Relay rating

[AxleD]

Hi All,

Just need some clarity on the DC current switching capability of a relay. The relay part # is HF115F and i have included some of the specs from the datasheet (not sure if i could post the whole datasheet).

1. There is no reference to DC current handling capability. Can this relay safely handle 1.5A DC at 30V?
2. What does the contact resistance (1A 6VDC) refer to?

Thanks for the assistance.

[Zero999]

1) Of course, if it can switch 8A at 300VDC then 1.5A at 30VDC will be no problem.
2) That's just the test conditions for measuring the contact resistance which is no more than 100mA @ 1A & 6V.

[Psi]

It really depends what DC load you are switching.

If the load is purely resistive and steady (no inrush current) then you can switch 8A no problem.

If there's lots of inrush current derating as low as 20% is sometimes needed to get good lifespan. Typical inrush current from say a lamp can be 10 times higher than the steady current.

If the load is highly inductive then you will get a lot of arcing when the relay breaks contact and this will slowly damage the contact surface.  50% is a good rule of thumb.

If switching a motor a 40% derating is advisable.

Since your relay is 8A rated and you only need 1.5A you are covered for all options.

[AxleD]

Thank you both!

[bktemp]

1) Of course, if it can switch 8A at 300VDC then 1.5A at 30VDC will be no problem.

It can switch 300V DC or it can switch 8A, but not 8A at 300V.

On the last page of the datasheet there is a nice curve showing the maximum switching power depending on voltage and current for both AC and DC conditions.
30V 1.5V is possible, but close to the limit. If you have an inductive load I would not use this relais.

[Zero999]

1) Of course, if it can switch 8A at 300VDC then 1.5A at 30VDC will be no problem.

It can switch 300V DC or it can switch 8A, but not 8A at 300V.

On the last page of the datasheet there is a nice curve showing the maximum switching power depending on voltage and current for both AC and DC conditions.
30V 1.5V is possible, but close to the limit. If you have an inductive load I would not use this relais.

That makes sense but it would've been nice if the full datasheet was posted, rather than a tiny extract from it.