© ElectroCraft 2018
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CPP-A12V80A-SA-USB Technical Reference
12.4 Minimum external bulk capacitance
A bulk capacitor is used to delay the bus voltage rising up to the brake resistor On voltage during braking.
This increases the braking resistor Off time, in turn giving more time for the brake resistor to cool. The
capacitor must be rated to a voltage equal or higher than the brake resistor On voltage (set in the
configuration software).
ElectroCraft recommends connecting a capacitor
of 100 μF per each ampere
deceleration current across
J1 pin 1 and pin 2 as shown in section 12.5. For example, the application given in section 12.3.2 has a
deceleration current of 12 A, so it
will need a 1200 μF
capacitor. This recommendation has proven
sufficient in the majority of applications. If further support is needed or this recommendation does not
provide the required performance please contact ElectroCraft.
WARNING!
Installing capacitance value lesser than 100
μF per each ampere deceleration current could result in an
overvoltage fault condition and may result in damage to the drive.
12.5 Connecting External Brake Resistor and Bulk Capacitor
The braking resistor and bulk capacitor wiring is shown in Figure 29.
Temperature Sensitive Device Connection:
The user supplied temperature sensitive device is connected
in series with the brake resistor as shown in Figure 29. Generally the temperature sensitive device should
be mounted in contact with the surface of the brake resistor or very close to it for an effective operation.
Optional Diode connection:
Adding a diode between the positive terminal of the power supply and J1 pin
2 of the drive as shown in Figure 29 will protect the power supply from any back fed overvoltage while
braking. The diode is sized by the application’s maximum reverse voltage and forward current.
Drive
J2
J1
+DC Power
-DC Power
DC Power
Supply
+
Bulk
Capacitor
Diode
Brake
Resistor
Temperature
Sensitive Device
Figure 29: External brake resistor and bulk capacitor connection to the drive
The ElectroCraft Braking Module is designed for this purpose and is compatible with CPP-A12V80A-SA-
USB. Refer section 12.6 for application information.