Turquoise 3-Phase Brushless DC
Craig Carmichael, January 2012
IR2133 triple high voltage MOS gate driver chip,
4070 quad XOR gate chip &
12 IRFP3206 MOSFETS (60 volts, 120 amps)
3. Current Ramp Modulation
4. Controller Operation
5. Assembly: Layout and Power Circuit Considerations
6. Cable Convention; Tec Tips
8. Bits and Pieces
DISCLAIMER: Anything you do with this information is done on your own
responsibility. I make no waranty of correctness, suitablility or
applicability of any of it.
This device is a solid state 3-phase brushless DC motor
controller incorporated into a small wiring chassis, created for the Electric
Hubcap 5 KW pancake motor. As implemented
it should work for motors up to about 6 KW, 18 to 42 volts
battery supply (nominal), under about 130 amps, but it's only been
tested with the electric hubcap at up to 42 volts and at under 100 or
Other motor ratings or
voltages will require different choices of power components, different
resistor values, etc, though the controller can be used as-is down to
about 14 volts (12 V sometimes works if the battery is well charged) if
the amps are also within limits. (It can be used at
12 volts nominal if the 12 volt regulator is bypassed. Below 10 or 11
volts supply it will crap out.)
A zenor diode/power transistor voltage regulator circuit
drops the motor battery voltage to 12-15 volts to power the controller
circuits - the two integrated circuit chips, passive components, and
the power MOSFET gates. A 7805 five volt regulator supplies voltage for
the 5V max. logic
inputs of the IR2133.
Certain aspects of the construction are considered
The integrated circuit 'chips' and associated components
are mounted on a small
printed circuit board. The power MOSFETs (along with a dozen filter
capacitors) are mounted spread out on a heat sink in two rows and
are wired to the circuit board with short lengths of hook-up wire.
(Same as previous controllers.) The
board is mounted as close as possible to the MOSFETs, consistent with
spreading the mosfets out for good heat dissipation. (Note: The shorter
the wires are the better. Especially the gate drive lines must be as
short as possible and must be twisted pairs with their respective Vs or
Com. The layout is designed to minimize the length of the power wires.)
Two cables of small wires connect to two .1" header pin
strips on the circuit board. A 6-pin one goes to the motor for magnet
position and temperature sensors, a 10-pin
one (may become 11) goes to
the operator controls and readouts.
The controller is mounted as one side wall of an aluminum
chassis. Cooling is passive. Heatsink fins made of aluminum roofing
flashing are clamped to the outside of the chassis opposite the power
transistors inside, eliminating the need for custom heatsink
extrusions. The entire chassis also acts as a heatsink.
The side wall with the motor controller can be removed
from the chassis for
servicing or replacement without dismounting the rest of the chassis,
allowing the chassis to be used as the wiring junction box for the
system. Box dimensions are kept minimal to accommodate the often
limited available mounting space.
An open controller (V1 PCB) showing the controller base with heatsink
bars and aluminum roofing flashing fins
(This one has a specially cut-down chassis to fit a motorcycle -
normally the back side here mounts on a wall.)
3. CURRENT RAMP MODULATION (CRM)
CRM is my own term for variable frequency modulation
based on varying the current supplied to the motor rather than the
voltage as in pulse width modulation (PWM). CRM provides maximum
torque at stopped and slow RPMs, while the switching speed and losses -
and hence the heat in the controller - are greatly reduced at higher
speeds with high loads. CRM is analogous to direct torque control,
since torque is directly proportional to current.
With the motor stopped or greatly underspeed, when a coil
is turned on, the current ramps up very quickly as there's little or no
back EMF and the full DC supply voltage is effectively applied to the
coil. With PWM,
either the switching speed must be set very high (eg, 10-50 KHz) to
motor currents, or the current limiting will trip the motor off early
PWM cycle. Since PWM cycles are fixed periods, this means the motor is
"off" most of the cycle, which greatly limits low-speed torque. Low
speed is usually the worst time for low torque in a transportation
On the other hand, once the motor is turning at speed, the
high speed, high power switching makes considerable heat in the
controller, and there's no need for high speed switching at higher
With CRM, the current ramps up to the maximum value (set
by the control potentiometer)
whenever it does, and the cycle is immediately terminated with a short
fixed off period, eg 10 to 50 microseconds (as in, below 100 kilohertz
to below 20 kilohertz). The next cycle starts immediately after that.
At low RPM with fast current ramp-ups, the modulation is thus at a high
frequency. As the motor speed increases, the motor's back EMF lengthens
the time it takes for the current to rise to the assigned level, so the
"on" time lengthens and the modulation frequency drops. The frequency
is whatever it needs to be to provide the torque the control
is set at - at any speed.
In broader terminology, CRM is
an inverse form of pulse
frequency modulation (PFM), where a pulse of a fixed period is repeated
at a variable frequency. In CRM, the "off" pulse is the fixed period,
and the variable "on" period modulates the frequency.
