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Understanding ECM Motors
What does ECM mean?
Electrically Commutated Motor
The ECM Technology
The GE ECMTM motor is a brushless DC, Three - phase
motor with a permanent magnet rotor. Motor phases are
sequentially energized by the electronic control, powered
from a single-phase supply.
Control Construction
• Microcomputer module
• Power Conditioning module
• Encapsulated with a polyurethane
compound to protect against moisture
Stator Construction
• Laminated, interlocked stator
• Steel shell, aluminum end shield,
through-bolt construction
• Inslot Salient wound
• Available in closed, partial, or fully
vented shell
Rotor Construction
• 3 Iron Ferrite magnets glued on rotor sleeve
• Magnetized at GE Factory
• Two Resilient Rings isolate the shaft from the rotor
• Ball Bearings
ECM Modes of Operation Control Cont…
Thermostatic Control (TSTAT)...Most widely used in Residential systems
Discrete field selection of airflow settings and comfort options.
•
•
•
•
•
•
Direct 24 VAC interface to conventional thermostats
Supports 1 or 2 “stage” systems
Suitable for furnaces, heat pumps, and fan coils
4 levels of cooling airflow + trim
4 levels of heating airflow + trim
Enables use of 4 unique delay profiles
Connects to
Connects to
Thermostat
Tap Board *
* OEM Specific
Motor
Tap Boards
(or interface boards)
4 Field selectable outputs for:
Purpose:
Designed to convert one TSTAT input
into up to 4 different field selectable
outputs.
• Heating
• Cooling
• Trim multipliers
• Delay/Ramps
• May also be used to enable Humidistat
24 VAC
Input
Selection
Output
full wave
half wave half wave +
no signal
How the Tap Board Communicates with the ECM
24 VAC Input
Selection*
Output
full wave
D
half wave -
C
B
A
half wave +
no signal
* For Cool, Heat, Adjust, Delay
How is a PSC motor different than an ECM?
PSC
•
•
•
•
vs.
ECM
•
•
•
•
Start-up by contact to AC line
Controlled by AC line
Abrupt turn-on stress, noise
Motor speed taps are inefficient and
produce only minor speed adjustment
Permanently connected to AC line
Controlled by low voltage inputs
Motor starts softly, ramps to speed
Wide and efficient airflow range
between hi and low taps
Motor
ECM
PSC
AC Power
Relay
Contacts
AC Power
Inverter
Power
Conditioning
AC to DC
Conversion
Motor
Interface
Control
HVAC System Control
Start / Run
Capacitor
INPUTS
24Vac
Compressor
low /hiCalls
/ off
Constant Fan
Heat Calls
low stage
hi stage
aux/emerg
Motor
Control
HVAC System Control
INPUTS
24 VAC
Constant Fan
Compressor Call
Rev Valve
Heat Call
Capacity Select
Delay selects
Trim/Adjust
Humidistat
Available Outputs
RPM
OverSpeed
UnderSpeed
CFM Demand
Variable Speed vs. Constant Volume
• Variable speed
motor will change
or vary RPM.
• Constant volume
will change or
vary motor RPM
to deliver a preset
or programmed
CFM.
What is the difference?
Airflow Control Tips
For GE ECMTM
• Low static, high quality ducted applications will
run slowly, quietly and efficiently…..
while delivering the correct airflow.
• High static applications will run fast, be noisy
and power hungry…. The ECM may still provide
the correct airflow, but at a price!
Use good duct design practices and hold static
pressure to less than .8”, ideally less than .5”
Rotor Position Sensing
• At any given time while the motor is running, two of the three phases are energized
• The movement of the magnetized rotor past the third phase induces a voltage,
or back EMF, in this unenergized phase
• The voltage in the third phase communicates the rotor’s position to the control
• Motor Torque is regulated at a given
Phase 1
level by an accurate control of the
current in motor phases.
