Load Wire Inductance - Prodigit 3350F Series Operation Manual

3350F Series Operation Manual 21

2-21. Load wire inductance

The load wiring has an inductance (L). When the current (I) varies in short time period, It
Generates a large voltage at both ends of the wiring cable. This voltage applies to all of the
Load input terminals of the 3350F series when the impedance of the EUT is relatively small.
The voltage generated by the load wire inductance (L) and the current variation (I) is
Expressed using the following equation.
E = L x (∆I /∆T)
E: Voltage generated by the wire inductance
L: Load wire inductance
∆I: Amount of Current variation
∆T: Variation period of current
In general, the wire inductance can be measured approximately 1 µH per 1 meter. If the
10 meters of Load wires is connected between the EUT and the electronic load (3350F
Series) with the current Variation of 2 A/µs, the voltage generated by the wire inductance
Will be 20 V.
The negative polarity of the load input terminal is the reference potential of the external
Control signal, Therefore, the device connected to the external control terminal may get
Malfunctioned.
When operating under the constant voltage (CV) mode or constant resistance (CR) mode or
Constant power (CP), the load current is varied by the voltage at the load input terminal, so
The operation can be affected easily by the generated voltage.
The wiring to the EUT should be twisted and the shortest as possible.
If the load wire is long or has a large loop, the wire inductance is increased. Consequently,
The Current variation that results when switching occurs will cause a large voltage drop.
When the value of instantaneous voltage drops under the minimum operating voltage
Depends on the generated voltage at the load input terminal, the response of recovery will be
extensively delayed.