OCPD Location = 1

Primary Voltage = 0

Secondary Voltage = 0

VA =

kVA =

Primary Protective Device = 1

Secondary Protective Device = 1

Primary OCPD =

Secondary OCPD =

m_pi =

m_si =

t_2a = [[2.99;1]; [5.99;3]; [9.99;6]; [14.99;10]; [19.99;15]; [24.99;20]; [29.99;25]; [34.99;30]; [39.99;35];[44.99;40]; [49.99;45]; [59.99;50]; [69.99;60]; [79.99;70]; [89.99;80]; [99.99;90]; [109.99;100];[124.99;110]; [149.99;125]; [174.99;150]; [199.99;175]; [224.99;200]; [249.99;225]; [299.99;250];[349.99;300]; [399.99;350]; [449.99;400]; [499.99;450]; [599.99;500]; [600.99;600]; [699.99;601];[799.99;700]; [999.99;800]; [1199.99;1000]; [1599.99;1200]; [1999.99;1600]; [2499.99;2000]; [2999.99;2500]; [3999.99;3000]; [4999.99;4000]; [5999.99;5000]]

t_2b = [[19.99;15]; [24.99;20]; [29.99;25]; [34.99;30]; [39.99;35]; [44.99;40]; [49.99;45]; [59.99;50];[69.99;60]; [79.99;70]; [89.99;80]; [99.99;90]; [109.99;100]; [124.99;110]; [149.99;125];[174.99;150]; [199.99;175]; [224.99;200]; [249.99;225]; [299.99;250]; [349.99;300]; [399.99;350];[449.99;400]; [499.99;450]; [599.99;500]; [699.99;600]; [799.99;700]; [999.99;800]; [1199.99;1000];[1599.99;1200]; [1999.99;1600]; [2499.99;2000]; [2999.99;2500]; [3999.99;3000]; [4999.99;4000];[5999.99;5000]]

t_3a = [1;3;6;10;15;20;25;30;35;40;45;50;60;70;80;90;100;110;125;150;175;200;225;250;300;350;400;450;500;600;601;700;800;1000;1200;1600;2000;2500;3000;4000;5000;6000]

t_3b = [15;20;25;30;35;40;45;50;60;70;80;90;100;110;125;150;175;200;225;250;300;350;400;450;500;600;700;800;1000;1200;1600;2000;2500;3000;4000;5000;6000]

Calculates the maximum allowed overcurrent protection for the primary and secondary of transformers, based on the requirements of Table 450.3(B) of the 2014 National Electrical Code.

Input the transformer ratings and select whether primary only or primary and secondary overcurrent protection will be provided and the calculator will determine the maximum rating of the overcurrent protective device. NOTE: Secondary overcurrent protection is required for most transformers. Refer to section 240.21(C)(1) of the 2014 National Electrical Code to verify that the installation complies with code requirements if primary overcurrent protection only is chosen.

- Location: Primary Only or Primary and Secondary.

- Primary Voltage rating at the primary of the transformer.

- Secondary Voltage rating at the secondary of the transformer.

- VA: Transformer rating in volt-amps(VA). If volt-amps is entered, leave kVA as 0 (do not use next field).

- kVA: Transformer rating in kilovolt-amps(kVA). If kilovolt-amps is entered, leave VA as 0 (do not use previous field).

- Primary Protective Device: Fuse or Circuit Breaker based on the protective device to be used for the primary overcurrent protection.

- Secondary Protective Device: Fuse or Circuit Breaker based on the protective device to be used for the secondary overcurrent protection.

- Primary OCPD: Maximum allowed rating of the overcurrent protective device on the primary side of the transformer.

- Secondary OCPD: Maximum allowed rating of the overcurrent protective device on the secondary side of the transformer.

Calculate the maximum overcurrent protection allowed on the primary and secondary of a 75 kVA, 3 phase, 480:208/120 volt transformer if circuit breakers will be used as the overcurrent protective devices?

- Location: Primary and Secondary

- Primary Voltage Rating: 3∅, 480 volts

- Secondary Voltage Rating: 3∅, 208 volts

Transformer Rating

- VA: 0

- kVA: 75

- Primary Protective Device: Fuse

- Secondary Protective Device: Fuse

The Primary Overcurrent Protection Device needed is 225 amps while the Secondary Overcurrent Protection Device needed is 300 amps.

OCPD Location

Primary Voltage

Secondary Voltage

VA

kVA

Primary Protective Device

Secondary Protective Device

Primary OCPD

Secondary OCPD

-------------