How to Measure Transformer Current Draw

A transformer is an electrical component that converts one alternating current (AC) voltage to another. A step-up transformer converts the input voltage to a higher voltage. A step-down transformer converts the input voltage to a lower voltage. Knowing how to measure the input current draw of a transformer, whether it's a step-up or step-down transformer, can help to troubleshoot the appliance in which the transformer is used. For example, if the current draw is too high, it can cause the circuit breaker to trip.

Things You'll Need

• Current meter
• Current probes
• Extension cord
• Alligator clips
• Wire nuts
• Wire strippers

Instructions

1. Determine the transformer's input voltage. For most household devices and appliances, it will be 120 volts AC. If there is any doubt, check the owner's manual.

2. Create a spliced wire in an extension cord. Use wire strippers to cut into the cord and expose one of the wires. Use a wire nut to connect one of the wires from your cut. Use the current probes and alligator clips to connect the other line.

3. Plug the extension cord into the electrical outlet. Turn the appliance or device on. Make sure the current meter is turned on.

4. Read the numbers on the current meter. For most electrical appliances and devices, the input power cable is directly connected to the transformer, which step the voltage up or down for use by the rest of the electronic circuitry. The numbers on the meter display show how much current the transformer is drawing--in amperes.

Tips & Warnings

• Electricity can cause shocks. Use extreme caution when working with electronic devices.

Resources

• Electrical Safety Manual