e2 motors and motor starting #2 compressor relays and capacitors
TRANSCRIPT
E2 Motors and Motor Starting
#2 Compressor Relays and Capacitors
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 2
Single Phase Compressor Starting
• Single phase compressors have a start winding and a run winding
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 3
ΩΩΩR
UN
WIN
DIN
G
Split Phase Compressor Motor
R
STAR
T W
IND
ING
S
C
COM V/
VAC
DC
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Starting a Split Phase Compressor
• Power must first go to both the run winding and the start winding
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Split-Phase Compressor Motor Starting
LINE
RUN WINDING
START WINDING
C RS
Power is needed for the motor to run
Power is also needed to start
Once started, the start windings are removed from the circuit
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Start Relays
• A relay is used to energize the start winding
• The same relay is also used to take the start winding out of the circuit
• The next slide is a diagram of where start components are located in a compressor motor circuit
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Diagram of Compressor Start Components
C
RS
N L1For the motor to run, power is needed to Common and Run
For the motor to start, power is needed to the Start terminal.
Add torque with a Start Capacitor
After start up, A Start Relay opens the circuit
STARTRELAY
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Types of Compressor Starting
• RSIR: Resistance start, induction run– Uses a start relay only
• CSIR: Capacitor start, induction run– Uses a start relay and start capacitor
• CSCR: Capacitor start, capacitor run– Uses a start relay and both start and run
capacitors
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Two Types of Starting Relays
• Current Relays• Potential Relays
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Current and Potential Relay
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Current Relays
• Used on compressors under one horsepower
• Switch contacts are normally open (NO)• Relay coil energized by high starting
current
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Current Relay
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Motor Amp Draw on Start up
• Current relays respond to amp draw• Relay contacts close on high starting current • Relay contacts open as amperage drops
60A
40A
20A
0A
20% 40% 60% 80% 100%Motor Speed
LRA
Start Up RLA
Am
per
ag
e D
raw
Motors draw high amps (LRA) on start up.
Amperage drops as speed increases.
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Starting with a Current Relay
• Current relays are used on refrigeration systems with fixed metering devices
• When system pressures are equalized only a relay is needed to start the compressor
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Split Phase Motor with Current Relay
LINE
RUN WINDINGSTART WINDING
S C R
M S
CURRENT RELAY
L
POWER ON
1- High starting amps energize relay coil, close contacts
2- Line voltage goes to start windings
3- Motor speed increases, amperage decreases, relay coil allows contacts to open
4- Start Winding drops out
5- Motor continues to run, drawing normal current
Original Diagram from Copeland Handbook
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How a Current Relay Works
• The drawing on the next slide shows how the start winding is energized, then how it is taken out of the circuit
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2
1
MS
Current RelayJumper wire
Power InAlso used to connect
optional start capacitor
Relay CoilTo Main (Run)
Terminal
To Start Terminal
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Energize Start and Run Windings
Voltage ready for Start Winding
Power to Main (RUN) Winding
Voltage through coil
High starting current increases coil magnetism
Plunger is pulled up
Contacts close
Power to Start Winding
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Start winding de-energized
No voltage to Start Winding
Power to Main (RUN) Winding
Power to Start Winding
As motor speed increases, amperage falls
Plunger falls
Plate falls, contacts open
Compressor continues running
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Adding a Start Capacitor
• A refrigeration system with a TEV requires more starting torque
• Adding a start capacitor in series with the start winding is all that is needed
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Capacitor Start Induction Run Motor (CSIR)
LINE
RUN WINDINGSTART WINDING
S C R
M S
CURRENT RELAY
L
STARTCAPACITOR
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Start Capacitors
• They provide more phase shift to the start winding
• Start capacitors are designed to be in the circuit for only a few seconds
• A resistor quickly bleeds off capacitor charge to prevent excessive arcing across the relay contacts
• Note: Always replace capacitors with the same microfarad rating (MFD or µF) and equal (or greater) volt amp capacity (VAC)
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Start Capacitor
Bleed Resistor 15,000 Ohms
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Terminal box on a small compressor
• A current relay plugs into the start and run terminals
• The external overload is mounted inside the terminal box
R
C
S
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Current Relay and
Overload
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Current Relay and
Overload R
C
S
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Terminals - Current Relays - Overloads
R
C
S L1
N
Jumper Wire
Remove jumper wire when installing start capacitor
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Two-wire Overload
• Single phase overloads are usually in the common wire
• Its bimetal disk warps when heated• It responds to motor heat and amperage
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2-wire bimetal overload
3
21
L1
Normal operating condition: 1-2 closed
If the load draws high current, the heater from 2-3 becomes hot
Load
This warps bimetal 1-2, and opens the circuit between 2 and the Load
Power on
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Potential Relays
• Used for starting single phase compressors up to five horsepower
• Contacts are normally closed (NC)• The relay coil is energized by Back EMF
(electromotive force) generated in the start winding
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2
51 C
“Dummy” terminal
Potential Relay – Top View
Solenoid Coil
Contacts
R
From common terminal
From run terminal
To start terminal
S “Dummy” terminal
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Potential Relay Exposed
5
Relay CoilNormally Closed (NC) contacts between terminals 1 and 2
12
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Normally closed contacts
Relay CoilDe-energized
Potential Relay – Normal Position
