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Vol. 2.6 © 2020 Hanbell Precise Machinery Co., Ltd. All rights reserved
Liquid returned from motor:
In heat pump, VFD application, or low compression ratio system, the liquid refrigerant might
accumulate inside the motor casing. This is because in low compression ratio condition, the
pressure difference between Economizer (P
ECO
) and motor casing (P
motor
) is not enough to
cover the pressure drops in the piping line and the liquid refrigerant could accumulate in
motor casing. Auxiliary injection outlet should be connected to the evaporator to prevent
possible liquid flooding.
It is a must to install the auxiliary injection outlet in the working conditions below and use
angle valve to control the flow rate to the evaporator.
1.Low compression ratio: Working condition is CT-ET<15
℃
2.VFD system
：
Operational frequency is lower than 60%~80%of rated frequency
3. Heat pump system
Single-stage compression system (Without Economizer):
In single-stage compression system, the outlet of motor injection port is connected with
evaporator. The pressure in motor casing is similar to evaporating pressure and this will
cause condensation on the surface and deteriorate the insulation of main power terminals.
In addition, when the motor casing pressure is lower than bearing housing pressure, the
lubricant will flow into the motor casing and then enter the evaporator. Therefore, it is a
must to install MPV (Minimum Pressure Valve) in the main motor injection outlet pipes and
make sure to keep the standard below:
1kgf/cm
2
≦
Motor Pressure(P
motor
)
–
Evaporating pressure(P
s
)
≦
1.5kgf/cm
2
。
Temp. Sensors Pt100 or Pt1000 – for motor coil temp. monitoring
There are 4sets of Pt100 or Pt1000 temperature sensors mounted in the motor coil.
Adjust flow of liquid injection to motor by temperature feedback of these sensors. Choose
the highest temperature among these four sensors for controlling the motor coil
temperature between30~90
℃
.
Note: When temperature in any set of Pt100 or Pt1000 temp sensor reaches 90
℃
, the
controller should raise the alarm. When the temperature reaches 95
℃
, the
compressor should stop until the cause of high temperature has been eliminated.
Tmo> 90
℃
℃
℃
℃
alarm
Tmo> 95
℃
℃
℃
℃
shut down
Warning
：
Motor temperature after cooling should be higher than ambient temperature to
prevent condensing water which might cause insulation failure of wiring
terminals.
Protector connect method: 1 & 2 are PTC protector contact, A & B are concurrent, O1 is
contact for 2 pairs of Pt100, C& D are concurrent, O2 is contact for the other 2 pairs of
Pt100.
