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Example
If an unloaded E34 motor (rotor inertia = .035 oz-in-sec
rotating at 1500 rpm, the stored energy is:
If all this energy is transferred to a 6800 mf capacitor, initially
charged to 70 volts, the voltage on the capacitor after the transfer
is equal to 76 volts.
Note: This exceeds the volt maximum specification of the 6415
drive.
In practice, most or all the kinetic energy is dissipated in the
motor windings or in the drive power circuitry so that voltage
pump-up is often not a problem. However, in systems running at
high speeds and having large load inertia, the voltage might be
pumped up significantly and circuitry must be added to insure
that the 75 volt limit is never exceeded.
Note: Regeneration effects should be considered in the presence
of high line conditions.
To find out if regenerative energy is a problem, run the system
while monitoring the supply voltage with a storage oscilloscope.
Alternatively, a simple peak detector made form a diode and a
capacitor can be attached to the bus and the peak voltage
measured using a digital voltmeter. Start the system with slow
deceleration rates and monitor the motor power supply to see if
the voltage rises during deceleration. Slowly increase the
deceleration rate (shorten the deceleration time) while monitoring
the voltage. If regeneration causes the supply voltage to exceed
75 Vdc peak, a clamping circuit is required.
Note: Be sure to consider the effect of high line voltage when
evaluating this test.
C - 8
-5
3.87 * 10
* .035 * 15002 = 3.0 joules
6415 Installation & Hardware Reference Manual - Rev E
2
) is
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