Say I have a DPDT relay, like T92S7D12-24. The contacts of this relay are rated for 30A, but there are two sets of contacts. Can I parallel the contacts to get an effective 60A relay? Further, could I parallel two (or more) relays and get even more current capacity?
I see two possible problems.
- Current may not be shared equally between sets of contacts and between relays. One set of contacts could take more than their share of the current and overheat.
- Switching times may vary between contacts and between relays. When breaking with current through the contacts, the last set of contacts to open may be carrying far more than their recommended current at time of break. This could cause damage.
Are these problems? Are there other problems? If so, can they be quantified and worked around? Or is paralleling contacts and relays always bad design practice?
In my specific application, I'm using these relays as part of precharge for a capacitor bank. They are not expected to switch current. They make once the caps are charged, then hold. They should never open under current flow. Under these specific circumstances, should I still expect problems?