I was recently asked a question about a dc power supply, aka a voltage source, that would be used to charge a battery module during test: “What is the rise time of this voltage source when applying 0- to 350-V step under a load of 400 mA?” While this question was about charging a battery module, the question is really a general question about how to measure the performance of a voltage source.
The rise-time specification of the questionable power source was specifically stated as a transition from 0 to 600 V at full load current of 2.6 A, and it would take 250 ms. Though this specification was clear, the conditions under which this specification is stated were quite different from the requested conditions. The 0- to 350-V transition was about 60% of the 0- to 600-V specification and the current of 400 mA is about 15% of the 2.6-A specification. Under these less stringent conditions, the rise time is likely less than 250 ms, but how much less?