Eaton Cutler-Hammer AF91 Operation And Service Manual

INTRODUCTION
The Dynamic Brake kit consists of a compact externally mounted dynamic brake module that monitors the DC bus voltage
and AC line voltage of a variable frequency drive. The theoretical DC bus voltage should never exceed 1.414 times the AC
line voltage. Should the DC bus voltage exceed this value, the dynamic brake module will bleed energy off of the DC bus by
placing a resistor across the bus at a variable duty cycle. As the DC bus level increases above the threshold level, the width
of the pulses increases to bleed more energy per second off of the DC bus. As the AC line voltage changes, the dynamic
brake module threshold level will automatically change to keep the threshold level at 1.41 times 1.1 times the AC line voltage.
WARNING: Do not service equipment with either AC and/or DC voltage applied. Unit can be the source of fatal electrical
shocks! To avoid shock hazard, disconnect AC and DC power and allow DC bus to decay completely before working on
controller. Warning labels (not supplied) must be attached to terminals, enclosure and control panel.
INSTALLATION
Proper location of the dynamic brake unit is necessary to achieve specified performance and normal lifetime operation. The
dynamic brake unit should always be installed in an area where the following conditions exist.
• Ambient operating temperature.
Enclosed Unit: -10 to 40°C
Chassis Unit: -10 to 50°C
• Protected from rain and moisture.
• Shielded from direct sunshine.
• Free from metallic particles and corrosive gas.
• Free from oil, grease and liquid.
• Free from massive vibration.
• Free from high electromagnetic radiation.
• Free from radioactive material.
• Free from flammable material.
• Installation of the dynamic brake unit must be oriented so that the front side of the unit faces front and the top of the unit is
directed upward for maximum heat dissipation.
• Mounting of the dynamic brake unit must be to a non-combustible panel.
Note: The heatsink may heat up to above 100°C during maximum braking. Warning labels (not included) should be
installed warning personnel of the high temperature of the heatsink.
AF91 EXTERNAL DYNAMIC BRAKE KIT
OPERATI0N and SERVICE MANUAL