Reverse Polarity on AC input BLF

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Reverse Polarity on AC input BLF

Postby om_tech_support_JT » Mon Mar 17, 2014 11:35 am

Q: I currently have a single phase, 230VAC powered BLF series brushless DC motor package installed on my machine. This machine will be shipped to Europe. The power adapter they are using does not have polarity indicated on it. Unlike our receptacle which has one slot slightly longer than the other to indicate the polarity, theirs do not have the same polarity indication. What happens if they connect the driver in reverse-polarity?

A: Since AC power source changes the current flow direction at either 50Hz, or 60Hz, it will not affect the motor operation. Your motor will still operate the same way regardless of the power source polarity. However, we recommend connection on the correct polarity due to safety reasons.

The AC power source usually has 3 wires, live, neutral, and earth ground. The master switch is often installed on the live wire side. Therefore, when connected following the correct polarity with switch at OFF position, the neutral wire does not carry any current so if the maintenance personnel accidentally touch the neutral wire, it is relatively safe since there’s no current.

If the motor is connected in reverse polarity, now the master switch will actually be on the neutral side. Therefore, even with the switch OFF, if the maintenance personnel touched the neutral wire on the motor, which is now connected to the live wire of the power source, which will create an electrical shock hazard if the maintenance personnel were not properly insulated from ground. Therefore, using the correct polarity is strongly recommended for safety.

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