an electromagnetic force was investigated by referring to watt balance experiments used for the redefinition of the kilogram. Applying this principle to a rotating coordinate system, an electromagnetic force type torque standard machine was designed and prototyped. It was experimentally demonstrated that SI-traceable torque could be generated by converting electrical power to mechanical power. Thus, for the first time, SI-traceable torque was successfully realized using a method other than that based on the force of gravity.

Development of a novel microforce-generating machine based on a force generation method using electromagnetic force

“…There are two measurement modes in a conventional Kibble balance experiment: a dynamic mode for evaluating the eigenvalue associated with the coil and magnet equipped in the Kibble balance, and a static mode for measuring the mass of a standard weight. As in the rotary Kibble balance experiment, we also proposed two measurement modes, dynamic and static, in our novel method, as shown in figure 2 [8,11].…”

“…located at the National Institute of Advanced Industrial Science and Technology (AIST) has developed a 2 N dead-weight type force standard machine [6,7], which can realize a force in the range of 10 mN to 2 N. However, the uncertainty associated with realizing a force of less than 10 mN using small dead-weights becomes excessively large because of limitations due to the manufacturing technology and calibration of small weights. Therefore, a rotary-type microforce-generating method has been proposed [8] by referring to the principle of a Kibble balance [9,10] and the electromagnetic-forcetype torque standard machine developed [11]. Kibble balances have been developed at many NMIs, originally for the precise measurement of Planck's constant, which contributed to the redefinition of the kilogram, and they are now used as an accurate realization method for mass and force standards [12][13][14][15][16][17][18][19][20][21].…”

Dissemination of the Kilogram Following Its Redefinition

“…Using an adapted Kibble balance to generate torque has the potential to improve both the accuracy and reliability of torque generation and measurement. The development of apparatus such as the Electronic NIST Torque Realizer (ENTR) [14] shown in Figure 6 or the new torque standard machine of NMIJ-AIST [15], [16] is already underway. In late 2021 a new key comparison was started, the results of which will contribute to the determination of a new Consensus Value.…”

Uncertainty Evaluation Method of a Dynamic Torque Generating Machine Using Electromagnetic Force

“…There is a relationship between the torque 𝑇 generated when current 𝐼 is applied to a rectangular coil in a uniform magnetic field 𝐵 (case 1) and the induced electromotive force 𝑉 generated when the rectangular coil is rotated at a constant angular velocity 𝜔 in a uniform magnetic field 𝐵 (case 2), as shown in equation ( 1), [4] 𝑇 𝜔 = 𝑉 𝐼 .…”