Incorrect phase sequence

An incorrect phase sequence means the inverter's three-phase AC output is wired in A-C-B (negative or counter-clockwise) rotation instead of the A-B-C positive rotation the inverter needs. The inverter will not run in this state and reports a fault, for example Reverse Phase on SGI-XTM units or error 1301 for a left-hand rotating field on SMA Sunny Central CP-XT units. On Yaskawa units the Modbus phase sequence register shows the rotation directly: 1 means CW (ABC), 2 means CCW (ACB) and 0 means not locked. A phase lock loop error, or frequency and voltage readings that look wrong, can also point to reversed rotation. Check the rotation before you suspect a sensor fault. Crossed phases also show up as negative-sequence current. A Reverse Phase message is different from an Open Phase message, which means one phase is missing at the inverter. First check the phase position at the inverter AC terminals and make sure all fuses are switched on. To fix it, have an electrician swap any two AC phase conductors at the inverter output terminals, then restart the inverter. Where a site meter is used, its phase order should match the order at the inverter grid port.

<!-- review notes

• sentence 4: support check: partial - PLL error or odd readings pointing to rotation is stated, but the advice to check before suspecting a sensor fault is not in the passage.
• sentence 6: support check: partial - Check phase position and fuses switched on are stated in u9, but 'at the inverter AC terminals' and 'first' ordering are not stated.
• sentence 4: review: partial - The passage links a PLL error or odd frequency/voltage readings to phase rotation, but never says to check rotation before suspecting a sensor fault. -->