NEMA contact ratings
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NEMA contact ratings are how much current at a rated voltage a relay or other pilot device can switch. The current rating of smaller NEMA contactors or their auxiliaries are defined by NEMA ICS 5: Industrial Control and Systems, Control Circuit and Pilot Devices[1] standard. The nomenclature is a letter followed by a three-digit number, the letter designates the current rating of the contacts and the current type (i.e., AC or DC) and the number designates the maximum voltage design values.
| Contact Rating Designation | Thermal Current | Voltage |
|---|---|---|
| A150 | 10 | 150 |
| A300 | 10 | 300 |
| A600 | 10 | 600 |
| B150 | 5 | 150 |
| B300 | 5 | 300 |
| B600 | 5 | 600 |
| C150 | 2.5 | 150 |
| C300 | 2.5 | 300 |
| C600 | 2.5 | 600 |
| D150 | 1 | 150 |
| D300 | 1 | 300 |
| E150 | 0.5 | 150 |