Control Of Mechanical Brake - Danfoss FC 300 Design Manual

FC 300 Design Guide

Control of Mechanical Brake

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For hoisting applications, it is necessary to be able to control an electro-magnetic brake. For controlling the
brake, a relay output (relay1 or relay2) or a programmed digital output (terminal 27 or 29) is required.
Normally, this output must be closed for as long as the adjustable frequency drive is unable to 'hold' the
motor, e.g., because of load that is too large. In par. 5-40 (Array parameter), par. 5-30, or par. 5-31 (digital
output 27 or 29), select mechanical brake control [32] for applications with an electro-magnetic brake.
When mechanical brake control [32] is selected, the mechanical brake relay stays closed during the start
until the output current is above the level selected in par. 2-20 Release Brake Current. During stop,
the mechanical brake will close when the speed is below the level selected in par. 2-21 Activate Brake
Speed [RPM]. If the adjustable frequency drive is brought into an alarm condition, i.e., an overvoltage
situation, the mechanical brake immediately cuts in. This is also the case during safe stop.
Step-by-step Description
In hoisting/lowering applications, it must be possible to control an electro-mechanical brake.
To control the mechanical brake, any relay output or digital output (terminal 27 or 29)
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can be used; if necessary use a suitable magnetic contactor.
Ensure that the output stays voltage-free as long as the adjustable frequency drive is
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unable to drive the motor, for example, due to the load being too heavy or due to the
fact that the motor has not yet been dismounted.
• Select Mechanical brake control [32] in par. 5-4* (or in par. 5-3*) before connecting the mechanical brake.
The brake is released when the motor current exceeds the preset value in par. 2-20.
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The brake is engaged when the output frequency is less than the frequency set in par. 2-21 or
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2-22 and only if the adjustable frequency drive carries out a stop command.
NOTE
Check that the brake resistor is rated for 410 V (240 V units), 820 V (480 V units), 850 V (500
V units) or 975 V (600 V units) - unless Danfoss brake resistors are used.
NOTE
Do not touch the brake resistor since it can get very hot during/after braking.
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Introduction to FC 300
MG.33.B6.22 - VLT is a registered Danfoss trademark