# What explains the discrepancy in contact rating vs. max switching power in this relay?

In this data sheet for a CUI Devices PR23-5V-900-1A "1 Form A" mechanical relay, it specifies:

Max switching voltage: 250VAC
Max switching current: 30A
Max switching power: 7500VA


...but also:

contact rating: 1 Form A: 30 A @ 125 Vac


...which seems to imply that it can't actually handle switching the higher voltage/current. It seems like this relay really can switch 30A at 250V (see e.g. the "Life Curve" in the spec sheet), so what confusion explains this apparently contradictory contact rating spec?

• Actually the relay can't switch 30A and 250VAC, it can only switch 30A or 250VAC, but not simultaneously. There are 560W and 7500VA limits too. Also, it is a different thing to switch a 30A load on/off with a relay, than to just pass it through contacts without switching. Commented May 29, 2023 at 20:06
• the voltage rating says that 250 Vac can be switched off without arcing ... higher voltage may cause an electrical arc to develop between the contacts ... that voltage can be affected by the amount of current passing through the contacts because excessive heating in the contact area lowers the breakdown voltage of air Commented May 29, 2023 at 20:24
• @Justme - Thanks; given the rest of the spec sheet, it seems like it is intended for 250VAC/30A switching? See the "Life Curve" graph for example. Re: the 7500VA/560W, my research seemed to indicate that the implication there was AC (7500VA, which is the 250VAC*30A) vs DC rating (560W) -- other relays spec it that way using those units, and anyway why would the relay care about the distinction between true and apparent power? My impression was that they were just sloppy in the spec sheet, but if I'm wrong I'd appreciate being corrected. Commented May 30, 2023 at 19:54
• The relay contacts, when connected, may not care if the AC load is reactive. The relay contacts do care when switching. Capacitive load takes an inrush current spike when contacts are closed, and inductive loads try to keep the current running when opening the contacts so there may be high voltage spikes or arcing. Commented May 30, 2023 at 20:02