How to expand the range of AC ammeter?

When measuring large AC currents, current transformers are often used to expand the range of electromagnetic AC ammeters. The wiring method is shown in Figure 3-6. When wiring, the primary winding of the current transformer is connected in series with the load in the circuit, and the secondary winding is connected to the AC ammeter. For the convenience of measurement, the rated current of the secondary winding of the current transformer is generally designed to be 5A, and the range of the AC ammeter used with it should also be 5A. The actual current value measured should be the instrument indication value multiplied by the current transformer's conversion ratio. The AC ammeter is generally installed on the distribution board, and the calculated scale numbers are marked on the dial. The measured current value can be directly read from the dial.

When using a current transformer, the secondary winding and the core should be reliably grounded, and no fuse should be installed in the secondary winding. It is strictly forbidden to open the circuit during use.