FIGURE 2.8
AZ20 Power Supply Selection
AZ Drive Over Voltage Shutdown (88V)
0
20
40
60
80
100
VDC
Acceptable Power Supply
Range (26 V-72V)
Shunt Regulator Turn-On Voltage (80V)
AZ Drive Under Voltage Shutdown (9V)
System Power Supply Requirement (24V)
MNALAZIN-02
16
Products and System Requirements / System Requirements
Power Supply Specifications
AZ servo drives operate off an isolated unregulated DC Power Supply. The AZ12 and AZ6 drives
have a DC supply range of 20‐80 VDC, while the AZ20 series has a range of 10‐80 VDC. All AZ
servo drives have an over‐voltage shutdown of 88 VDC. To avoid nuisance over‐ or under‐
voltage errors caused by fluctuations in the power supply, the system power supply voltage
should be at least 10% above the entire system voltage requirement, and at least 10% below
the lowest value of the following:
•
Drive over voltage
•
External shunt regulator turn‐on voltage
Use of a shunt regulator is necessary in systems where motor deceleration or a downward
motion of the motor load will cause the system’s mechanical energy to be regenerated via the
drive back onto the power supply. This regenerated energy can charge the power supply
capacitors to levels above that of the AZ drive over‐voltage shutdown level. If the power supply
capacitance is unable to handle this excess energy, or if it is impractical to supply enough
capacitance, then an external shunt regulator must be used to dissipate the regenerated
energy. The shunt regulator will "turn‐on" at a certain voltage level (set below the drive over‐
voltage shutdown level) and discharge the regenerated electric energy in the form of heat.
The diagram below provides a possible example of an appropriate system power supply
voltage for an AZ20 drive using an external shunt regulator.
The power supply current rating is based on the maximum current that will be required by
the system. If the power supply powers more than one drive, then the current requirements
for each drive should be added together. Due to the nature of servo drives, the current into the
drive does not always equal the current out of the drive. However, the
power
in is equal to the
power
out. Use the following equation to calculate the
power
supply
output
current
,
I
PS
,
based on the motor current requirements.
Where:
V
PS
‐nominal power supply voltage
I
M
‐motor current
V
M
‐motor voltage
I
PS
V
M
I
M
⋅
V
PS
0.98
(
)
⋅
-----------------------------
=
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