A drawback to CRM in
some applications is that it's hard
to set a constant speed without feedback, except with a constant load
where speed varies with torque. For vehicle transportation, the
"electron pedal" operates quite like the familiar gas pedal, and
drivers should have
no trouble using it.
4. CONTROLLER OPERATION
International Rectifier probably doesn't realize that
their IR2133 triple MOS gate driver chip can be used as a single chip
three-phase brushless motor controller with advanced 'current ramp
modulation' control. At least, they are too modest to mention the fact,
and they haven't taken a couple of simple steps needed to provide for
both forward and reverse motor rotation, hence necessitating the second
In explaining the unusual aspects of how the controller
works, first, let's look
at the chip and its pins:
|(ITRIP) I-Trip .1
|28. Fault (FAULT)
|27. LowIn3 (LIN3)
|(CAO) CurrentAmpOut .3
|26. LowIn2 (LIN2)
|(CA-) CurrentAmpMinus .4
|25. LowIn1 (LIN1)
|(CA+) CurrentAmpPlus .5
|24. HiIn3 (HIN3)
|(SD) ShutDown .6
|23. HiIn2 (HIN2)
|(VSS) Ground .7
|22. HiIn1 (HIN1)
|(COM) Common .8
|21. Vcc (VCC)
|(LO3) LowGate3 .9
|20. VBias1 (VB1)
|(LO2) LowGate2 .10
|19. HiGate1 (HO1)
| (LO1) LowGate1 .11
|18. MotorPhase1 (VS1)
|(VS3) MotorPhase3 .12
|17. VBias2 (VB2)
|(HO3) HiGate3 .13
|16. HiGate2 (HO2)
|(VB3) VBias3 .14
|15. MotorPhase2 (VS2)
Note: for convenience and to avoid varying system
interpretations, I'm going to use underline
instead of overline for active low signals.
Pins 9 to 20 are the three half-bridge, 12 volt, high
power N-channel MOSFET drivers, with the three floating high gate drive
referenced to the output voltage of the motor coils. This
critical area is where International Recifier's chips singularly excel,
and since blowing up MOSFETs and whole controllers from power handling
glitches is the usual problem with motor controllers, it's the reason
for choosing IR chips in spite of any logic peculiarities.
Pins 22 to 27 are the six inputs corresponding to each of
the six driver gate outputs. (They are inverted from the outputs, which
is of little
consequence except for reversing the already arbitrary sense of the
forward-reverse switch.) The fact that there are six inputs instead of
three seems to show IR's weakness in conceiving their logic designs:
there are six
outputs, but the HIGH and LOW side of each pair can't both be ON at
creating a short circuit from B+ (motor power) to common through the
logic already prevents such shorts for bad combinations of
inputs, so the extra three inputs appear to have little real value - at
least for our application. The three pins could provide more useful
As it is, the three signals from the magnet sensors in the
motor go to both the high and low inputs, in a skewed arrangement that
tricks the IR2133's internal logic to do the common six-step
commutation that it could have done just as well with three pins:
MagnetSensor1: HiIn1 & LowIn2
MagnetSensor2: HiIn2 & LowIn3
MagnetSensor3: HiIn3 & LowIn1
Ground (Vss) and Vcc need little explanation. "Common"
(COM) is the
'ground' connection through the current sensing resistor to the low
side of the
power MOSFET bridges feeding the motor coils. Since, in a high powered
motor, the current sense resistor is just a straight length of thinner
wire or other shunt, Common is "almost ground". (straight wire - NOT
coiled into an
I'm presently using nickel-brass ("nickel-silver") wire - it doesn't
conduct as well, so it's shorter for the same resistance. It's
also heating up. I'm presently
trying out 2mΩ, making 2 mV/A or 260mV for the max 130 A. (BTW I had
the solder at the bus end of this 'resistor' break loose on one
controller, and (like most faults), most everything fried. 100% good
connections are vital in a solid state, high power circuit. Hence the
wire now has a clamp at both ends.)
The "current amp" on pins 5, 4, and 3 is simply an op-amp,
intended to drive an external current indication signal. We have a
better use for it as a voltage comparitor, eliminating an external
Pin 6, "SD" or "ShutDown" is intended to be an input for
externally detected "fault" conditions, that shuts the power drivers
off to the
motor. Our "external fault" is that the motor run switch is in the
All the "fault" conditions internal and external are
prevent the output from turning the mosfets on again until pin 2, "FaultClear"
is asserted. Pin 1, "I-Trip", is an input that causes a "fault" if it
goes above 0.5 volts. It is intended that this be connected as an
analog signal (directly
or indirectly) to "Common" to sense "too much" current going through
the sense resistor. Pin 28, Fault, is an open drain output that
indicates the outputs have been turned off and the motor is unpowered -
for any reason.
