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lower voltage (and thus lower current) to the motor during starting.
� Part winding �Some motors have multiple windings that allow an incremented start.
� Series resistor or reactor �These devices limit the initial current, and are switched out at some point in the starting process.
� Wye-Start, Delta-Run �Motors capable of both Wye and Delta operation can be configured as Wye to start and Delta to run.
Today, however, when people talk about soft start, they usually mean the kind of programmable soft start that solid-state soft starters make possible. These devices utilize silicon controlled rectifiers (SCRs), thyristors, or other power semiconductors to control the voltage and current supplied to the motor during the starting process. They are available in 3-phase and single-phase models, in voltages from 115 to 575 volts (a few even higher), and for motors up to 700 hp. Different models exhibit different characteristics, but two primary modes of operation are the current limit and current ramp modes. Referring to the graph once again, curve 2 illustrates the first mode and curve 3 the second.
Having said this, the softstarter's main function with scroll compressors is the reduction of the inrush current during startup. Via a Direct on line start, currents may reach 6 to 7 times (pr more) the nominal compressor current which is undesirable (voltage dips, light flickering, higher energy contracts etc)and sometimes utility regulations do not permit to go above a certain level of current during start.
Softstarters can also have integrated bypass relays which are activated as soon as soon as the compressor reaches its running speed. In this way, there are minimal heat losses on the softstarter and the compressor runs freely at its rated speed. Once at rated speed, the compressor noise is minimal. In fact, such compressors are used in domestic heat pumps all over Europe.
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| Company: |
Soft Starter Manufacturers
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| Contact: |
Mr. Frank Chang |
| Address: |
Building 2 Xuwu Gongle Xixiang, Bao'an District |
| Postcode: |
518000 |
| Tel: |
8675528480235 |
| Fax: |
8675528480233 |
| E-mail: |
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