From CNC Teknix Tek10 User Manual
D2.1 Transformer Voltage Rating
The transformer should have a secondary output voltage 0.717 times lower than the DC voltage required
for the motors, ie. If your motors require 65VDC your transformer secondary voltage should be no more
than 65 * 0.717 or 46.6VAC.
D2.2 Transformer Current Rating
The current rating should be large enough to handle all motors running at full power simultaneously. If you
have a 3 axis system with each motor drawing a maximum average current of 10A, then the transformer
secondary should be capable of delivering at least 30A. Note that the servo driver has an adjustable peak
current limit. Average continuous current will be 20 to 60% below this value depending on your motor,
torque and acceleration setup. Conversion of AC to DC does lower this current, as it also raises the
voltage, but with a large filter capacitor it should still be sufficient. If in doubt it is better to get bigger rather
than smaller.
D2.3 Rectifier
Rectification can, in most cases, be a standard bridge rectifier, so long as the current rating is not
exceeded. If the total current draw is in excess of 25A then it is much better to make up a rectifier using
large stud diodes. If you do not have any experience in electronics then it is advisable to seek help in
making up this rectifier.
D2.4 Capacitance
The power supply needs enough capacitance to control the ripple voltage to under 2% at maximum load. A
capacitance (C1) value of this should be such that it provides at least 1,000uF (2,000uF recommended) of
capacity for every 1 Amp of current draw, so if your motors draw a total of 25A then you will need a
capacitance of at least 25,000uF. This can be one large capacitor or 2 or more smaller capacitors
connected in parallel. Mount the capacitance, power supply, as close to the drivers as possible.
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