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Vol. 2.6 © 2020 Hanbell Precise Machinery Co., Ltd. All rights reserved
5.3 Electrical data and design
5.3.1 Motor design
：
：
：
：
Y-
Δ
Δ
Δ
Δ
Starting
The Y-
Δ
motor connects the motor coil by Y connection during starting therefore
reducing voltage on coils to 1/
√3
of input voltage and reconnects the motor coil by
Δ
connection after starting. In doing so, starting current can be thoroughly decreased. It is
called voltage-drop starting.
The Y-
Δ
motor connection method is shown in the following motor wiring diagram: In Y
connection, MCM, MCS are inductive while the motor leads Z, X, Y are tied together as
neutral connecting as letter Y. After timer set period (till peak value decreases), MCM,
MCS become deductive. Around 0.25 sec later, MCM, MCD are inductive, they turn out
Δ
connection.
Full load Amper
Starting
Current
Time
I
(AMP)
Y- shift time 0.25~0.5sec
Figure 5.8Y-
Δ
starting diagram
Attention : After Y start, MCM & MCS are deductive for 0.25sec and then MCM & MCD
are inductive for
Δ
run. Within transient 0.25sec, a pseudo short circuit might occur due to
inappropriate action of contactors then causing compressor trip. When it occurs, we
recommend you use adjustable Y-
Δ
timer to lengthen the time span for MCM, MCS
deduction - MCM, MCD re-induct from 0.25sec to 0.5sec directly in the micro controller or
the PLC program. Please refer to Y-
Δ
shift time diagram for details. Because the motor is
not powered during Y-
Δ
shift. A shorter Y-
Δ
shift span is suggested to prevent the second
start due to decreasing rotation speed. However, if the Y-
Δ
shift span is too short, the
aforementioned pseudo short circuit might occur.
5.3.2 Characteristics of Starting
●
Y-
Δ
1. Starting current in Y connection is 1/3 of lock rotor ampere.
2. Starting torque in Y connection is 1/3 of lock rotor torque.
3. Acceleration of the motor rotor becomes smaller at full-load starting. Therefore
compressors require starting at partial load (=Actuator 0
％
).
●
Soft-start features
1. Starting current is 3 times higher of rated current ampere.