In this controller, the current amp "+" input is connected
to "common" to
the motor current. Nominally, the sense resistor is .002 Ω (), so the
across it is 2 mV / Amp. The "-" input is connected to the control
potentiometer ("gas pedal" or ???) that indicates how much current the
motor is supposed to receive, from 0 to (nominally) 254 mV for 0 to 127
amps. The op-amp output goes to I-Trip - as an
"on-off" signal rather than an analog level - to turn the motor coils
off when the current has ramped up to the desired point. (We could as
easily swap "I-Trip" and "SD": either one going high turns the motor
off. But we won't.)
The Fault output is connected via a 15 microsecond
R-C delay circuit to FaultClear, providing the "short fixed off
period" that ends a current ramp modulation cycle. After the 15 uS
the motor is turned back on - unless the potentiometer is entirely off
for zero amps, in which case I-Trip will stay high and hold Fault
on even as it asserts FaultClear. The op-amp's reading of
"common" is slightly biased up (15 millivolts, via a 100 ohms, 100 K
ohms resistance divider to the +15 volt supply) so the potentiometer
can definitely hold its input slightly lower than the current sense at
the zero end.
Let's "rename" these pins in
accordance with these usages:
"ShutDown" becomes the "OFF/ON" switch. A pullup
resistor ensures that the motor stays OFF if the control cable is
"CA-" becomes "ControlVoltage".
"CA+ becomes "CurrentSenseVoltage"
"CAOut" becomes "CurrentSwitch"
"Fault" becomes "OffTime": the output has
turned off for the rest of the modulation cycle: this is asserted
the "short fixed off period".
"FaultClear" becomes "StartCycle" to initiate the next
Since OffTime connects to StartCycle, the
'short fixed off period' ending the current ramp modulation cycle is
set by an R-C time delay between them.
There's a reason "Fault"
can be triggered besides "I-Trip" and "SD": if the voltage driving the
mosfet gates drops below about 9 volts (which would result in most
mosfets partly conducting and dissipating much more power than they
can handle), the "undervoltage detect" will shut it off. For
transportation propulsion, shutting it down while (eg) a car or
airplane is in motion is usually the most dangerous option, so the best
way to handle it is to end the cycle and try again -- exactly what
we're doing anyway. Also, undervoltage is unlikely to happen since the
36 to 42 volt battery supply has to drop to about 14-16 volts before
the regulated 12-15 volt supply voltage would drop. The 2uF ceramic
on the high side charge pumps should keep them going for quite a while
- there should certainly be no problem in normal operation.
Note: Smaller capacitors and low motor voltages, eg 12-18
volts, may cause hickups as the motor starts. Once it's spinning much
smaller values would be fine. This will vary by motor and voltage. IR
recommends nothing less than .47uF.
Forward/reverse is the one vital function that
can't be implimented on the
IR2133 chip. This is especially where it would
have been nice to have just three input pins - to have a pin left over
this function. Reverse is implimented simply by inverting the three
sensor signals. That way, "north" and "south" magnets appear to be
reversed, and the coils turn on the other way. The
simplest way to invert a signal or not depending on switch position is
an exclusive or gate. The three magnet sense signals are optionally
inverted by one
fwd/rev switch (per the circuit schematic),
so a quad XOR gate is the choice.
Since we're operating
at 12-15 volts, a 4070 15 volt CMOS logic XOR gate would seem to be
the simple choice, but frustratingly the logic inputs on the IR2133
work only up to 5 volts. So we have to add a 5 volt regulator and use a
74xx86. (74LS86, 74HC86, etc.) That's the second chip. (I used a SOIC
to fit it on easier.)
NOTE: The first version uses a 4070 at 15 volts,
modified with diodes to make the outputs "open drain". It works fine,
seems reliable. There was a hickup in getting PCBs for the second
version and it hasn't actually been made and tested yet. (2012/01/20).
Schematic (version 2):
PC Board (V2):
Eagle circuit board layout program files:
The solder pads on the PCB for the phase A mosfets now go:
A hi gate ---\ twisted pair
A out ----/
A low gate --\ twisted pair
and the same for phases B and C. B+ and Ground are separate solder pads.
MOSFET/Heatsink component wiring
Notes: 1. I now only use one [set of] AGC/AGO fuses on the power line
(now that things are more reliable)
2. A, B and C out now have a separate balancing wire from each pair of
MOSFETs to the terminal block.
5. Assembly: Layout and Power Circuit
There are some considerations peculiar to high power
circuits. I learned many of them the hard way, finally finding there
are explanations for 'inexplicable' failures, and I'm explaining them
here so you'll see there was logic behind the way things were done.
