Appendix A – DC Power Supply Design
05/2008
Danaher Motion
116
S200-VTS Product Manual
The time domain of motor-related energy flow is measured in milliseconds. The inductive
voltage drop in the bus and ground wiring for these times is small. For this reason, the energy
leveling bus capacitor does not need to be located near the drive and a single bus capacitor
can be shared by multiple drives.
NOTE
Be aware of bus resonance.
Current can oscillate between capacitors in any distributed DC power system with the capacitor
located apart and connected in parallel with wires. The capacitors and wiring inductance form
an underdamped LC circuit that can ring when excited by PWM currents.
The easiest way to monitor the current in the bus wiring of the drive is with a current probe.
The ringing occurs if the current probe shows a large (> 10 A) quasi-sinusoidal current in the 1
to 10 kHz range. While more difficult to see in voltage, it does cause small sinusoidal voltage
(few volts) to occur across the drive positive Bus (J1-3) to Gnd (J1-2) terminals.
Occasional bursts of bus ringing are usually not too serious, but sustained or too frequent
ringing is undesirable because high currents can cause heating of wires and capacitors.
The simplest way to squelch bus ringing is to lower or change the inductance of the bus wiring
with the following:
a. Move the external bus capacitor closer to the drive
or
b. Twist the bus and ground wires between the drive and supply
or
c. Add extra capacitance (470 µf or more) near the drive bus terminals
12. Recommended External Bus Capacitors
Aluminum electrolytic, computer-grade, screw top cans are available with panel mount
hardware. The voltage rating should exceed the maximum bus voltage. Choose a cap with a
100 V rating for operation at 75 V bus nominal. The important capacitor parameter is
capacitance (energy storage), so an 85° C, general-purpose type (such as are listed below) is
acceptable.
Panasonic G-AA series
1.375 x 4.125
8,200 µf 100 V
EEGAA2A822CKE
2 x 4.125
22,000 µf 100 V
EEGAA2A223FKE
3 x 4.125
47,000 µf 100 V
EEGAA2A473HKE
Cornell Dubilier DCMC series
1.375 x 4.125
8,600 µf 100 V
DCMC862U100AC2B
2 x 4.125
20,000 µf 100 V
DCMC203U100BC2B
3 x 4.125
49,000 µf 100 V
DCMC493U100DC2B
United Chemicon U36D series
1.375 x 4.625
8,200 µf 100 V U36D100LG822M35X117HP
2 x 4.625
18,000 µf 100 V
U36D100LG183M51X117HP
3 x 4.625
47,000 µf 100 V
U36D100LG473M76X117HP
A.2
Two Power Supply Operation
Powering the drive control power separately from the bus power has the advantage that fault
and status information is preserved when bus power is down for safety.
Wire the control supply positive terminal to J1-1 (+CTRL) and the control supply negative
terminal to J1-2 (Bus/Ctrl Gnd). Wire the main supply positive terminal to J1-3 and its negative
terminal to J1-2. J1-2 is a shared ground for control power and main power. Separate ground
wires from the two supplies should join at or near the shared drive ground pin (J1-2).
NOTE
The drive can be damaged if the supply voltage exceeds
90 V, even briefly.