• The microcomputer control keeps
torque constant regardless of
operating speed.
How Does the ECM Sense
Static Pressure?
Input Power vs. RPM
550
500
Input Power (watts)
450
400
P = kN^3
350
1/2 N = 1/8 P
300
1/8 X 280W = 35W
1000 RPM
280 Watts
250
200
500 RPM
35 Watts
150
100
50
0
250
300
350
400
450
500
550
600
650
700
750
RPM
800
850
900
950 1000 1050 1100 1150
ECM Advantages
 Efficiency gain
System Pressure (Pr)
0.8
PSC
ECM
0.6
0.4
408W
745W
0.2
0.0
0
1
2
3
4
5
6
7
CFM/ Watt
Lower static pressure yields greater efficiency gain
ECM Advantages
 Static-independent Airflow
Set the airflow and go!
0.8
PRESSURE
0.7
System airflow is starved
0.6• insufficient cooling/heating
• liquid refrigerant return
0.5 to condenser
Over blowing the system
• poor moisture removal
• high power consumption
• moisture in the duct work
0.4
Typical profile with a PSC motor
0.3
0.2
408W ®
745W ®
0.1
0
1300
1400
1500
1600
1700
1800
Airflow (CFM)
1900
2000
2100
2200
2300
2400
Troubleshooting ECM Motors
The # 1 failure of ECM
motors…………… No Fault Found !
(80%)
The # 2 failure of ECM Motors
…………… Moisture. (16%)
All other failures (4%).
Power Connectors
• Connectors are keyed
• Don’t force in the wrong orientation
• Pull on the plug, NOT the cable
• DO NOT pull power cable out during
operation – Arching could occur
Low Voltage
High Voltage
16 PIN
CONNECTOR
5 PIN
CONNECTOR
Power Connectors Continued
5 Pin Power Connector
• 120 VAC uses a jumper (red wire)
• Control operates at 240 VAC
• Jumper enables voltage doubler
• Do not apply 240 VAC with jumper installed as motor and
control will fail.
• 240 VAC input does not use a JUMPER
16 Pin Signal Connector
• Pulse Width Modulation (PWM) or
• 24 VAC Thermostat Mode or
• Digital Serial Interface (DSI)
Operating Voltages Application Note
How Does the ECM Work?
 The End Bell defines
motor characteristics.
Motor Connector
Motor Section
 Only 3 motor sections
½, ¾, or 1 hp.
 The motor is really a
three phase motor
with a permanent
magnet rotor.
End Bell Assembly
Troubleshooting ECM Motors
There are some ECM
motor testers on the
market today.
Troubleshooting ECM Motors
What is Normal?
It is normal for the blower to rock
back and forth at start up.
It is normal for the shaft to feel rough
or bumpy when turned.
Don’t judge the motor by the RPM or
ramp up sequence.
Troubleshooting ECM Motors
Don’t judge the motor by the RPM or
ramp up sequence.
off
All slew rates are controlled
Profile A
Profile B
Profile C
on
Pre-run
Short
run
Full
capacity
Time: 0 - 15 min, 16 steps
Level: 6 - 100% 16 steps
Off
Delay
Troubleshooting ECM Motors
• Always make sure the motor is
oriented such that the
connectors are on the bottom
• Make sure the electrical
connections form a drip loop to
prevent any moisture from
running down the harness and
into the end bell assembly.
• A blower wheel loose on the
motor shaft can cause the
blower to vibrate, excessive
noise, and may cause motor
malfunction.
Drip Loop
Electrical Connections on Bottom
Troubleshooting ECM Motors
How do we troubleshoot ECM motors?
 Rule # 1 – If the motor is running at all. The
problem is not in the motor.
 Rule # 2 – If the motor is running at the wrong
RPM/CFM, the most likely cause is the installation
or controls sending signals to the ECM motor.
 Rule # 3 – What is the most common failure
mode? Water. Look for signs of moisture damage
and correct before replacing end bell.
