I have a 415V 3 phase motor, but during emergency situation a 110V DC to 220VAC 3 Phase inverter comes into place. What will be the effects on the motor

  • \$\begingroup\$ What does the motor manufacturer say? \$\endgroup\$ – Andy aka Jan 21 '15 at 11:42
  • \$\begingroup\$ There is nothing mentioned by the manufacturer. The Inverter part came later into the design as a result this problem. \$\endgroup\$ – Karthik Shetty Jan 21 '15 at 11:52
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    \$\begingroup\$ Have you tried asking them? Also, have you considered that the 220Vac invertor actually produces a line-to-line voltage that is 381 volts? \$\endgroup\$ – Andy aka Jan 21 '15 at 12:09
  • \$\begingroup\$ Is your inverter 220 VAC or 240 VAC? Your question is inconsistent. Note that 240 VAC phase-to-neutral in a Y configuration is the same thing as 415 VAC phase-to-phase. \$\endgroup\$ – Dave Tweed Jan 21 '15 at 14:26
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    \$\begingroup\$ Could it be possible one piece of equipment is stating line-line (usual for 3ph equipment) and the other stating phase voltage (typical for aerospace and equipment that can operate single phase). \$\endgroup\$ – JonRB Jan 21 '15 at 16:05

Ignoring changes to efficiency and power factor if the output power stays the same, then the input power must stay the same and the only way for that to happen when the voltage decreases is for the current to increase. If this causes the current to go above the rated current, then your motor will start to overheat and you could see shortened life. In your situation, \$\frac{415}{220}=1.88\$, so the current should increase by about \$1.88\$ times the normal current.

However, a torque is related to the voltage squared, so your starting torque and pull up torque will be decreased to about \$(\frac{220}{415})^2=0.33\$ of the rated values. You may have trouble starting any loads in this situation.

  • \$\begingroup\$ Sorry, but I had to downvote. See Dave Tweed's comment. This is 3-phase power, and it can be specified in different ways. \$\endgroup\$ – WhatRoughBeast Jan 21 '15 at 15:45
  • \$\begingroup\$ @WhatRoughBeast, if Karthik Shetty comes back and clarifies what his voltage is, I will update my answer. Or do you think I should make the answer more general, not including specific voltages? \$\endgroup\$ – Eric Jan 21 '15 at 16:44
  • \$\begingroup\$ Voltage is 220V Line to Line 3 Phase \$\endgroup\$ – Karthik Shetty Jan 22 '15 at 3:39

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