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More 1.5kW Induction
Speed Controller Revis
The revised Induction Motor Speed Controller design presented in the
December 2012 issue was clearly an improvement over the original
circuit and PCB presented in the April & May 2012 issues. It has since
been built by quite a few readers and its operation on 3-phase motors
is much improved. However, a few readers built the modified design or
performed the mods on the original PCB and still managed to blow it up
on their particular pump or motor.
Note: the changes described in this article have already been applied to the online versions of the
two original articles on the Induction Motor Speed Controller, in the April 2012 and May 2012 issues.
W
e asked the designer, Andrew Levido, to help us
come up with some changes
to further protect the unit against
damage and to fix a few small bugs in
operation. The changes he has come
up with can be accommodated on the
revised PCB presented in the December
2012 issue.
The main problem that constructors have run into appears to be that
the overload protection was too slow
to prevent damage when running in
single-phase mode with heavy loads
and high heatsink temperatures. We
have taken a two-pronged approach to
solving this problem which involves
a faster switch-off of the IGBT bridge
if the current level rises beyond its
normal operating limits and we have
incorporated better cooling as well.
To speed up the switch-off under
fault conditions, the shunt RC filter
components involved with monitoring
the load current have been changed to
100Ω and 10nF (originally 2.2kΩ and
1.5nF). This reduces the short circuit
trip time from around 3.3µs to 1µs,
providing much better protection for
the IGBT bridge. This will also result
in a faster switch-off under excessive
load conditions, which we believe will
make the unit more rugged and also
lowers the filter impedance to improve
noise immunity.
In addition, we have reduced the
82 Silicon Chip
over-temperature trip threshold from
95° to 85°. This gives a little more
headroom to the over-current protection since if the IGBT junctions are
already at about 100°, the withstand
time at peak current will be reduced.
This change has been done in the
software; the thermistor itself is unchanged.
Also, a special condition has been
added to the software so that if the
heatsink temperature is over 60° when
power is applied, the unit will wait for
it to cool down first before applying
power to the motor.
This is to provide extra protection
as the highest currents are normally
drawn at start-up, especially when
starting under load (eg, with a pool
pump) and a hotter heatsink means
less margin for the IGBTs under highcurrent conditions.
Normally this should not be a problem since the heatsink will usually
have time to cool between motor runs
in this type of situation and besides, we
are also improving the cooling which
should result in a reduced operating
temperature.
Note that we have also changed the
value of the 1kΩ resistor feeding zener
diode ZD1 to 470Ω. This is not strictly
necessary but operates ZD1 closer to its
rated power. With the previous value
resistor, in a small percentage of cases
the reference voltage was lower than
expected. It isn’t critical but you might
as well replace this resistor when you
change the other components.
Fan cooling
A number of readers reported a
failure of the controller while starting
a motor when it was already quite hot.
Hence, we decided to add fan cooling.
This has been provided by fitting a
small fan (Jaycar YX2505) and grille
(Jaycar YX2550) in the bottom of the
box and by drilling a row of 6.5mm
holes along the top edge of the box to
provide airflow. The fan is mounted on
the inside of the box and blows the air
through and across the heatsink fins.
This has effectively negated the advantage of the sealed IP65 plastic case
but we regard the need for cooling as
paramount.
The fan is wired to the unregulated
input to REG1 (about 6-7V) and so will
run quite slowly (and hence, quietly).
While it could also be wired across the
15V HOT rail for more efficient cooling,
we are not satisfied that the insulation
of the fan is adequate.
Adding the fan meant we had to
move the output mains connector to
the right hand side of the case.
We decided to replace the flush
250VAC socket with a surface-mount
type which is more sturdy; the type we
used originally is only held in with a
single screw and they can come apart if
siliconchip.com.au
Motor
sions
by
Nicholas
Vinen
Externally, the differences are the addition
of a small fan, necessitating the moving of the mains
output socket (which is changed to a more robust type).
you are rough in inserting and removing the 3-pin mains plug.
