VYPER
™
VARIABLE SPEED DRIVE
MAINTENANCE
100-210 IOM (
JUL
09)
Page 58
FREQUENTLY ASKED QUESTIONS
All service on this equipment should
be performed by Johnson Controls
certified service personnel only.
Death, severe personal injury, and/or equipment damage
may occur if service is not performed by competent
personnel.
Why don’t the measured input amps shown on the
Quantum
™
Lx control panel agree with the rated FLA?
The input current to the Vyper
™
may be considerably lower
compared to the output current. This is due to the power factor
at the input to the Vyper
™
being greater than 0.95 and nearly
unity when the Harmonic filter option is included. Motor FLA
must be measured at the motor terminals, where the power
factor is the normal motor power factor. Use the true RMS
reading meter to make the measurements.
On the Remote-mounted Vyper
™
compressor drive, what
is the dV/dt “snubber” filter for?
The combination of long runs of wire between the Frick
Vyper
™
and the compressor motor with the fast rise time
of the output voltage of the Vyper
™
can cause excessively
high voltage potential at the motor terminals. Without the
dV/dt filter, the insulation in the motor terminal can be overly
stressed. The dV/dt network reduces the high voltage mo-
tor potential to below the motor’s voltage specification. The
design of the dV/dt network has a requirement to be added
to the top of the motor terminal box. No additional wire may
be added between the dV/dt network and the motor terminal
connections. The addition of wire reduces the dV/dt network’s
effectiveness and potentially shortens the life of the motor.
What is the proper wire sizing for a Frick Vyper
™
drive?
The input power wires are sized at 1.25 times the full load
amps of the compressor motor, plus oil pump amperage and
control transformer amps.
How is a 12-lead motor connected to the Vyper
™
?
Most of the 12 lead motors actually have two sets of parallel
windings, and therefore have two ones, two twos, etc. The
Vyper
™
is connected to the motor in the delta configuration,
which means that leads are paired 1 and 6, 2 and 4, and 3
and 5. The T1 lug in the Vyper
™
will then have two 1s and
two 6s attached to it.
Some motors, which were produced in the past, were labeled
as 1 through 12. These motors had the first set of wires
marked 1 to 6. Numbering then continued with the second
1 marked as 7, 2 numbered as 8, so on up to 12. Take the
second set of numbers above six, subtract 6 from the number
and relabel the result.
What is the peak input voltage value?
The displayed value is the phase to neutral voltage at the
input to the drive in terms of peak voltage, as measured by
an oscilloscope.
Phase to neutral is normally the phase-to-phase voltage
divided by the square root of three, or 265 VAC phase to
neutral, for a 460 VAC system. The peak value of the 265 VAC
measurement is approximately that number times the square
root of two.
When is a booster pump required on a Vyper
™
compres-
sor drive?
The Frick Vyper
™
requires eight (8) foot of head for proper
coolant flow (water or glycol) to the heat exchangers. If this
amount of head is not available, then a booster pump provid-
ing at least 10 or 15 foot of head is required.
The pink color of the coolant has faded. Is there a prob-
lem?
The coolant normally has a pink or rosy color when new. After
months of operation, this color may dissipate, and the coolant
may appear almost colorless. The lack of color in the cool-
ant does not necessarily indicate a problem. Most colorless
samples test above 1000 PPM nitrite, which is normal. There
is no need to flush the system unless the coolant becomes
opaque or cloudy. If this is the case, please obtain a sample for
analysis, then flush the system with coolant and install fresh
coolant. Be aware that cloudy coolant may contain bacteria.
Use adequate preventative procedures to avoid contamination.
Change the coolant annually, regardless of color.
Why is the Vyper
™
circuit breaker tripping?
Circuit breaker tripping is normal for a failed Vyper
™
drive. The
unit does not have input fuses. The AC choke now reduces
the current flowing to the short and the circuit breaker is fast
enough to provide proper protection. A tripped circuit breaker
may be due to a shorted condition inside the drive, the pres-
ence of a ground fault condition, or due to the breaker itself
being faulty. Check for shorts at the input and output of the
drive. Check for leakage current to ground. If no leakage is
found, try raising the adjustable thresholds on the breaker. The
breaker is likely to be defective if tripping continues to occur.
What is the test button on the Vyper
™
Logic board?
When the Vyper
™
is not running, the test button (Callout 1,
Figure 73) may be used to test operation of the logic outputs
to the Vyper
™
power module, as well as the operation of the
gate driver board on the IGBT module. When the button is
depressed, six output LEDs on the Logic Board alternately
light the three plus (+) LEDs then the three (–) LEDs. At the
same time, six LEDs on the gate driver board will alternate
between dim and bright intensity. Several conditions can
inhibit this test function:
•
If any VSD fault exists.
•
If the unit is in precharge.
•
If the SCR trigger is enabled.
•
If the VSD unit is running.
•
A 4-minute timer is part of this function to ensure that the
DC Link Voltage is discharged to a safe level. This timer
must time-out before the Test Button will function.
Figure 73 - Logic Board Test Button
