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Unidrive Regen Installation Guide
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Issue Number: 2
1.2
Power flow
The phasor diagram in Figure 1-2 illustrates the relationship between the supply voltage and the Regen drive voltage. The angle between the two
voltage vectors is approximately 5° at full load, giving a power factor which is near unity.
The direction of the power flow can be changed relative to the supply voltage, by making small changes to the Regen drive output voltage and phase.
A fast transient response is achieved by means of a space vector modulator.
1.3
Advantages of Unidrive operating in Regen mode
The main advantages for an AC Regen system are:
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Energy saving
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The input current waveform is sinusoidal
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The input current has a near unity power factor
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The output voltage for the motor can be higher than the available AC mains voltage
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The Regen drive will synchronise to any frequency between 30 and 100Hz, provided the supply voltage is between 380V -10% and 480V +10%
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Under conditions of AC mains instability, a Unidrive Regen system can continue to function down to approximately 150Vac supply voltage without
any effect on the DC bus voltage and hence on the operation of the motoring drives (increased current will be taken from the AC supply to
compensate up to the current limit of the Regen drive)
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The Regen and motoring drives are identical
