Ammeter range on the motor control column
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The motor is equipped with a local control panel, which is required to have an ammeter. How should the range of this ammeter be determined? Is it determined by adding a certain margin to the motor’s rated current?
This is related to the maximum current at startup and the normal range of current fluctuations.
The ammeter on the control column is matched to the turns ratio of the current transformer, with the range scale typically set so that the rated operating current falls between 1/2 and 2/3 of the gauge scale
In accordance with the petrochemical standards: Article 8.3.10 of \"SH 3038-2000 Technical Specifications for Electrical Design of Units in Petrochemical Enterprises\", current meters should be installed near motors with a power rating of 37 kW or higher, or those for which it is necessary to monitor the current during operation.
Now some large design institutes no longer follow this standard, relying mainly on the requirements during operation
SHT 3038-2017 Code for Electrical Design of Petrochemical Plants – this specification has been revoked
The ammeter is used in conjunction with the CT secondary side; the CT primary current should be selected at 1.25 times the rated current of the motor