E2 Motors and Motor Starting #2 Compressor Relays and Capacitors.

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


ΩΩΩR

UN

WIN

DIN

G

Split Phase Compressor Motor

R

STAR

T W

IND

ING

S

C

COM V/

VAC

DC


Starting a Split Phase Compressor

• Power must first go to both the run winding and the start winding


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


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


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


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


Two Types of Starting Relays

• Current Relays• Potential Relays


Current and Potential Relay


Current Relays

• Used on compressors under one horsepower

• Switch contacts are normally open (NO)• Relay coil energized by high starting

current


Current Relay


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.


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


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


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


2

1

MS

Current RelayJumper wire

Power InAlso used to connect

optional start capacitor

Relay CoilTo Main (Run)

Terminal

To Start Terminal


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


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


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


Capacitor Start Induction Run Motor (CSIR)

LINE


S C R

M S

CURRENT RELAY

L

STARTCAPACITOR


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)


Start Capacitor

Bleed Resistor 15,000 Ohms


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


Current Relay and

Overload


Current Relay and

Overload R

C

S


Terminals - Current Relays - Overloads

R

C

S L1

N

Jumper Wire

Remove jumper wire when installing start capacitor


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


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


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


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


Potential Relay Exposed

5

Relay CoilNormally Closed (NC) contacts between terminals 1 and 2

12


Normally closed contacts

Relay CoilDe-energized

Potential Relay – Normal Position


Potential Relay – After Start Up

Relay Coilenergized

Contacts 1 to 2 are pulled open


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


Potential Relay Capacitor Start Induction Run (CSIR) Motor

LINE


S C R

POTENTIAL RELAY

STARTCAPACITOR

5

2 1

Back EMF keeps the coil

energized


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


Potential RelayCapacitor Start-Capacitor Run (CSCR) Motor

LINE


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


Run Capacitors

• When the compressor is running, a run capacitor provides partial voltage to the start winding

• This lowers compressor amperage, increasing motor efficiency


Run Capacitors

Old style New Style


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


Permanent Split Capacitor (PSC) Compressor

Run WindingStart Winding

S C R

Run Capacitor

Line

Run Cap allows partial voltage to start winding


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


PTC Relays

• Positive Temperature Coefficient (PTC) solid state relays

• The resistance of the ceramic disc increases with temperature


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


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


PTC Relay and Run Capacitor

PTC Relay

Relay is wired in parallel with the

run capacitor


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


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


“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


Hard Start Kit (for PSC Compressor)

PTC Relay

Start Capacitor

Connect Leads to both sides of the RUN Capacitor


Power to Hard Start Kit

PTC Relay

Start Capacitor Incoming power

on start up

Full power plus start capacitor to start winding


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


Hard Start Kit Added to PSC Compressor

• The following slide shows the start kit in the starting circuit


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


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


Electronic potential relay start kits

Replacement RelaysReplacement Relays

Hard Start Kit


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


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


Solid State Current Relay Kits

• Useful on small hermetic refrigeration compressors

• Replaces the current relay and capacitor


Start Kit for Small Refrigeration Units

PTC Relay

Start Capacitor

Incoming Power

To RUN terminalTo START terminal


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


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


Start Kit with Overload

• Some kits include an overload• This kit can replace all the starting

components at one time


Electronic current relay start kit

Power Leads

Terminal connections for Run, Start, &

Common


Inside a “3 in 1” Kit

PTCR

S R

C

StartCapacitor

N

L1

PTCR

OVERLOAD

E2 Motors and Motor Starting #2 Compressor Relays and Capacitors.

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Transcript of E2 Motors and Motor Starting #2 Compressor Relays and Capacitors.