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Chapter 3 Installation
3.1 Power supply (rating) considerations
WARNING
:Use the following scheme and equation shown below to calculate the power supply rating.
The drive doesn’t need auxiliary voltage ,all of the voltages requested come from an internal flyback
DC-DC converter.
Transformer
The drive has the internal zero signal connected
with the negative (power), consequently:
--
Do Not use auto transformers
--If the transformer is connected using Center-Star,
Do not connect to Ground
--
Do Not connect any points of Transformer Primary or Secondary to Ground
Therefore, use the MiniAx power supply for these.
- Keep the +AT and -AT between the power supply and the MiniAx as short as possible. If shielded cable is
not used twist the 2 cables together.
Voltage: The primary voltage depends on the available main voltage. The secondary voltage will be
calculated according to the motor’s characteristics and according to the voltage drive range.
The Value will be:
V2 (Dc) = VM / 0,8
Where: VM = E+ (Ri x Im)
E = Ke x n° / 1000
VM=Motor voltage(V)
E =motor BEMF(V)
Im = I motor(A)
Ri =Winding resistance(Ohm)
Ke =Voltage constant (V/kRPM)
n° = Max. speed(RPM)
Considering you must keep a certain margin during the motor's breaking phase, you should never exceed a
voltage of 60Vdc (44 Vac from transformer).
The max. value is 80Vdc and the min. value is 20Vdc.
Example:Brushless DC Motor with the following data:
Im =3,8 (A)
Ri = 2,5 (Ohm)
Ke =12 (V/kRPM)
n° = 3000(RPM)
E = 12 x 3000 / 1000 = 36 (V)
VM = 36 + ( 2,5 x 3,8 ) = 45 (V)
V2 = 45 / 0,8 = 56 (V) V1= 56 / 1,41 = 39,8 (Vac)
You'll use a transformer with the secondary V1= 39 Vac OK 44Vac.
AC
Power
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