Every manufacturer recommends against running a drive on an ungrounded system. If it's ungrounded you will need to disconnect a jumper somewhere on the drive. Grounding is a mechanism to protect distribution equipment and people under normal operating conditions, abnormal operational (overcurrent and overvoltage) responses, and hazardous conditions such as shocks. Grounding is necessary to assure correct operation of electrical devices, to assure safety. In industrial power systems with ungrounded or high-resistance grounded neutrals, most unplanned outages trace back to a single root cause: a ground fault that was either undetected, mishandled, or allowed to persist until a second fault brought the system down. Even though the system is not connected to the ground, there exists a connection to the ground due to the presence of capacitances between the live conductors and the ground.
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