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在三相三线制交流电路中，常用一个交流电表，两个电流互感器和一个电流换相开关（转换开关）测量三相电流，它可监视三相电流是否平衡，特别是对大容量电动机，可用一块电流表监控三相电流。其电路如下图所示：

In three-phase three-wire AC circuit, one AC meter, two current transformers and one current commutation switch are often used to measure three-phase current. It can monitor whether the three-phase current is balanced or not, especially for large-capacity motors, one current meter can be used to monitor three-phase current. Its circuit is shown in the following figure:

1个电流表和2个互感器测量三相电流

Measuring Three-phase Current with One Amperometer and Two Transformers

1个电流表和2个互感器测量三相电流

Measuring Three-phase Current with One Amperometer and Two Transformers

当旋转式电流转换开关旋转到M1与A，M2与B、C相接时，测量A相电流；当M1与C，M2与A、B相接时测量C相电流；当M1与B，M2与A、C相接时，测量B相电流，这样可以节省两只电流表。

When the rotary current conversion switch rotates to M1 and A, M2 and B, C phase current is measured; when M1 and C, M2 and A, B phase current is measured; when M1 and B, M2 and A, C phase current is measured; when M1 and B, M2 and A, C phase current is measured, so two ammeters can be saved.

在使用旋转式电流换相开关时，要注意以下几点：

When using rotary current commutation switch, the following points should be paid attention to:

旋转式电流换相开关在安装接线时，互感器一端必须可靠接地，以防止产生高压；

When installing wiring of rotary current commutation switch, one end of transformer must be grounded reliably to prevent high voltage.

用这种旋转开关只用两个电流互感器就可以测量三相电流；

The three-phase current can be measured by using only two current transformers.

接旋转式电流换相开关时，不许接线可靠，在接线前应检查旋转开关内部触点接触是否良好。

When connecting the rotary current commutation switch, it is not allowed to connect reliably. Before wiring, it is necessary to check whether the contacts inside the rotary switch are in good contact.