Curtiss-Wright | Tritex II AC 90, 115 Rev. X PN39892 7/12/22
Do not continue normal operation after reaching
temperature or current limits.
If the fault action is other than DISABLE, the user must
disable the drive as soon as possible if any of these conditions occur.
Failure to act on these conditions can cause permanent damage to the
drive or motor/actuator. Such damage will not be covered under
warranty.
Brake / Shunt Resistor Considerations
Many applications require a brake (or “braking” or “shunt”) resistor to
dissipate energy regenerated from decelerating an inertial load, lowering
a vertical load, or relaxing a return spring. There is little energy storage in
internal capacitors and Tritex II AC does not return energy to the AC line.
With gear motors and linear actuators, inertial energy is often not a
significant factor. Vertical loads and return springs must always be
considered a source of regenerated energy. A high bus fault will occur if
an application requires a braking resistor but does not have one
installed.
Terminals R1 and R2 on the power terminal block are provided for
connection of an external Brake / Shunt resistor only. Each drive must
have an independent resistor connected to only one drive. No other
connections are allowed at the R1 and R2 terminals. Refer to the
warnings in the Power Terminal Wiring and Power Connector Wiring
sub-sections in this document pertaining to these connections.
Protection Against Overloaded Brake Resistor
Required
It is essential that the external braking resistor be protected
against overload caused by a failure of the shunt/brake
control. The protection can simply open the circuit, such as a fuse or
overtemperature switch, or be wired to a contactor that isolates input
power to the actuator on an over temperature condition at the resistor. A
thermal switch built into the resistor assembly is best. Fuses are difficult
to size properly. A 3 to 5 amp, 250 V dual element time delay fuse is
usually sufficient. The purpose of the fuse to protect the resistor from
overheating not to protect the Tritex.
The resistor used must be rated for dynamic braking applications for
240 Vac drives, meaning it is capable of peak working voltage of at least
400V and can absorb high energy within a short period. The minimum
resistance is 40 Ohms. Recommended range is 40 to 50 Ohms. A higher
ohms value has no advantage and may not be able to keep up with peak
regenerative power, resulting in a high bus fault.
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