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3-20 Basic Installation
MN1901
3.6 Regeneration resistor (Dynamic Brake resistor)
The 2.5A and 5A MintDrive
II
both have an internally fitted regeneration resistor *. For 7.5A,
15A, 20A and 27.5A MintDrive
II
, an external regeneration resistor must be installed to
dissipate excess power from the internal DC bus during motor deceleration. When
regeneration causes the DC bus voltage to rise by more than about 10-50 volts (model
dependent) above the maximum allowable DC bus voltage, the regeneration resistor is
automatically connected. When this happens, the yellow
DB On
LED on the front panel of the
MintDrive
II
will illuminate.
The MintDrive
II
has an additional emergency overvoltage trip system. However, this must not
be used as a means of protecting the drive from regeneration, since the trip occurs at a much
higher voltage than the regeneration switching voltage. Allowing regeneration to cause regular
overvoltage trips increases the chance of permanent damage to the MintDrive
II
.
Suitable regeneration resistors are listed in section A.1.9.
WARNING
: A regeneration resistor may generate enough heat to
ignite combustible materials. To avoid fire hazard,
keep all combustible materials and flammable vapors
away from the resistors. The regeneration resistor
should be mounted near the top of an enclosure to
maximize heat dissipation. Baldor regeneration
resistors are neither internally fused nor thermally
protected and, under extreme conditions, can cause
a fire hazard if not suitably protected or rated for the
application.
* If required by the application, additional external resistors connected to R1 and R2 will be
connected in parallel with the internal resistor.
3.6.1 Controlling regeneration
Some regeneration resistor assemblies include an overload switch to indicate when too much
power is being dissipated by the resistor. This switch can be wired to a digital input on the
MintDrive
II
. Using the Mint WorkBench Digital I/O tool, the input can be configured to be the
brake trip input. This allows the MintDrive
II
to respond to resistor overload conditions.
The Mint keyword
DBEXTTRIPINPUT
can also be used to configure a digital input for this
purpose. On three-phase MintDrive
II
models, the operation of the regeneration resistor can be
controlled by further Mint keywords. These also begin with the letters
DB
..., for example
DBEXTPEAKPOWER
. See the Mint help file for details.
Alternatively, a thermostatic switch on the regeneration resistor can be used to disconnect the
circuit breaker on the drive’s ACpower input. This will prevent the drive from operating if the
regeneration resistor overheats.
R1
R2
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