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Potential Relay – After Start Up
Relay Coilenergized
Contacts 1 to 2 are pulled open
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Potential Relays in Operation
• The normally closed contacts allow full voltage to the start winding
• The relay coil is energized• The contacts open• Back EMF keeps the coil energized, which
keeps the contacts open
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Potential Relay Capacitor Start Induction Run (CSIR) Motor
LINE
RUN WINDINGSTART WINDING
S C R
POTENTIAL RELAY
STARTCAPACITOR
5
2 1
Back EMF keeps the coil
energized
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Adding a Run Capacitor
• A run capacitor is added to the starting circuit
• When the potential relay opens the run cap stays in the circuit
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Potential RelayCapacitor Start-Capacitor Run (CSCR) Motor
LINE
RUN WINDINGSTART WINDING
S CR
POTENTIAL RELAY
STARTCAPACITOR
RUN CAPACITOR
Back EMF keeps the coil
energized
The run capacitor stays in the circuit for greater
motor efficiency
5
2 1
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Run Capacitors
• When the compressor is running, a run capacitor provides partial voltage to the start winding
• This lowers compressor amperage, increasing motor efficiency
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 40
Run Capacitors
Old style New Style
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 41
Run Capacitors on PSC Compressors
• No start relay is used on PSC motors• A run capacitor is permanently wired into
the start windings• PSC compressors are used on fixed
metering device air conditioning systems, where pressures equalize during the off cycle
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Permanent Split Capacitor (PSC) Compressor
Run WindingStart Winding
S C R
Run Capacitor
Line
Run Cap allows partial voltage to start winding
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SC
R
PSC* Compressor with Run Capacitor
Compressor
Partial voltagethrough run cap
*Permanent Split Capacitor
Compressor starts and runs
efficiently
Energize startwinding
LINE
Run Capacitor
CRS
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PTC Relays
• Positive Temperature Coefficient (PTC) solid state relays
• The resistance of the ceramic disc increases with temperature
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Run Start
P.T.C. Relay Cutaway
Power from Run terminal
Ceramic Disk
Power to Start terminal
Wire spring holds disk and serves as a conductor
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Location of the PTC Relay
• The relay is wired in parallel to the run capacitor
• It allows full voltage starting, then drops out of the circuit
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PTC Relay and Run Capacitor
PTC Relay
Relay is wired in parallel with the
run capacitor
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PTC Relay in Operation
• When cool, the disk allows full voltage to the start winding
• The disk heats up quickly, stopping the flow of voltage
• Power then takes the path of least resistance through the run cap to the start terminal
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 49
SC
R
Start Assist with PTC* Relay
CompressorRun Capacitor
PTC Relay
Starts withfull voltage
to start winding
Runs withpartial voltage
through run cap
*Positive Temperature Coefficient
Voltage stops when relay heats
LINE
RC
SS
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“Hard Start” Kits
• Used on air conditioning compressors when compressor has trouble starting
• Contains a solid state relay and start capacitor
• Installed parallel to the run capacitor
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Hard Start Kit (for PSC Compressor)
PTC Relay
Start Capacitor
Connect Leads to both sides of the RUN Capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 52
Power to Hard Start Kit
PTC Relay
Start Capacitor Incoming power
on start up
Full power plus start capacitor to start winding
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Hard Start Kit Out of the Circuit
PTC Relay
Start Capacitor
PTC Relay heats up
Current flow stops
Incoming power now goes through
RUN cap
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Hard Start Kit Added to PSC Compressor
• The following slide shows the start kit in the starting circuit
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 55
SC
R
PSC Compressor Start Assist
LINE
PSC Compressor
Hard Start Kit(PTCR & Start Cap)
CS
Full Power plusStart cap to Start
PTCR heats up,Stops current flow
Current now goes through
only the run cap.
Run Capacitor
RS
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Solid State Potential Relays
• Use only if the OEM (Original Equipment Manufacturer) potential relay is not available
• Use only as a temporary replacement of OEM potential relay
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 57
Electronic potential relay start kits
Replacement RelaysReplacement Relays
Hard Start Kit
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 58
Diagram of SS Potential Relay
• OEM potential relay coils operate on Back EMF
• Solid state potential relay coils operate on time to open the start circuit
• The wiring hookup is basically the same as the original relay
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Electronic Start Relays (Universal replacement relay PRO-90 by SUPCO)
5
41
2
6
R S
CO.L.
NRunCap
StartCapRun cap provides
efficient running
L1
Run Cap acts like a jumper wire
Timer opens 1-2
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Solid State Current Relay Kits
• Useful on small hermetic refrigeration compressors
• Replaces the current relay and capacitor
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Start Kit for Small Refrigeration Units
PTC Relay
Start Capacitor
Incoming Power
To RUN terminalTo START terminal
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Installing a Start Kit
• The following slide shows how the start kit is hooked up to the compressor
• Use the original overload, NEVER jump out the overload
Note: This kit can be used even if the original compressor did not have a start capacitor
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Replacing a Start Relay with a Start Kit
Remove RelayConnect L1 & Run
L1
Connect to StartUse existing
overload
Start Compressor
PTC Relay&
Start Capacitor
N
L1
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Start Kit with Overload
• Some kits include an overload• This kit can replace all the starting
components at one time
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 65
Electronic current relay start kit
Power Leads
Terminal connections for Run, Start, &
Common
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 66
Inside a “3 in 1” Kit
PTCR
S R
C
StartCapacitor
N
L1
PTCR
OVERLOAD
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2 67