That way you won't arbitrarily, eg, use thicker wire in a heavy current
the thin wire specified was used for a reason (as would be my own
inclination). In particular, in order
stray inductances, most of the signals need
to be kept short and straight. Minimizing stray inductances minimizes
spikes and glitches in the signals, which become extreme at high powers
driving an inductive load such as a motor.
* The DC power should be well filtered right at the mosfet
half-bridges. This controller uses 12 mosfets instead of 6 in three
legs: each mosfet is paralleled, doubled up, to handle the high powers
and currents, which switch on and off suddenly, creating considerable
spikes. Across each bridge is a
270uF, 100 volt capacitor with as low a series resistance as I could
conveniently find: six capacitors, 1620 uF total. I have no close idea
what's optimum, but when I used three 100uF/64V capacitors early
on (a value given in an app notes example circuit), they actually blew
up quite soon -- across a 36 volt DC line coming straight from
1200uF might be
* The 3-wire external power cable from the controller to the motor
should be no more than 3 feet long. This means the controller should be
mounted quite close to the motor. If the motor is on a car wheel, the
controller should be just inside the car next to the same wheel.
* Varistors between the motor phases are used to help dampen the worst
spikes coming back from the motor. Present choice is 36V80Z. These
were chosen for 36 volts and might gradually start popping at 42 volts,
would necessitate going to the next voltage up. It would be best to
several in parallel as the mosfets are only rated for 60 volts.
(For 42 volts consider going up from IRFP3206s to 70
volt rated IRFP3207s.)
* If the gate wires (between the driver chip and the mosfet gates) "are
about 2 inches long they should be run with twisted pair wires."
(International Rectifier: AN-947. They aren't kidding - I had failures
from shoot-through currents spuriously activating MOSFETs until I
started twisting wires together.) It is suggested elsewhere that the
be as close to the mosfet gates as possible. (Allegro: STP 02-3)
However, the power
mosfets need to be well spread
out on the heatsinks for cooling. The most compact wiring arrangement
found (shortest power wires) consitent with good cooling was to place
them an inch and a half apart
in two lines: 6 low side drivers and 6 high side drivers, on two 9"
long heat sink bars. Thus it's 1.5" between gates of the doubled-up
mosfets of each position. And the IR2133 chip itself is over an inch
long, so the runs are up to almost two inches
before they even leave the small circuit board. The gate resistors are
on the PC board too, to keep the hard-wiring from getting messy. It can
seen the two inches will be considerably exceeded, and beyond the
resistors. This is particularly true of phase "C". The circuit board is
bolted onto three mosfets in common with their holding bolts. Since
there are six pairs of mosfets and
two pairs per phase, one phase especially - I made it "C" - will be
distant from the board. The board is bolted to
low-side mosfets 2 ("A"), 3 ("B"), and 4 ("B"), leaving 5 and 6 ("C")
more distant. (The "V2" board layout shortens "C" gate wires over V1.)
The gate and source sense voltage wires run as a twisted
pair from the
board to the nearest mosfets on both
low and high side.
* When using two paralleled power transistors to handle heavy loads, it
is necessary to ensure they are balanced, that is that each one takes
about 1/2 the load and dissipates about 1/2 the power. This is a bit
tricky, because once one has heated up a bit more than the other, its
internal resistance drops more, and it starts taking more of the load
and heats up even more, which continues in a positive feedback "thermal
runaway" loop. If the load is too heavy for one transistor, the one
that started heating up first will blow. (Someone says I have this
backwards, that for MOSFETs it's a negative temperature co-efficient. I
should check this out, but it's still best to balance them in case of
non-identical component specs.)
Balancing is done by using small, equal value resistances
in the power side of each paralleled circuit. If the mosfets (cold) are
.002 ohms when ON, and balancing 'resistors' of .002 ohms are used,
then even if the internal resistance of one mosfet should drop to .0005
ohms by heating, the total resistance in each leg is .004 and .0025
ohms, instead of .002 and .0005. Without the balance, the one mosfet
would take 80% of the load; with it, it takes just 61% even in this
extreme case. And because of the balancing, it probably won't get this
extreme. ("Typical" value for IRFP3206 mosfet is .0023 ohms cold.)
But what is used to obtain such tiny resistance? The
answer is: equal lengths of copper wire on each side, of a thinner
gauge than would normally be selected for the given current. These are
the wires used to connect the mosfets bridge outputs to the motor cable
connector block. Again we want to keep the wires to the motor as short
and straight as is practical, so we pick the gauge based on the
distance of the mosfets from the motor connector block. For four inch
wires, we use #18 AWG wire to obtain roughly this resistance, or #16
for 6" wires.
6a. Cable Convention
The control cable probably won't work unless it's wired
right, and the motor sensor cable is wired straight through, so there's
no need to dwell on them.
