Understanding Electrical Equipment Ratings

Every piece of electrical equipment carries a nameplate full of ratings. Knowing what they mean lets you confirm a part fits your system before you buy. Here are the ones that matter most.

Voltage (V)

The voltage rating is the maximum system voltage the equipment is designed for — e.g. 240 V, 480 V or 600 V AC for low-voltage gear, and 5 kV, 15 kV or higher for medium-voltage. Equipment must be rated at or above your system voltage.

Amperage (A)

The ampere or continuous-current rating is how much current the device can carry indefinitely. For breakers and fuses it's the trip/interrupt threshold; for busway and switchgear it's the bus rating.

Phase

Single-phase (1φ) is typical for residential and light commercial; three-phase (3φ) powers most industrial equipment and motors. The equipment's phase must match your service.

Frequency (Hz)

60 Hz in North America, 50 Hz in much of the rest of the world. Motors, drives and transformers are frequency-sensitive — confirm it matches.

kVA / kW (transformers & generators)

Apparent power (kVA) and real power (kW) describe capacity. Transformers are rated in kVA; generators typically in kW. Size to your connected load plus headroom.

Interrupting / short-circuit rating (kAIC)

This is the maximum fault current a protective device can safely interrupt, or that switchgear can withstand. It must equal or exceed the available fault current at the point of installation — a safety-critical number you should never downgrade.

BIL (medium voltage)

Basic Impulse Level rates a device's ability to withstand voltage surges (like lightning or switching transients), expressed in kV. It matters when speccing medium-voltage switches and switchgear.

Still not sure a part fits? Send us the nameplate details and we'll confirm compatibility. Browse the catalog or contact our team.