求助：关于电动产品安全测试标准的理解（非常急）

蓝色妖姬

本人在玩具实验室负责电动玩具安全测试，实验室目前正在开发新的测试项目，以下是16CFR PART1505标准中的电动玩具过载测试方法，本人对画线部分不太理解，
其中的 “such that any single pole, current-rupturing device will be located in the ungrounded conductor of the supply circuit”
和 “to be positive with respect to a single pole, current-rupturing device”
该如何理解，测试中该如何操作？ 3-ampere plug fuse 该如何接地？
望高手帮忙解释，非常谢谢！

Overload test:
(i) A motor-control switch that is a part of a toy shall be horsepower-rated to cover the load or shall be capable of performing acceptably when subjected to an overload test consisting of 50 cycles of operation by making and breaking the stalled-rotor current of the toy at maximum rated voltage. There shall be no electrical or mechanical failure nor any visible burning or pitting of the switch contacts as a result of this test.
(ii) To determine if a motor-control switch is capable of performing acceptably when subjected to overload conditions, the toy shall be connected to a grounded supply circuit of rated frequency and maximum rated voltage with the rotor of the motor locked into position. During the test, exposed dead metal parts of the toy shall be connected to ground through a 3-ampere plug fuse such that any single pole, current-rupturing device will be located in the ungrounded conductor of the supply circuit. If the toy is intended for use on direct current, or on direct current as well as alternating current, the exposed dead metal parts of the toy shall be so connected as to be positive with respect to a single pole, current-rupturing device. The switch shall be operated at a rate of not more than 10 cycles per minute. The performance of the toy shall be considered unacceptable if the fuse in the grounding connection is blown during the test.