The 3-phase power cable to the motor could be wired
arbitrarily, and the motor side depends on the relation between the
coils and the magnet board in the motor, which is likely to be pretty
much random by
the time three wires are wired to nine coils and are sticking
out of the motor. There are six ways to connect the two 3-wire plugs,
and only one of them is right. Essentially, pins are swapped until the
motor runs properly in both directions. (There are two ways that it'll
seem to run okay in one direction but poorly in the other, drawing a
lot of current with no load.)
If both the motor and the controller were wired
arbitrarily, the motor would only run right on one controller out of
six. However, if the controller end is standardized, then once the
motor is running on one controller, it will run on any one. So I have
defined a convention for wire colors and the controller side of the APP
Inside the controller, the three phases I arbitrarily call
"A", "B" and "C", go from left to right, looking from the front
side of the circuit board where the header sockets are.
The wire colors, whatever they are, (resistor color code
values) are used in numeric order, so that A is the lowest numbered
wire and C is the highest. Thus, with a cab tire cable having white,
black and green wires, Black (0) is A, green (5) is B, and white (9) is
used for C.
At the other end, looking into the open end (the end
that mates with the other plug) of the
APP plug with the plug pins on the bottom side, A, B, C go left
to right - in this case: 0, 5, 9, black, green, white.
6b. Tec Tips
At the heatsink, the B+ supply and the common return
busses are #10 solid wire above the MOSFETs. These have a bunch of
capacitors to filter the DC supply to the MOSFETs. The heavy wiring is
above the MOSFETs; the light control wiring to the PC board is
The easiest way to get at the control wiring is often to
unbolt the 12 MOSFETs from the heatsink. Then (with chassis connections
undone) the entire circuit assembly will pull free of the chassis.
However, when installing more than one or two MOSFETs,
it's best to have the heatsink bars on to line up the new ones with the
mounting holes. In this case a good way to
get better access is to unbolt the heatsink bars from the chassis,
which again allows removal of the circuit.
It is important to remember that almost any flaw, any
short or missed or bad connection anywhere, will most often result in
destruction of the circuit - usually the MOSFETs and-or the IR2133
driver chip. Be sure of every connection. Check everything, including
for shorts from each MOSFET drain to the chassis, ie, for a bad
heatsink insulator. Also be sure the bolts are tight, or the MOSFET is
likely to overheat and blow under load.
Making The Chassis/Wiring Box
last updated Oct 2010)
[January 2012 comments]
A larger chassis - motor test unit
for the shop
current visualization (after considerable experience) of the
most practical layout is an aluminum box about 6" wide, 10" tall, and
4.5" deep [shrinking to 4" x 9.5" x 4.25" - Jan 2012], with the motor
controller occupying one removable side. More
generally, the box has to have the height and depth of the motor
controller side piece, currently 4.25" x 10". The depth depends on the
circuit board size and on how closely the two rows of heat sink are
spaced. It could all be done in less space, but the power transistors
should be well spread out from each other for good cooling, to avoid
destructive thermal run-away. The width of the box is "whatever" as
long as there's room for the components and wiring. The test unit for
the shop is 7" wide, the one in the car is 6", and the one for the
outboard motor, if it is to fit under the hood of the outboard, must be
only about 2" or so - I'll be looking for a very small circuit breaker!
is intended that the box be mounted on a vertically oriented surface,
eg, the rear face screwed to a wall of the car. The box can be oriented
vertically (preferred), sideways with the heat sink fins up, or to any
diagonal position that fits well and lets rising air flow past the heat
sink fins -- or to any position if the cooling seems adequate.
In the prototypes the motor
controller was mounted in the
front cover of a shallower box. This was a poor arrangement. With the
heat sink fins attached, it was effectively quite deep anyway, the
power wires had to be longer to attach them to the open cover, and the
wires were being moved around as the cover was being closed, without
being able to ascertain they were in good positions (eg, not pushing on
circuit board components) once in place.
If, on the other hand, the motor controller had been
mounted in any
non-removable part of the box, the whole box would have to be
dismounted from the car to service it.
For that reason, the removable side idea was chosen. Even
off-the-shelf aluminum box is found, one side will have to be replaced
with a removable aluminum panel, about #12 gauge.
front and back of the box can
be flat aluminum covers that
screw on to the "frame" side pieces. The back should be about #12
gauge; the front cover can be thinner, #14 or #16 if desired.
Alternatively the back, top and bottom may be one piece (#12), bent
around, with 1/2" lips to hold the top and bottom edge of the front
On the left (or right) side panel (10" x 4.5") the motor
mounted. This whole side with the controller can be unscrewed and
removed from the rest of the box for replacement or servicing. The
aluminum "roof flashing" heat sink fins are on the outside of this
face. (Note that the screws for the back cover, and probably for the
top or bottom or both if used, must be screwed on from the inside to be
accessable once the box is mounted.)
The breaker/switch is located on the top or the other side
controller, as convenient, or an external battery post mounted switch
may be used.
