Input Inrush Current: What Buyers Should Ask Before Group Startup

Describe what switches on together

A single power supply sample working on a bench does not settle every question about an installation that starts several units together. Before requesting a quote, tell the supplier how many supplies share the switching arrangement and whether they start simultaneously or in a defined sequence.

For example, a cabinet with several lighting power supplies may be switched as one group. This is an illustrative purchasing scenario, not a Voltivo installation claim. The RFQ should identify the proposed group and the responsible system engineer, rather than asking only for the wattage of each unit.

Keep AC input inrush separate from output load startup

XP Power explains input protection and inrush limiting, including why a thermistor-based design may specify inrush under cold-start conditions. Its temperature and the time since switch-off matter when reviewing such a specification. A cold-start figure should therefore not silently stand in for every restart condition.

This is an AC input question. The current needed to start a motor or charge capacitance on the DC output belongs in a separate load requirement. Use the capacitive-load startup checklist for that output-side discussion and retain both requirements when both apply.

Request conditions and a waveform, not only a peak number

Ask whether the quoted input inrush value is typical or maximum and request the associated input voltage, temperature, startup state and measurement conditions. Where the system reviewer needs it, request a current waveform or time-duration information for the proposed model. Mark unavailable evidence explicitly.

COSEL notes that breaker trip characteristics matter when evaluating power supply inrush. Procurement should pass the supply evidence and the exact protective-device information to the qualified system designer. This guide does not prescribe a breaker rating or authorize replacing protection to prevent tripping.

A supplier statement that a model has inrush limiting is useful context, but it does not by itself approve a particular multi-unit installation. Ask which stated startup conditions the evidence covers.

Put the installation questions on one sheet

Supply identities

Proposed model, revision and quantity of each model in the group, including mixed-model installations.

AC conditions

Required input range and frequency, with the system engineer identifying the conditions to evaluate.

Switching pattern

Simultaneous or sequential startup, intended sequence and expected off-to-on intervals. Include quick restarts if they are part of normal operation.

Installation information

Switching device, protective-device identity and distribution arrangement, supplied or reviewed by the responsible engineer.

Supplier evidence

Peak and duration information where available, test conditions, document revision and any unconfirmed cases.

Return the same sheet with every quotation. If the installation is not yet defined, distinguish a product proposal from a completed system compatibility review.

Approve the group under an agreed test plan

Ask a qualified engineer or test provider to define the safe evaluation and acceptance criteria. The record should identify the actual group, switching and protection components, input conditions, load states and restart sequence. Keep the results linked to those exact configurations.

Do not infer approval of a larger group from a successful test of one unit. When the number of supplies, switching sequence or model changes, return the affected installation for review. Retain the accepted evidence with the purchasing specification so a later substitution does not lose the original assumptions.

For a Voltivo Power inquiry, provide output requirements, intended number of supplies, simultaneous-start or sequencing needs, restart pattern, destination markets and estimated order quantity. Request the available input inrush documentation for the proposed configuration. Values and suitability must be confirmed for the exact offer; no universal startup limit is implied for the catalog.