Hence, we are taking the opportunity
to replace it with a better one. If you
are using the unit with a three-phase
motor then you can use the same connection arrangement as before but you
may need to move it across to make
room for the fan.
Users may also consider a 240VAC
120mm fan if they will operate for
long periods at full load in high ambient temperatures – if nothing else, it
will increase the lifetime of the large
electrolytic capacitors. However, a
large fan will also require a larger case.
A further change to the software has
corrected a bug in the 3-phase reversing logic. Now if the reverse switch is
changed while the motor is spinning, it
will ramp down to zero, change direction and ramp back up again.
Some users also asked for a variation on pool pump mode, where the
motor spends less time at full power
before dropping to the set speed (half
a second rather than 30s). This feature can be useful for lathes or other
equipment which start off-load and
is activated with Pool Pump enabled
and a shorting block across pins 3 & 4
of the ICSP header.
In this case, the ICSP header must
be soldered to the PCB, not just held
in by friction. We have also expanded
the available ramp time range to 1-33
seconds, allowing faster ramp rates
than were possible before.
Making the changes
If you are building the Induction
Motor Speed Controller from scratch,
you can simply fit 100Ω and 10nF
RC filter components rather than the
previously specified 2.2kΩ and 1.5nF.
If you have already built the unit,
you can either remove the PCB from
the heatsink and change both of these
components or alternatively, clip the
2.2kΩ resistor off (leaving as much
lead as possible) and
solder a 680Ω resistor
across those leads, to give a similar
time constant. However, this will not
give anywhere near as much noise immunity and may lead to false trips at
start-up, so it is better to change both
components.
If you do solder this resistor to the
top of the board, make sure it’s wellanchored as the last thing you want
is for this critical component to come
loose and possibly cause a shortcircuit in the high-voltage section of
the unit.
Now is also a good time to change
the resistor feeding the zener diode to
a value of 470Ω.
Sleeve the fan leads with a continu-
There’s also a row of holes drilled
across the rear of the case to allow
airflow from that fan on the front.
siliconchip.com.au
August 2013 83
EARTH
4004
4004
4004
470mF
1.5kW Induction Motor Speed Controller
4.7k 5W
+
47nF X2
10105122
4.7k 5W
+
+
+
4004
D9
+
180W
+
16k
siliconchip.com.au
+
+
+
4004
470m
10W
4.7k 5W
OPTO2
HCPL2531
470mF 400V
(UNDER)
100nF
OPTO3
HCPL2531
620k
THESE
COMPONENTS
8.2k
CHANGED
8.2k
D5
100nF 10
VR1
10k 1
47k
8.2k
1.5k
OPTO1
4N35
620k
10mF
ZD1
100nF
ARRIER
10mF
10mF
100nF
10mF
8.2k
4.7k 5W
100W
10nF
1
100nF
5.1V
470mF 400V
(UNDER)
CHANGED
CHANGED
IN VALUE
15W
W
220nF X2
470W
T2 6V+6V 5VA
(UNDER)
ISOLATION BARRIER
4004
IC1 STGIPS20K60 (UNDER)
10k
9
4004
110W
CON7
ICSP
4004
PP
Ext
O/S
Flt
Fault N2
A
Rev
Run
A
A
100nF
470mF
470mF
10mF
S1– 4
Fig. 1: the PCB overlay shown with the revised component values with the
section of the board (Fig.2, right) showing their exact locations.
ous length of 5mm diameter heatshrink tubing. Before fitting
the fan, you must first remove the mains socket and enlarge
the hole to suit the fan, as well as drilling four 3mm holes
for the fan mounting screws (if necessary, use the grille as
a template).
