AC Interface Unit

Block Diagram of a Single Phase FineTest AC Interface Unit

Application

Power Supply Testing

Features

AC On/Off Interlock Contactor:

To insure operator safety, this unit prevents the application of input power
until a micro switch in the test fixture's safety cover completes the circuit.



The unit provides 2 output signals for each AC Path:

AC Voltage Monitor:

The first signal is the AC Voltage Monitor, and this signal is the output of a
step-down voltage transformer that is connected between the Phase Voltage
and Neutral. This reduces the 0-500VAC to a 0-5V AC Signal, that can be safely
routed to the scope.

AC Current Monitor:

The second signal is the AC Current Monitor, which is the output of a clamp-on current transformer. By increasing the number of windings, we can achieve a 20:1 Current to Voltage ratio.For example, a 0-100 A current would produce a 0-5 V AC Signal that can be safely routed to the scope.

These signals are used for Inrush Current Tests, Power On Time, Drop Out, Hold Up, and other AC timing tests.



Optional External AC Input:

A mux relay may be added when very high inrush current measurements may exceed the peak current of the AC Source. This relay applies direct Line voltage to the unit under test for the Inrush Current test, and then switches to the AC source for all other tests. This saves the user from upgrading the AC source to a higher power model.

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More Details...

Top view of a Single Phase AC Interface Unit with the cover removed showing:
Clamp-On AC Current Transformers (AC I Monitor)
Step-Down Voltage Transformers (AC V Monitor)
High-Power AC Contactors (AC On/Off & Interlock)

Rear view of a Single Phase AC Interface Unit showing:
AC Input / Output Connectors
Step-Down Voltage Transformers (AC V Monitor) Pot Adjust

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3 Phase AC Interface Unit

Block diagram of FineTest 3 Phase AC Interface Unit
Very similar to the Single Phase AC Interface Unit, except that
now there are 3 Contactors, 3 Current Transformers and 3 Step-Down Transformers

Top view of a 3 Phase AC Interface Unit with the cover removed showing:
3 Clamp-On AC Current Transformers (AC I Monitors)
3 Step-Down Voltage Transformers (AC V Monitors)
3 High-Power AC Contactors (AC On/Off & Interlock)

Block diagram of FineTest 3 Phase AC Interface Unit
Very similar to the 3 Phase AC Interface Unit above, except that
now the 3 Step-Down Transformer AC Voltage Monitors are Phase-To-Phase

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Video Clip of Tests using AC V and AC I Monitors
on the Scope (Duration approx. 1 Min)

To view the video:

Move your mouse over the picture and press play (lower left-hand corner)...

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More Examples using AC V and AC I Monitors

Power-On Time Test on Scope using AC V Monitor signal from AC Interface Unit

Hold-Up Time Test on Scope using AC V Monitor signal from AC Interface Unit

AC Drop-Out Test on Scope using AC V Monitor signal from AC Interface Unit

AC Inrush Current Test on Scope using AC I Monitor signal from AC Interface Unit

20% AC Input Sag Test on Scope using AC V Monitor signal from AC Interface Unit

50% AC Input Sag Test on Scope using AC V Monitor signal from AC Interface Unit

Note that now we are going from 220VAC to 110VAC, and there is a glitch in the
UUT output voltage!