Square Wave Feedthrough Capacitor Test Setup

Purpose of the test

This test is performed to make sure that a capacitor can withstand an ephemeral high voltage and can tolerate rapid charging and discharging.

Capabilities of the generator

With this square wave pulse generator one can afford:

1. Accurate pulse width of 2000±10 millisecond
2. A high voltage pulse of amplitude0.0-3.25KV
3. Charging and discharging current of up to 50 Amperes

How the generator works?

First goal is achieved with a low inductance high voltage relay with a response time less than 10 milliseconds.The relay is driven by a square wave generator with output 24 Volts and pulse duration 2000±1 milliseconds.Second requirement is fulfilled by a DC power supply which charges a capacitor bank up to the required voltage level very slowly(Charging current less than 5 milli-amperes).

The third requirement of 50 ampere charging currnet is accomplished through" normally open" terminal of the relay with a constant nichrome wire resistance of 65Ω only.Obviously,the 50 ampere charging current is obtained when the capacitor is used at peak level of  3.25 KV.

When the pulse applied to the relay subsides (Just after 2000 millisecond),the relay turns off and the charging terminal of the capacitoris connected to the normally closed terminal of the relay which in turn is earthed via the same resistor. Hence every load capacitor charges and discharges through the same resistor.

In this particular case the capacitor bank was charged to 1000 volts only.Hence the chargingcurrent of the capacitor under test was less than 16(sixteen)amperes.

ESL and ESR were not measured due to short circuit discharging requirements of the test which could have damaged the capacitor under test instantaneously.