The fan goes right in the middle of the panel, orientated
so that it blows air into the case; the airflow direction is
470mF 400V
(UNDER)
100W
4004
LM317T
dsPIC33FJ64MC802
470W
100W
100W
100nF
100W
100nF
100nF
REG1
D5 D6 D7 D8
100W
IC3
680W
100W
HCPL2531
100W
100nF
1.5k
OPTO2
HCPL2531
10W
100nF
100W
15V
BC337
Q1
CON6
ZD2
NYLON
CABLE TIES
GND
100W
8.2k
OPTO3
OPTO1
4N35
100nF 100nF
4.7k
47k
10mF
ZD1
4.7k
EST
100nF
CON5
100W
10mF
10mF
100nF
10mF
RUN
+
1
RAMP
SUP
SLEE PRESSIO
VE
N
100nF
VR1
VR2
10k 100nF 10k
CON4
SPEED
FE
RRIT
E
(GPO MAINS OUTLET
MOUNTED ON
OUTER SURFACE)
100nF
620k
8.2k
1.5k
ISOLATION BARRIER
4.7k 5W
100W
100nF
U
5.1V
GND
16k
620k
8.2k
8.2k
470W
470mF 400V
(UNDER)
0.015W
2W
CON2
V
10k
IC2 LM319
+3.3V
10nF
IC1 STGIPS20K60 (UNDER)
0.5W
84 Silicon Chip
470mF 400V
(UNDER)
TH1 SL32 10015
BR1 GBJ3508 (UNDER)
NE-2
NEON
W
MINI
MUFFIN
FAN
NYLON
CABLE TIES
1.1M
REV
+
FUSE1 10A
(COVERED)
150k
150k
WARNING!
DANGEROUS VOLTAGES
NYLON
CABLE TIE
47nF X2
220nF X2
Vin
T1 6V+6V 5VA
(UNDER)
D1 D2 D3 D4
FLT1
YF10T6
CON3
NYLON CABLE CLAMP
Neutral Earth Active
BOX FRONT
PANEL
(INSIDE VIEW)
CABLE GLAND
(REAR VIEW)
4004
This photo shows the component changes along with the revised positioning for
the mains outlet to accommodate the new fan. You can also see the row of vent
holes drilled along the rear of the case. It is absolutely vital that our layout is
followed to the letter – including keeping component lengths short – and that
your soldering, especially (but not limited!) to the IGBT, is exemplary. We’ve
found several “faults” which weren’t faults at all, due to poor soldering and dress.
indicated with arrows moulded into
the plastic housing.
When drilling the holes, make sure
the fan (when mounted internally)
will sit all the way down against the
bottom of the case; this is so that the
lid will still fit.
With the fan in place, mark out the
three hole positions for the socket to its
right. If you use a surface-mount socket
like we did, you will need to rotate
it about 45°, ie, with screw holes at
upper-left and lower right. The screw
holes are 4mm while the central hole
needs to be large enough to comfortably fit four mains-rated wires through
(about 12mm diameter) and should be
smooth, ie, no jagged edges.
siliconchip.com.au
While you’re making holes in the
box, drill a row of 6.5mm holes along
the top edge, near the heatsink, to allow fresh air to be blown out of the box
by the pressure differential generated
when the fan is running.
The more holes you drill, the better the airflow will be (to a point) but
there’s a limit to how many you can
put in before the case starts looking
like Swiss cheese!
We would recommend drilling at
least as many holes as you can see in
our photos and try to keep them in a
neat row.
Fitting the new parts
Having done that, route the fan
power cable around the right-hand
side of the board and solder the leads
to the cathode of D6 (red) and anode
of D7 (blue or black) – see the wiring
diagram.
Use the hole for the thermistor wires
and the lower-right corner mounting
post as cable tie points to clamp the fan
cable. This is important as otherwise,
the solder joints could break and the
wire could easily float around inside
the case and cause havoc.
