When to Choose Between Series and Parallel Output of High Current Tester?

There is a set of "series parallel pressure plates" on the HZ-109S panel, and many engineers who are using this instrument for the first time do not understand the function of this switch - if they choose the wrong one, either the current cannot be output or the required range cannot be reached. Explain this issue clearly, and on-site operations will not get stuck.

Parameters for two output modes

Parallel output: maximum current 1000A, maximum no-load voltage 5V

Series output: maximum current 500A, maximum no-load voltage 10V

How to switch

The series parallel button (pressure plate) on the panel: the center position of the pressure plate=series connection; Press down=parallel connection. This design is opposite to the normal switch logic, and the pressure plate status should be confirmed before operation.

When to choose parallel connection

The manual specifically states that as long as the output current requirements can be met, parallel output should be used as much as possible. This is a clear suggestion from the manufacturer, for the following reasons:

Under parallel connection, two sets of coils in the transformer are connected in parallel, resulting in lower internal resistance, stronger load capacity, smaller voltage drop under the same load conditions, and more stable output current. At the same time, the current stress of each group of coils in parallel is lower, and the operating temperature of the instrument is lower, which is beneficial for the service life of the equipment.

In most experimental situations, parallel output is sufficient for currents within 500A, and parallel is preferred.

When must I choose serial connection

When the impedance of the test sample is high and the parallel output of 5V no-load voltage is insufficient to drive the required current, it is necessary to switch to series mode - the series output no-load voltage reaches 10V, which can drive higher impedance loads to achieve the target current value.

Typical scenario: Some high aspect ratio CTs have multiple turns of the primary coil and high impedance; Alternatively, if a larger secondary current is required and the test wire is longer (with higher wire impedance), parallel 5V drive may not be sufficient. Switching to series 10V can solve the problem.

Switching timing

The series parallel mode can only be switched when the output is stopped, and the pressure plate must not be operated with current output, otherwise it will cause instantaneous high current impact and damage the instrument. Stop the output first (reset the voltage knob to zero, cut off the output), confirm that the current is zero, then switch to series parallel connection and restart the current.