The solenoid, terminal blocks and grounding post are
attached to the
back of the box.
The filter capacitors sit in the bottom of the box,
clamped in place.
Wire and cable entry holes are made where practical and convenient.
course, Turquoise Energy Ltd.
plans to offer ready-made wiring
boxes complete with controller and all parts as soon as it’s possible
to do so. (That just isn’t going to happen this month, April 2009!)
A convenient construction of the
box is with the following aluminum
sheet metal pieces:
1. a flat 6" x 10" back cover piece, #12 gauge.
2. a flat 6" x 10" front cover piece, #12 or #14 gauge.
There are a number of options for
the edges. If there is no access
to sheet metal bending equipment, the edge pieces are cut to just the
4.5" depth of the box, and six feet of ‘L’ angle of about 1/2" x 1/2"
(or 3/4" x 3/4"), by about 1/8" thickness, are purchased to attach the
sides to the front and back covers. Another 12" - 16" or so of ‘L’ can
be bought to connect the edges of the frame together at the corners.
Otherwise, the pieces are 6" (or 6.5") across and 1/2" (or
are bent along the edges forming a shallow bracket ( ‘[’ ), leaving the
4.5" remaining width for the box depth. (Note: see drawings for the
I got excited when I found extruded aluminum brackets
made for windows, 2.5" wide with 3/4" lips. Surely four short lengths
of that would frame the controller box, with flat covers on both sides
and no aluminum bending required! Then I decided the motor controller
should go in the side, requiring a deeper box, and I couldn’t find
similar but deeper 4.5-6" wide strips. (There are such shapes more or
less, but they are "structural", eg with aluminum 1/4" thick.)
4.5" or 5" ('depth', per above)
x 10" side piece of about #12
gauge to mount the motor controller on. This may be extended to 11" and
1/2" lips bent into the ends to meet (and maybe screw into) the other
The three remaining 'frame' edges
may be formed from one piece,
two or three, and may be a thinner gauge than the piece the motor
controller mounts on, eg #14, if desired:
a single 'depth' x 25" piece is
formed into a shallow bracket, '[', the folds being .75" each and the
main side area 4.5" across. The
edges are then cut at 45º angles to make 'V's at 7.5" and 17.5".
piece is bent 90º at those locations to make three sides of a
rectangular frame. For the last .5" at each end the overhangs are cut
off and the ends are bent over 90º to form .5" lips onto the
(b) Three separate pieces, 6", 6"
& 10". Again 1/2" can be added
as required for tabs to attach the frame pieces together.
The aluminum pieces for the box: Flat (a couple of pre-bent lips);
bent; fitted; motor controller side removed.
The size of the controller was at first 8" x 10". When I
the parts, it didn't seem to need that much room, and I cut it down to
6" x 10". It's looking like it could easily be smaller yet.
The motor controller (top side) in the chassis box
Box with controller side removed.
The next three diagrams show the pieces of sheet aluminum. (CAD?
What's that?) All the pieces should be about #12 gauge (~.080") except
the cover, which may be #12 or #14. If thinner pieces are used, the
screws that hold them together and hold the equipment in place may
strip and things will come loose. (I discovered this using a thinner
piece (#14 or #16) for the long side opposite the controller.) The
front cover may take bashing by luggage in the car, so it shouldn't be
too thin either.
The cover in the photos has seven holes, but four is
plenty as per the
diagrams. The side holes are really extras, and the middle hole on the
controller side puts the screw right against the circuit board and
should be omitted. Likewise, the center screw through the back cover
has the screwdriver rubbing up on the PCB and should be omitted.
Another good idea would be to make the side flaps of the
controller piece 1.5" deep like the bottom flap, with the screws at
1.25" also like the bottom. This would get the screwdriver a bit
farther from the circuit board. Note that there are no holes near the
bottom of the side flaps - it would just be too hard to get the screws
in and out.
I finally fabricated this motor controller enclosure
July 2009, after having done circuit boards in June.
Final dimensions of this enclosure are 10" x 6" x 4.5",
aluminum "roofing flashing" heat sink fins.
The 10" height allows speading the power components for
and for good heat dissipation.
The 4.5" depth is to the inside of the two covers, ie, the
heights. The motor controller won't fit if it's less. (A narrower PCB,
eg with surface mount components, would allow a slightly shallower box.)
The 6" width provided enough interior space. (Originally I
cut it 8"
wide, but it seemed to have waste space and I cut it down. Worse than
cutting the aluminum was having to re-do 2 of the 3 layout diagram
Bits and Pieces
(Last updated Oct 2010)
[a few Jan. 2012
The Wiring Box with all components & heavy cables
(Also see the wiring diagram of this at the end of the chapter)
Added later: Wire Clamps.
[I still don't think these are finished products, just better than what
Buss Bar Clamps: fat nickel-silver wire on right is the current sense
resistor to ground.
