Control Of Mechanical Brake - Danfoss VLT AutomationDrive 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 frequency converter is unable to 'hold' the motor,
e.g. because of too big load. 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 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 frequency converter is brought into an alarm condition, i.e. over-voltage situation,
the mechanical brake immediately cuts in. This is also the case during safe stop.
Step-by-step Description
In hoisting/lowering applications, you need to be able to control an electro-mechanical brake.
For control of the mechanical brake any relay output or digital output (terminal 27 or 29),
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if necessary with a suitable magnetic contactor, may be used.
Make sure the output stays 'voltage-free' as long as the frequency converter is unable to drive the motor,
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for example due to the load being too heavy, or due to the fact that the motor has not been dismounted yet.
• Select Mechanical brake control [32] in par. 5-4* 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 frequency converter carries out a stop command.
NB!:
For vertical lifting or hoisting applications it is strongly recommended to ensure that the load can
be stopped in case of an emergency or a malfunction of a single part such as a contactor, etc.
If the frequency converter is in alarm mode or in an overvoltage situation, the
mechanical immediately brake cuts in.
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Introduction to FC 300
MG.33.B4.02 - VLT is a registered Danfoss trademark