C6.2.38/0719/E
9
▪
Running the compressor below the envelope at low condensing temperatures is possible for no
longer than 30 minutes but users must be aware that unloading noise from the compressor can
occur.
▪
Fast speed changes can cause instable control, eg, on the superheat control. Per Emerson
experience speed changes should be in the range of 10 to 60 rpm/s depending on the system
reaction.
▪
The system controller should adequately take care of controlling the envelope.
▪
To stop the compressor, reduce the speed to 3000 rpm then stop the compressor
– see
Figure 7
"Controlled shutdown".
Before first start, each drive has to be set with the compressor model. This provides a speed-
dependent maximum torque protection related to the compressor model. The maximum torque
requirement will follow, with some margin, the maximum condensing temperature line for each
speed. If the torque exceeds the maximum torque allowed for a specific speed, the drive will reduce
the speed of the compressor in an attempt to keep the operating condition within the operating
envelope. If reducing the speed of the compressor does not bring the condensing temperature back
down within the envelope, the drive will go to the next level of protection and shut down the
compressor.
This drive feature aims to protect the drive and the compressor. It cannot be used in the system as
an operating envelope limitation.
The operating envelopes published in these guidelines are qualified for a minimum superheat of 10K.
The maximum superheat at high evaporating temperature should not exceed 20K.
NOTE: Operate matched pairs of compressor and drive combinations only.
NOTE: Before first start, each drive has to be configured according to the compressor model.
NOTE: The ED3 drive overload protection aims at protecting the drive and the compressor. It
cannot be used in the system as an operating envelope limitation. For more details on the
overload protection refer to
the Emerson User Manual for ED3.
2.6.7 Design features
The variable speed horizontal scroll YBVH* has a number of design features that improve efficiency
and reliability. An HVE-valve is part of YBVH* models for higher performance at high pressure ratio.
This valve prevents reverse rotation during shutdown; however, some shutdown sound may occur.
All YBVH* compressors are equipped with a positive displacement twin oil pump to ensure an
adequate supply of oil to the bearing system throughout the operating speed range of 1500 to
5500 rpm.
The motor in the variable speed scroll is a three-phase, brushless permanent magnet (BPM) design
coupled with a rotor embedded with high energy magnets. The input voltage is a series of +DC pulses,
spaced in time to create an alternating current frequency.
Summary of Contents for Copeland Scroll YBVH021 1U-3E9
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