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Vol. 2.6 © 2020 Hanbell Precise Machinery Co., Ltd. All rights reserved
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It is suggested to complete the accelerating time within 20 seconds for start-ups (0 to rated speed
time). Excessive accelerating time can easily lead to discontinuity of gear thrust which will
cause crash and bearing damage from slippage due to excessively low bearing loading. The
compressor will also stay longer in the surge zone.
2. Unloading: Frequency control in priority, when the frequency drops continuously to below (Z+1)
Hz into zone A, the compressor needs to start unloading. It is recommended that each decline
for IGV
≤
20% is 2%, for 20<IGV<50% is 5%,and for IGV
≧
50% is 8%.
3. Loading: When the frequency is increased to Z+2~3Hz, the compressor needs to start
increasing the loading. Load increment is recommended as mentioned above.
4. For a 60Hz VSD compressor, please apply Table 3.7 VSD compressor (50Hz) surge formula
and multiply the calculated value by 1.2.
VSD allowable operating range: as shown in Figure 3.7, the allowable operating range of a VSD
compressor is formed by the maximum operable capacity (105%), VSD surge formula and pressure
ratio, IGV opening and surge line.
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Surge line: Insert Z = 50Hz (fixed frequency), IGV opening (10-100%) into VSD surge formula,
the values of y (pressure ratio) obtained forms the surge line, alternatively, it can also be obtained
by using fixed frequency safety margin line formula.
Warning
：
：
：
：
The maximum operable frequency is the rated frequency of the compressor. Do not
overclock for higher compressor capacity. Overclocking to a critical speed will cause
structural collapse of high-speed shaft due to resonance.
Warning
：
The minimum operable rotational speed of the compressor is 60% of its rated speed.
Excessively low speed will cause inefficient discharge of motor cooling liquid, oil leakage
and bearing slippage due to low loading, in extreme cases, can lead to catastrophic
failure of compressor.
Figure 3.7 A schematic diagram of inverter operating range
