NORD Drivesystems B1000 - Manual (Page 735)

www.nord.com G733
General
Information
BRAKES
G1000 – Subject to Change Without Notice
GVE/GHE/GPE GVE/GHE/GPE
AC BRAKE AC BRAKE
VOLTAGE VOLTAGE
GPU GPU
AC Switching (Standard Stopping)
The rectifi er can be wired to operate by supplying
and removing AC power, commonly called AC
switching. The advantage to using AC switching is
that the rectifi er can be powered directly from the
motor’s terminal block and no additional wiring
is required. However, tapping into the motor’s
terminal block gives the slower stopping time due
to the de-energizing time of the motor’s magnetic
fi eld. The stopping time can be improved by wiring
the rectifi er from an external power supply.
DC switching (Fast Stopping)
DC switching directly interrupts the current fl ow in
the DC circuit of the rectifi er. This provides much
faster stopping, because you do not need to wait
for the motor’s magnetic fi eld to de-energize. To
implement DC switching, a normally open relay
must be installed between terminals 3 and 4 on
the rectifi er for rectifi er types GVE, GHE, and GPE.
For GPU type rectifi ers simply remove the jumper
between terminals 3 & 4 to activate DC switching.
GP... High Performance Rectifi ers
The “GP…” high performance rectifi ers improve
brake release time and stopping time. The “GP….”
rectifi er is a push-hybrid rectifi er; meaning that it
initially acts as a full-wave rectifi er for approximately
250 ms, after which it operates as a half-wave rectifi er.
There are two types of “GP…” rectifi ers. The fi rst
type utilizes External DC Switching “GPE...”, this
is primarily used in across-the-line applications,
where the brake power is supplied from the motor
terminal block. The second type utilizes Integrated
DC Switching “GPU...”. The built-in DC switching of
the “GPU” rectifi ers is supply voltage triggered. The
“GPU” rectifi ers can only be used when the brake
is powered separately from the motor. Examples
include using a frequency inverter, two-speed
motor or soft-starter. The “GPU” rectifi ers are not
suitable for use when the brake power is taken form
the motor supply power (motor terminal block).
There are two ways to apply “GP…” rectifi ers. The
fi rst is called, “overexcitation (fast brake release)”
and the second is called, “reduced power holding
(very fast stopping)”
Overexcitation (fast brake release)
In overexcitation, the rectifi er initially over-voltages
(overexcites) the brake coil, causing a stronger than
normal magnetic fi eld which releases the brake quicker
than normal. The rectifi er then is switched to a lower
holding voltage so it does not thermally overload the
brake coil. In this method, the brake coil is selected as
if the brake system is powered by a half-wave rectifi er.
In other words, the DC brake voltage should be 45%
of the applied AC rectifi er input voltage. This brake
control is also sometimes referred to as “Voltage
Forcing” or “Supercharging”.
Overexcitation is commonly used in very high cycling
brakemotor applications to reduce motor heating
during the motor start and brake release.
Reduced Power Holding (very fast stopping)
In reduced power holding, the rectifi er initially
supplies the rated DC voltage to the brake coil. When
voltage is fi rst applied, the rectifi er operates as a
full-wave rectifi er (90% of the applied AC voltage),
releasing the brake in the standard time. After the
brake is released, the rectifi er switches to half-wave
mode (45% of the applied DC voltage), weakening the
brake’s magnetic fi eld. The weaker fi eld will allow the
brake to stop more quickly when power is removed.
In this method the brake coil is selected as if the brake
system is powered by a full-wave rectifi er. Therefore,
the brake coil’s DC voltage rating should be 90% of
the AC voltage applied to the rectifi er.
GPE - High Performance Rectifi er
with External DC switching
Nomenclature Part # Type Color
GPE20L 19140230 Push-hybrid Black
GPE40L 19140240 Push-hybrid Black
GPU - High Performance Rectifi er
with Integrated DC switching
Nomenclature Part # Type Color
GPU20L 19140090 Push-hybrid Black
GPU40L 19140170 Push-hybrid Black