Before mounting the new mains
socket, the earth wire of the input lead
must be long enough to reach it. To
lengthen it, undo the P-clamp holding
the input cable in place, disconnect the
Active and Neutral leads, loosen the
August 2013 85
FLT1 EMI FILTER
FUSE1
ACTIVE
+325V (NOMINAL)
TH1
SL32 10015
BR1
4.7k
5W
θ
10A
~
EARTH
~
NEUTRAL
470 µF
400V
470 µF
400V
470 µF
400V
K
T1
A
A
K
6V + 6V 5VA
100nF
100nF
K
D1
D4
T2
D6
A
A
+
K
A
+3.3V
OPTO1
4N35
470Ω
OUT
IN
ADJ
1
5
110
λ
4
470 µF
100nF
2
100nF
D8
D7
6V + 6V 5VA
_
K
A
REG1 LM317T
12V
DC
FAN
470 µF
6V
1.5k
100nF
D9
K
ADDED
(OFFBOARD)
K
D5
6V
K
A
~7V
K
10k
ZD1
5.1V
A
A
CHANGED
VALUE
470Ω
0.5W
D3
470 µF
25V
6V
NE-2
K
D2
6V
150k
4.7k
5W
–
CON3
150k
4.7k
5W
+
180
ISOLATION
BARRIER
A
ALL CIRCUITRY AND COMPONENTS IN THIS AREA ARE
ISOLATED FROM MAINS & FLOATING WITH RESPECT TO EARTH
LEDS
+3.3V
Vin
K
A
GND
1
3
C
LM317T
ESTOP
OUT
ADJ
IN
ZD1, ZD2
K
D1– D9: 1N4004
A
OUT
GND
3
HEATSINK
THERMISTOR
TH2
1
100nF
100nF
CON7
2
3
100nF
K
ZD2
15V
CON6
A
C
Q1
BC337
B
680Ω
E
K
A
λ LED1
K
SC
2012
100nF
100Ω
CON5
GND
100nF
SPEED
100Ω
2
REV
VR1
10k
1.5k
1
RUN
RAMP
θ
E
A
4.7k
4.7k
B
VR2
10k
100nF
+3.3V
CON4
BC337
OUT
100Ω
2
A
λ LED2
K
A
λ LED3
K
1.5KW INDUCTION MOTOR SPEED CONTROLLER
Fig.3: for the benefit of those who don’t have access to the original article(s), we are reproducing the circuit diagram in
full. The three changed components are identified on this circuit, along with the new 12V DC fan. All other changes are in
software which, of course, means that the IC3 will need to be re-programmed with a free download from our website.
86 Silicon Chip
siliconchip.com.au
19
620k
220nF
250VAC
X2
620k
22
47nF
250VAC
X2
25
47nF
250VAC
X2
16k
CON2
0.015Ω
24
2W
+15V HOT
W
12
IC2a
4
V
18
8.2k
11
5
U
21
3
1 0 nF
100Ω
+15V
HOT
CHANGED
VALUES
1M
23
Vcc 5
2
Vboot-U
20
17
16
ALL CIRCUITRY IN SIDE
THE PINK AREA
OPERATES AT
DANGEROUSLY HIGH
VOLTAGES – CONTACT
COULD BE LETHAL
Cin
100nF
IC2: LM319
OUT-U
IC1 STGIPS20K60
15 SD/OD
3
Lin-U
4
Hin-U
9
Lin-V
10
Hin-V
13
Lin-W
14
Hin-W
Vboot-V
OUT-V
Vboot-W
OUT-W
GND
1
7
6
12
11
10µF
25V
MMC
10µF
25V
MMC
10 µF
25V
10µF
25V
MMC
8
10
7
IC2b
8
9
6
THIS SYMBOL
INDICATES
'HOT' COMMON
+15V
HOT
OPTO3 HCPL-2531
10Ω
100nF
2
3
4
5
6
7
28
AVdd
100nF
13
100Ω
RB12
AN0
RB14
AN1
RB15
AN 2
RB13
RB1
RB11
RB2
23
100Ω
10
100Ω
11
100Ω
12
RA2
RB10
RB9
RB4
RB8
RB7
RA4
MCLR
PGED
AVss
27
siliconchip.com.au
Vss
8
Vss
19
PGEC
8
λ
7
8.2k
λ
8.2k
8.2k
6
5
26
24
22
OPTO2 HCPL-2531
100Ω
10 µF
6.3V
MMC
RA3
4
3
25
20
C1IN+
1
2
Vdd
IC3
dsPIC33FJ64MC802
9
100Ω
+3.3V
21
17
18
16
1
14
15
1
2
100Ω
4
3
POOL
8
λ
7
λ
6
+3.3V
5
EXT
O/S
FLT
47k
ICSP
SOCKET
1
2
3
4
5
JUMPER FOR
SHORT BOOST
MODE
NB: PARTS ARROWED
CHANGED FROM VALUES
SHOWN IN ORIGINAL
CIRCUIT OF APRIL 2012
August 2013 87
cable gland nut and pull the cable out.
