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G120C display speed

1/29/2016 10:12 AM	Rate (0)
ahi_77 Experienced Member Joined: 10/23/2015 Last visit: 8/15/2025 Posts: 168 Rating: (2)	Hello everyone, I am commissioning an inverter G120C with TIA Portal, mode U/F. I have a speed feedback, even if i don't connect a motor on the Inverter. Is it normal ? Is it possible to know, if a motor connected on the inverter and how ? Thank you

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1/29/2016 10:20 AM	Rate (0)
Jeff Casagrande Posts: 1529 Rating: (203)	Yes, this is normal. U/F control is open loop where the drive is acting as a variable voltage, variable frequency power supply and assumes that the motor is doing what the drive is telling it to do. I suppose you could look at current feedback to determine if a motor is connected. In operation, the current should be greater than 0.
Jeff Casagrande Posts: 1529 Rating: (203)
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This contribution was helpful to 1 thankful Users ahi_77

1/29/2016 11:05 AM	Rate (0)
ahi_77 Experienced Member Joined: 10/23/2015 Last visit: 8/15/2025 Posts: 168 Rating: (2)	Thank you jeff, so we are never sure that the real speed of the motor is the feedback speed from the Inverter. Thank

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1/29/2016 11:15 AM	Rate (0)
Jeff Casagrande Posts: 1529 Rating: (203)	"Real Speed" is a calculated number. It is simply the inverter output frequency with some compensation for slip correction. Fortunately, induction motor speed is proportional to frequency. The only way to measure real speed is with an encoder.
Jeff Casagrande Posts: 1529 Rating: (203)
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