Troubleshooting ECM Motors
 Rule # 4 - ECM motors, like any motor
must have a power supply. Check the
incoming power supply.
Inductor
5
4
3
2
1
AC Line
AC Line
I
}V
Gnd
} Pin 1 & 2 must be connected together for 120Vac input applications
Power Connector
(viewed from plug end)
Inductor is used on ¾ & 1 hp – 120 VAC applications only.
Troubleshooting ECM Motors
 # 5 Check inductor coil
TSTAT Connections
Pin number
9
10
111
21
31
41
51
6
Control
(male)
1
2
3
4
5
6
7
8
Connector
(female)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Common C1
W/W1
Common C2
Delay tap select
Cool tap Select
Y1
Adjust tap select
Output Return valve (heat pump only)
Humidistat (BK)
Heat tap select
24 VAC (R)
2nd stage heat (EM/W2)
2nd stage cool (Y/Y2)
Fan (G)
Output +
Troubleshooting ECM Motors
 Rule # 5 - ECM motors,
like any motor must
have a signal or switch
to turn it on, or tell it to
run.
 Controls should be
checked with a true
RMS meter or analog
meter.
 Controls will activate at
½ nominal voltage and
12 milliamps.
Out
Adjust +/-
8
7
16
15
Out +
G(fan)
Y1
Cool
6
5
14
13
Y /Y2
EM Ht/W2
Delay
Common 2
W /W1
4
3
2
12
11
10
24VAC (R)
Common 1
1
9
Control Connector Cable Half
(viewed from connector end)
Heat
BK/PWM (Speed)
(Rev Valve)
Troubleshooting ECM Motors
 Check power to control.
Pins 1 to 12 and 3 to 12.
You must have 24 VAC.
 Set thermostat to
demand for cooling.
Check for 24 VAC at
pins 1 to 6 and 3 to 6.
 If you don’t record
voltage as noted, repeat
test at control or
interface board.
Out
Adjust +/-
8
7
16
15
Out +
G(fan)
Y1
Cool
6
5
14
13
Y /Y2
EM Ht/W2
Delay
Common 2
W /W1
4
3
2
12
11
10
24VAC (R)
Common 1
1
9
Control Connector Cable Half
(viewed from connector end)
Heat
BK/PWM (Speed)
(Rev Valve)
Troubleshooting ECM Motors
 If control is defective,
remove end bell and
inspect for moisture
before replacing control
board.
 Do not apply power to
pins 8 or 16.
 Do not apply line
voltage to control
connections.
Out
Adjust +/-
8
7
16
15
Out +
G(fan)
Y1
Cool
6
5
14
13
Y /Y2
EM Ht/W2
Delay
Common 2
W /W1
4
3
2
12
11
10
24VAC (R)
Common 1
1
9
Control Connector Cable Half
(viewed from connector end)
Heat
BK/PWM (Speed)
(Rev Valve)
Troubleshooting ECM Motors
Should see 24
volts here
Out
Adjust +/-
8
7
16
15
Out +
G(fan)
Y1
Cool
6
5
14
13
Y /Y2
EM Ht/W2
Delay
Common 2
W /W1
4
3
2
12
11
10
24VAC (R)
Common 1
1
9
Control Connector Cable Half
(viewed from connector end)
Heat
BK/PWM (Speed)
(Rev Valve)
Troubleshooting ECM Motors
Energize Fan Only
Switch
Should see 12
volts here
Out
Adjust +/-
8
7
16
15
Out +
G(fan)
Y1
Cool
6
5
14
13
Y /Y2
EM Ht/W2
Delay
Common 2
W /W1
4
3
2
12
11
10
24VAC (R)
Common 1
1
9
Control Connector Cable Half
(viewed from connector end)
Heat
BK/PWM (Speed)
(Rev Valve)
any questions?
thank you!