You’ll have to guesstimate how
much of the insulation to strip off it
but perhaps another 150mm will be
enough – remember that the earth
wire will have to go over the fan and
then some way into the back of the
mains socket.
Feed the cable back in through
the gland but leave it loose. Ignore
the extra-long Active and Neutral
wires for now and feed the earth wire
through the socket access hole. Twist
its exposed copper together with the
new, longer earth lead for the PCB and
screw them tightly into the terminal
in the rear of the socket.
Similarly, connect up the new active
and neutral wires too and feed them
back into the case.
All the socket terminals should be
done up extra-tight with a flat-bladed
screwdriver to ensure the wires can’t
come loose.
With the four wires in place, mount
the socket using M4 machine screws
and nuts, with a shakeproof washer
under each head and nut. Make sure
they too are done up tight.
You can then cut the new motor connection wires to appropriate lengths
and connect them to two of the motor
output terminals; don’t forget to slip
the ferrite suppression sleeve back
over them before making this connection and use a cable tie to prevent it
from moving around too much.
The earth wire with the loose end
is run to the earth point on the input
screw terminal barrier at the left side
of the PCB and this can be tied to the
88 Silicon Chip
Additional
parts required
1 60mm 12V DC fan (Jaycar YX2505)
1 60mm fan grille (Jaycar YX2550)
1 surface-mounting single mains (3pin) socket
1 100Ω 0.25W resistor
1 470Ω 0.5W resistor
1 10nF MKT metallised polyester
capacitor
1 300mm length 6-8mm diameter
heatshrink tubing
4 M3 x 20mm machine screws and
nuts
4 M3 shakeproof washers
2 M4 x 20mm machine screws and
nuts
4 M4 shakeproof washers
1 250mm length mains-rated earth
wire (yellow/green striped), 10A+
1 200mm length mains-rated neutral
wire (blue)
1 200mm length mains-rated active
wire (brown)
10 small cable ties
other wires connecting to the PCB
(see photos).
It’s then just a matter of re-clamping
the mains cable, doing the gland nut
up and trimming the incoming active
and neutral wires to length before
re-connecting them to the respective
power input terminals.
Make sure all the wiring is properly
tied down so that even if one of the
wires breaks or becomes disconnected
from the PCB, it can’t make contact
with something that it shouldn’t – if
in doubt, refer to the photos of our
prototype.
Updating the software
To take advantage of the improved
protection features, bug fixes and extended ramp setting range, you will
need to re-program the microcontroller.
Make sure the unit is completely unplugged from mains before doing this.
It’s simply a matter of connecting the
programmer (eg PICkit3) to the 5-pin
in-circuit serial programming header,
enabling the PICkit’s 3.3V power supply for the micro, loading the HEX file
and re-flashing the chip.
Alternatively, you can swap the
dsPIC33 chip out for another one
which has been pre-programmed
with the latest version of the firmware
(1010512B.HEX).
This will be made available for
download from the SILICON CHIP website, free of charge.
Once the chip has been reprogrammed, go over the unit carefully to
make sure all the changes have been
made properly and nothing is loose,
especially the mains wiring. You can
then go through the test and set-up
procedure from the previous article
(May 2012).
Essentially, this involves powering
the unit up from mains with no load
attached and checking that the neon
lights up and the green LED flashes and
then after a short period, goes solid.
Assuming it checks out, you can
switch off, connect a motor (ideally,
unloaded) and power it back up to
check that it is operating normally. SC
siliconchip.com.au
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