Electrical Data And Design; Motor Design - Hanbell RC2-F Series Manual

5. Electrical data and design

5.1 Motor design

HANBELL RC2-F series screw compressors are fitted with Y-Δ motor as standard. But Δ/ΔΔ motor (Part Winding
Starting – PWS) is also available for model RC2-100F ~ RC2-580F.
i.e.
● RC2-100F ~ RC2-580F both Y-Δ motor and Δ/ΔΔ motor are available.
● RC2-620F ~ RC2-1530F only Y-Δ motor are available.
Y-Δ Starting
Y-Δ motor connects motor coil by Y connection during starting therefore reducing voltage on coils to 1/√3 of input
voltage and reconnects motor coil by △ connection after starting. By doing so, we can decrease starting current
thorough voltage drop, i.e., so-called voltage-drop starting.
In Y connection, MCM、MCS are inductive while motor leads Z,X,Y are tied together as a neutral connecting as Y
fashion. A few seconds later ( 3 ~ 5 sec is recommended), MCM, MCS become deductive. Around 0.25 sec later,
MCM,MCD are inductive，it turns out △ run connection. Y-Δ motor connection method is shown in the following
motor wiring diagram:
Please pay attention : After Y start，MCM & MCS are deductive for 0.25msec and then MCM & MCD are inductive
for Δ run. Within as transient as 0.25msec, pseudo short circuit might occur due to inappropriate action of
contactors, causing trip of compressors. When it occurs, we recommend usage of adjustable Y-Δ dedicated Timer
or slightly lengthen span of time for MCM, MCS deduction - MCM,MCD re-induction from 0.25 msec to 0.5 msec
max directly in micro controller or PLC program. Please refer to Y-Δ shift time diagram for details. Because motor
is not powered during Y-Δ shift, shorter Y-Δ shift span is suggested to prevent second start due to decreased
rotation speed. However, if Y-Δ shift span is too short, aforementioned pseudo short circuit might occur.
I
(AMP)
Starting Current
Y-
67
Full load Amper
Time
shift time 0.25~0.5msec