I need to turn ON/OFF a 220Vdc, 500W motor as well as changing it’s speed and reversing direction using PLC and 3 relays as shown in attached drawing. I am planning to supply 160Vdc for high speed and 35Vdc for low speed using step down transformer combined with rectifier. My question lies on the relay. What relay size should I use? Although I can find relay with 10 - 15A rating, most of them are rated in AC-1 (resistive load). According to my understanding, the rating will become much lower when used for DC inductive load especially with higher DC voltage. Furthermore, I can only find DC rating up to 48 VDc at most. I can't find any relay spec for 160VDc. The best component I found so far is ABB's AF contactor series which has DC-13 specification. However, I was very surprised to find that their AF09-30-10-13 series which is rated at 25A AC-1 is only rated 0.27A in DC-13 220Vdc. I was planning to just use large oversized relay (80 to 120A rating @ AC-1) for driving high voltage DC load but I am not sure anymore after reading the ABB's spec.
I am all ears if anyone have any suggestion.
EDIT: Actually, both relay Fast and Relay Run are actually handling AC current as they operate before the rectifier. Therefore, only Relay Fwd is exposed to DC current as it's function is to reverse motor's direction. However, that relay will only trigger before and after motor run. So it behave more like railway track that switch position before the train pass. Having this behavior, do I still need to worry about relay's arc, welding, or any other related issue? Is it safe to just use standard 15A relay rated for AC-1 ?