Single compressors
Electrical data, connections and wiring
The CDS803 frequency converter generates by
design a compressor soft start with an default
initial ramp up of 7.5s to 50 rps.
Current inrush will not exceed the frequency
converter maximum current.
Basically seen from the mains the inrush peak
reach a level which is only a few percent more
than the rated nominal current.
Soft-start control
The compressor will only operate properly in a
single direction. If electrical connections are done
correctly between the drive and the compressor
terminals (compressor and drive terminals U, V &
W matching), the drive will provide correct phase
supply to the compressor, and reverse rotation
will be not possible:
• CDS803 terminal U (96) to VZH terminal T1/U
• CDS803 terminal V (97) to VZH terminal T2/V
• CDS803 terminal W (98) to VZH terminal T3/W
If compressor and drive U, V & W terminals are
not matching, the compressor can operate in a
reverse rotation. This results in excessive noise,
no pressure differential between suction and
discharge, and suction line warming rather than
immediate cooling. The compressor can be
rapidly damaged in these conditions. To protect
compressors from reverse rotation, one of below
actions is required:
- Use pressure sensors to monitor pressure
difference between discharge and suction of
the compressor, and for normal operation,
discharge pressure should be at least 1 bar
higher than suction pressure within 30 s
running after compressor starting.
- Apply the dome temperature sensor on top of
the compressor upper shell to sense the high
temperature resulted from compressor reverse
run and trigger the alarm in system controls.
Mains connection to the CDS803 frequency
converter order has no influence on the output
phase sequence which is managed by the
frequency converter.
The compressor terminal box IP rating according to IEC529 is IP22.
VZH scroll compressors are not equipped with
an internal motor protector. Motor protection
is provided by the variable speed drive. All
parameters are factory preset in order to
guaranty locked rotor or overload current
protection.
When a warning situation is reached in the
current control, the CDS803 frequency converter
will automatically reduce the compressor
speed in order to keep the motor current of the
compressor below the maximum allowed.
In some cases when compressors stop under
low mass flow low speed condition, discharge
valve may not seal discharge port fast enough,
thus compressors may run in a reverse rotation
due to the residual pressure difference and
generate a big noise. Running in the wrong
direction will reduce the reliability and lifetime
of the compressor. The drive shall prevent the
compressors scroll set from running the wrong
way during stop with anti reverse protection.
To activate the function, the customer must be
able to enable and disable the ANTI-REVERSE
PROTECTION.
Phase sequency and
reverse rotation
protection
IP rating
Motor protection
Anti-reverse protection
Element
Numerals or letters
Meaning for the protection of equipment
First characteristic
numeral
0
1
2
3
4
5
6
Against ingress of solid foreign objects
(non protected)
≥ 50 mm diameter
≥ 12.6 mm diameter
≥ 2.5 mm diameter
≥ 1.0 mm diameter
dust protected
dust tight
Second
characteristic
numeral
0
1
2
3
4
5
6
7
8
Agains ingress of water with harmful effects
(non protected
vertically dripping
dripping (15° tilted)
spaying
splashing
jetting
powerful jetting
temporary immersion
continuous immersion
22
FRCC.PC.034.A2.02
Application Guidelines
