ASK plug-in current transformer for indirect measurement of sinusoidal alternating currents. ASK31.3 CURRENT TRANSFORMER, 75/5A, 1.5VA, CL.1. Primary nominal currents from 75 A to 1500 A Secondary nominal current from 1 A or 5 A. Class accuracy: 1. The ASK plug-in current transformers transform high alternating currents - up to 1500 A (primary current) - into small, harmless, measurable currents (secondary current). Secondary currents are standardized and are either 1 or 5 A. At the same time, they galvanically isolate the primary circuit and the secondary circuit from each other. The plug-in current transformer is plugged onto the primary conductor. This saves time-consuming wiring work. The secondary side (usually a measuring device, a display or a control system) is connected with terminals. Plug-in current transformers are available from 75 A with different hole sizes for busbars or cables.