The bottom of the wire was flattened with a hammer, looped around and
drilled to form a clamp.
Powerline/Fuses Clamp & bits.
Holders for AGC/AGO automotive fuses are just sockets for spade lugs.
This box [refer to top image of the three above] goes behind the right
rear wheel of the station wagon.
* The battery leeds + (+36V, red), and - (zero V, black) enter at the
bottom left. The red goes to the bolt-in side of the breaker (black,
left), and the two breakers (it's a double 100 amps house breaker) are
tied together in parallel. A green grounding wire comes through a
separate hole on the left. The left header connector goes to the motor
sensors and the right one to the operator controls at the front of the
* The ground, battery "-" and motor controller ground wires all tie
onto the one grounding lug bolt on the back cover of the box, seen
towards the left. The three-phase power from the controller, via filter
capacitors, and to the motor, ties into the copper triple terminal
* The power from the breaker comes out the plug-in connectors (normally
these are the input when it's mounted in a breaker box) to two pieces
of thick sheet metal that fit securely, and goes to one contact of the
"solenoid" relay. (I later put in a longer #10 wire so the relay could
be bypassed for testing.)
* The motor cables (three phase power and commutator optics) enter at
the lower right through a hole behind the capacitors.
* Lower right, at the front: three 7uF spike filters (motor "run"
capacitors from a motor shop) [DITCH THESE] across the three phases
with metal oxide varistors ("MOV"s - V36ZA80 [KEEP, solder at terminal
blocks] soldered across them for
* Inside the "top" side (left or right side when mounted as convenient)
is the motor controller. "Above" the box are the aluminum "roofing
flashing" heat sink fins clamped on the outside of the cover.
The Motor End
5-pin "trailer lights" socket & plug for the motor optics, and the
Anderson "PowerPole" 75 amp connector (red) to the motor coils. The
"A.P.P." plug & socket are identical - one is simply flipped upside
down and they fit together. So far, these are the only suitable
connectors I've found. Prior to finding them, I had resorted to making
my own 'thin line' three-phase plugs and sockets! Note the holes that
allow bolting the socket onto something. I plan to fill the one on the
car with grease since they aren't intended for exposure to weather.
Main Power Switch or Circuit Beaker
There are a number of possibilities
for this switch. There
are battery switches that clip to the terminal post of an automotive
battery. One of those could be used and would be external to the wiring
box. There are also switches made for heavy battery loads that could be
mounted on or in the box.
But a circuit breaker offers protection if things go wrong
and is highly preferable.
I have used salvaged dual and triple 100 amps house main
breakers as switches. (And
they have never blown even when things went wrong in the controller.) A
breaker rated for 240 VAC should be able to handle up to about 40 VDC.
They are, however, physically large and really require a taller chassis
box than shown.
The best breaker-switches I've found are Blue Sea
Systems panel mount breakers, rated for 48 VDC and made for marine use.
I got the 150 amps model, BSS7004. (BSS7048 has a nicer toggle handle
but costs more.) 150 amps is probably a bit larger than needed, but you
don't want it to trip when you floor the car! To mount this
requires cutting a large rectangular hole in the box. They sell a bezel
to cover inaccurate cutting. I used a file.
For vehicle use, I think at least an accessable manual
power switch is
indispensable so the car can drive on gas if there's an electric motor
or controller problem, without powering up the electric drive circuit.
A circuit breaker/switch seems to me to be much the best solution.
Mounting an ordinary "house" circuit breaker: two long bolts and a
piece of sheet metal for a clamp, plus a sized hole that fixes it in
position, are the key.
I used some #8 and even #6 jumper wires between components
chassis. I think I would now just use #10 wires unless they seem to
cause problems. They're short, so loss will be slight, and they're
considerably easier to work with. Very flexible wire is an asset,
especially to avoid stress to the wires to the motor controller, which
are attached to mechanically vulnerable components. Wire with many fine
strands is the most flexible.
Power Relay: "Solenoid" or "Contactor"
An inexpensive "solenoid" (the misleading name for 12 volt
coil contactor relays) for switching the power via the car key is
Tekonsha P/N 53536, available at RV stores. It's a little under spec on
nominal current rating (70 amps), but the motor (we trust) won't be
when it's switched on or off.
Cole-Hersee make "solenoids" with higher ratings, and I
recently found these, at a marine store. They seem rather costly.
Be sure to get one rated "continuous duty". The coil of
only made to be on for a moment (eg for a car starter motor) is likely
to burn out.
From the power disconnect breaker/switch (recommended) and
then the power "solenoid" relay (if
used), the power
line proceeds to the bus bar of the power mosfets. From here, each
phase goes through fuses to the power mosfet transistors, and their
associated filter capacitors. In the case of the
Electric HubcapTM, four common 30 amp AGO (= "AGC")
automotive fuses: 60
amps per transistor, 120 amps per phase. There is also a thin wire from
the bus bar to the circuit board to power the control logic.
