Control Transformer Fuse Sizing Chart

Ip 20 when finger safe terminal andor fuse cover options are installed meets or exceeds ul 5085 nema st 1 and. Transformers over 600 volts the basic rule for transformers rated over 600 volts requires them to have primary and secondary protection.

Bussmann Selecting Protective Devices Handbook 3002

Note that in all of the below transformer protection tables the percentages indicated represent the maximum fuse rating recommended.

Control transformer fuse sizing chart. 125 of the transformer fla. Transformers are primarily used to move high voltage to lower voltage for the purposes of power distribution. While transformers come in a variety of sizes for.

Circuit breaker size or fuse rating up to 250 of transformer rated current for transformers with secondary voltage 1000v or less. Selecting and sizing an industrial control transformer. Secondary sides of transformers and control transformers.

Transformers are devices that transfer voltage between circuits from one level to another through electrical induction. If you need assistance with circuit protection devices such as fuses or breakers or wire sizing please consult a licensed electrical contractor or electrician in your area who will be familiar with state and local codes. The overcurrent protection required for transformers is consider for protection of transformer only.

Overcurrent protection is often required for industrial control transformers resolution. These dual element fuses have sufficient time delay to withstand the high magnetizing inrush currents of transformers. Such overcurrent protection will not necessarily protect the primary or secondary conductors or equipment connected on the secondary side of the transformer.

With a 480v primary 05a fuses are recommended with a maximum rating of 052a permitted using the 250 rule of nec4503. There is a wide amp rating selection in the 0 to 15a range for these dual element fuses to provide protection for even small control transformers. For transformers with primary voltage 1000v or less and current of 9a or more with primary protection not more than 125 of transformer rated current the next size up rule can be applied table 4503b.

How to calculate fuse size for transformers by tim walsh. Calculation size of circuit breaker and fuse are as per nec 4503 as well as size of transformer and transformer full load losses. Industrial control transformer selection inrush va chart series 50 selection inrush va chart series hc va volt amperes 1000.

Three Steps To Select The Right Fuse For Control Circuit Protection