70
1. Limitation of supply power
a. Voltage limitation
Long term running : rated voltage ±5%
Instant running : rated voltage ±10%
b. Frequency : Rated frequency ±2%
Note that in the region where the electricity power is unstable, install an additional Hi-Low voltage protector
with ± 5% under and over tolerance outside the normal voltage to ensure the safe running of the compressor.
2. Unbalanced voltages :
Unbalanced voltages usually occur because of variations in the load. When the load on one or more of the
phases is different than the other(s), unbalanced voltages will appear. This can be due to different
impedances, or type and value of loading on each phase. Unbalanced voltages can cause serious problems,
particularly to motor.
NEMA defines voltage unbalance as follows :
Percent voltage unbalance = 100 x
NEMA states that polyphase motors shall operate successfully under running conditions at rated load when
voltage unbalance at the motor terminals does not exceed 1%. Further, operation of a motor with above a 5%
unbalance condition is not recommended, and will probably result in damage to the motor.
Unbalanced voltages at motor terminals cause phase current unbalance ranging from 6 to 10 times the
percent voltage unbalance for a fully loaded motor. This causes motor over current resulting in excessive heat
that shortens motor life, and hence, eventual motor burnout. If the voltage unbalance is great enough, the
reduced torque capability might not be adequate for the application and the motor will not attain reated speed.
Some of the more common causes of unbalance voltages are :
Unbalanced incoming utility supply
Unequal transformer tap settings
Large single phase distribution transformer on the system.
Open phase on the primary of a 3 phase transformer on the distribution system
Faults or grounds in the power transformer
Open delta connected transformer banks
A blow fuse on 3 phase bank of power factor improvement capacitors
Unequal impedance in conductors of power supply wiring
Unbalanced distribution of single phase loads such as lighting
Heavy reactive single phase loads such as welders
An 3 phase unbalanced voltages protector is upon request as optional accessory. Please contact with Hanbell
(maximum voltage deviation from average voltage)
(average voltage)
Summary of Contents for RC2-F Series
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