Hammond CT75A 75:5 Toroidal Current Transformer, 2% Accuracy

The CT75A is a 75:5 toroidal current transformer with 2% rated accuracy at a 2 VA burden. It lets electricians and panel builders read up to 75 A of primary current on a standard AC ammeter with a 5 A movement.

Like every model in the series, it uses a toroidal core, a two hole mounting bracket and 24" insulated secondary leads finished with crimped ring connectors. The primary conductor can be bare (uninsulated) in circuits up to 600 V (4 KV Hi pot), or insulated for higher voltages. UL E227616 volume #1, file number X0DW2 applies to the series.

Overall dimensions for the CT75A are A 3.75 in (95 mm), B 1.35 in (34 mm), C 3.25 in (83 mm), D 3.00 in (76 mm), E 0.87 in (22 mm) and F 2.87 in (73 mm), with mounting slots G 0.22 in (6 mm) by H 0.37 in (9 mm). The listed shipping weight is 1.32 lbs (0.60 kg); the series table gives 1.5 lb. It is RoHS and REACH compliant.

To measure current, pass the wire carrying the current through the CT window so it acts as the primary winding, then connect the secondary to an ammeter with a 5 A movement. The series application data uses this ratio as an example: to obtain a 25:5 ratio, a CT75 with 3 primary turns through the window yields 2% accuracy, compared with 3.2% from a CT50 using 2 turns.