Here the main battery power bus ends.
I confess to having bypassed the solenoid for testing so
far, as the
"ACC" circuit in my car doesn't seem to work, and the car won't be a
hybrid until the mechanical torque converter is working properly.
I originally used marette connectors
("wire nuts") to
tie together the heavy
wires between the motor controller, the motor drive cable, and the
spike filter components. It was a lot of work each time trying to fit
the three heavy wires into each marette.
I couldn't find suitable terminal blocks. I finally made
cube" connectors from a .5" x .75" copper bar. The holes for the wires
are first drilled right through the bar's 3/4" side. (IIRC, I used a
3/16" drill for #8 wires.) Then holes were drilled and tapped for #8-24
machine screws into the wire holes. Another #8-24 hole goes right
through the center to bolt down the cube. (Although only three wires
connect, I drilled four screw holes anyway except on the first block.)
After drilling, the piece was cut off the end of the bar, 3/4" long.
Finally, the cubes were
bolted onto a piece of dogwood, shaped and drilled as shown, via
another threaded hole at the center. (High temperature plastic would be
better - or maybe a sheet of
mylar between the copper and the wood.) The holes in the wood under the
recessed so the hold-in screws don't short to the wiring box. The
triangle pattern isn't for the benefit of the wires: it simply makes
for a firmer mounting to the box when it's screwed down.
In the first controllers, the wiring terminal blocks were in the
wiring box. They are better placed on the motor controller as shown
The base of the block, however, is angled so screwdriver handles don't
hit the other side of the box, avoiding considerable aggravation.
An alternative "brass pipe" connector block.
I also had an idea for an easier to make a unit using one
pieces of "1/8 inch" threaded brass pipe. (Actually, the inner diameter
is big enough for a #6 wire or two #8 wires.) Having thought of it, I
decided to try it and made one connector and a mounting block from a
piece of lilac wood.
I found the pipe tended to strip when the screws were
it seemed to work okay when I used a smaller than usual drill size to
ensure maximum metal in the threads. (It was hard threading the holes,
but I didn't break the threading tap.) The insides of the pipes are
bound to be corroded, whereas the copper cube holes, being freshly cut,
are clean. Cleaning inside the pipes - which I would want to do to
ensure good connections - might be more work than drilling the holes in
the copper cube.
Personally, I think the copper cubes is much the superior
system, though the pipe system is very compact and the piece of wood is
easier to make. There's lots of thread length in the cubes so the
screws won't strip with repeated insertions and removals, and being
screwed down, they can't rattle with car vibration.
I later found some commercial "bus connectors" in marine
supply stores, but they aren't as good or as compact as the cubes I
made. They generally tend to be long strips of screwdowns.
The varistors, which are pretty small, may be simply
screwed into the copper terminal blocks with the wires.
For those not familiar with metal oxide varistors ("MOV"s,
"varistors"), these interesting devices conduct exponentially more
current as the voltage rises, their resistance varying inversely with
the voltage. That helps to "short out" damaging higher voltage spikes.
The varistors I'm currently trying are "P36Z80". I tried the next
voltage rating down, "P33Z70", but a couple of them burned out during
regular motor tests. I want to use the lowest rating that lasts, to
help best protect the mosfets.
The reader should be warned that they have been known to
Like the other electronic components, they should be mounted only
inside the metal wiring box.
Seeing the sparks that result from connecting and
batteries directly to the motor coils gives one a lot of respect for
the power of the transient energies of switching the coils on and off,
of the capacity of the filters and of the electronic components to
withstand such energies repeatedly and reliably, and why power mosfets
keep going up in sparks and flame until everything is relatively
Power Wiring General Connections.
Note: DO NOT USE the 7uF "motor run" capacitors in the drawing.
It works better
without them and the spikes coming back from the motor coils seem about
the same. (And the chassis has more room without them!)
Notes on the diagram:
1. The diagram of the motor shows the 3 sets of 3 coils in parallel.
Although it shows the phases together, the parallelled coils are the
ones physically 120 degrees apart from each other.
2. Doubled varistors V36ZA80 are shown. They are currently only single
and nothing has blown up - yet. It also remains to be seen whether they
will withstand long use or whether the next voltage up will need to be
3. I've bought an inexpensive "solenoid" relay for the power via the
car key as shown, Tekonsha, P/N 53536, but I haven't
got it hooked up yet. [May 18th 2009.] It's a little under spec on
current rating (70 amps), but the motor (we trust) won't be running
when it's switched on or off.
4. Battery switches are available from marine supply stores.
I much prefer a switch that's also a circuit breaker as a disconnect in
case of any short circuit.
5. Ditch the 7uF capacitors - no value at all.