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  • No : 21450
  • Release Date : 2018/08/22 16:27
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Relationship between frequency and load current

Can can use the inverter to control the motor load current to keep it constant?
(Example) Sample and input the motor load current value to the programmable controller, perform calculation so that the current value is maintained within a certain range, and then control the inverter frequency with 4 to 20 mA output.

When the load increases, the load current value also increases. Does lowering the frequency also lowers the current value proportionally?
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Answer

If the load is heavy and the output current is higher than the control value, you can adjust Pr.22 (Stall prevention operation level) to trigger the stall prevention function at the control value and the output current can be maintained almost constant. However, you cannot obtain sufficient torque. If the output current is lower than the control value, since the inverter cannot forcibly increase the output current, it is not possible to maintain the load current constant at the control value.
Relationship between the output current and output frequency can be expressed as follows:

T = K × (V/f) × I
T: Torque, K: Constant, V: Output voltage, f: Output frequency, i: Output current
Since the inverter keeps the ratio of V/f constant, lowering the output frequency does not reduce the output current proportionally.
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Inverter, magnet motor drive
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