AB drive overheating

  • Thread starter Pierre Desrochers
  • Start date

Thread Starter

Pierre Desrochers

Hi- We have a problem with a 1336S drive from AB. We get a failure
every time the ambiant temperature reaches 35C. It's installed in a
panel (80x48x14). The heatsink are external and clean. We have
installed an air conditionning unit with 4000BTU capacity. The drive
supply's 250 Amps at 575 Volts. It's controled via HMI and PID loop.
Can you give us a hint on what to do or what the causes could be.


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Robert R. Stephens Pennzoil Products


I've got GE AF$300 drive, 250 HP that also requires cooling to keep it
operational. I can tell you we started with a small AC and ended up adding a
larger one. We found 12,000 Btu total required to cool the drive. The
cabinet size was approximately 72HX36WX24D. No problems since then though.

Good Luck.

I thought overtemperature would be the least of potential problems in Quebec
this time
of year !

The A-B 1336 PLUS drive has a thermistor embedded in the heatsink. This will
give you an over-temperature drive fault (The message reads "F08 Overtemp
Fault") if it
senses the heatsink temperature being too high.

The sensor itself is monitored for open-circuit (that will generate an F55 Temp
Sense Open fault)
and the monitored temperature is available as Parameter 70.

The drive's temperature trip point is 90 C (195 F). The ambient operating
temperature for which
the drive is rated is 40 C.

Check to be sure that the thermistor is reading correctly the heatsink
temperature (you can easily trend
Parameter 70 if you have RIO, CNet, or DNet comms to the drive).

I don't know enough about HVAC capacity to advise on how much chilling is
you might want to increase airflow over the heatsink itself, since
you said it's external to the air-conditioned cabinet.

Nick Haddock


I've not had this problem with an AB drive but have found a faulty
temperature sensor on an SSD drive
giving the same symtoms. The sensor was a PTC with a bad connection (Bad
connection gives high
resistance, high resistance = high temperaure on a PTC). The sensor was
fitted to the heat sink of the
Although your heatsink is external and clean there could be a hot spot
caused by a bad contact of the thyristor
to the heatsink, you could verify this if you can get access to the
thyristors easily.

I hope this is of help and hope I am not "Teaching Granny to suck eggs".

Regards Nick Haddock
I am not familiar with this specific drive. In general, assuming the failure
is a drive overheating fault and not an external fault, telling drive to
shut-down e.g. motor thermal contact, you need to first determine the total
power dissipation in the cabinet from ALL heat generating devices. Drive
manual should give Pdiss at full-load, or use efficiency data. Calculate
based on actual load. You mentioned "external" heatsink. If the drive
installation is with heatsink through cabinet, AB should specify effective %
heat generated into cabinet by this installation method. Cabinet suppliers
have application sizing formulas/programs in their catalogs or by software,
web site etc. Basically, you need to verify the cabinet size/AC cooling is
sufficient to remove total effective Pdiss at 35C.


Mark Sevelis

I work in AB Standard Drives Technical Support...

F08 Overtemp is caused by heatsink temp >90` C.

1) What is the heatsink temp parameter? parm #70.
2) Is drive is a dusty environment?
3) Check if heatsink fins are blocked by any debris
4) Are the internal and external fans blocked by any debris?
5) What is the catalog number of this drive?

Advise. Mark Sevelis

note: I'm surprised there are so few drives questions;
everything seems to be only PLC's!

Alex Ruderman

I would like to take this opportunity to have a general talk about motor loss / heat dissipation. Additional PWM induced machine iron loss for classic 3-phase 6-switch inverter topology is reportedly of the order of that induced by main magnetic flux (I can provide a reference). I believe that machine PWM induced iron loss might be aggressively - 3-4 times - reduced. This way, PWM iron loss reduction is probably a source for overall heat dissipation decrease (especially in energy conservation applications) that is not yet well recognized by power electronics / motor control community. I developed simple machine PWM iron loss PWM frequency and speed dependency theory that is in agreement with published experimental data (too long to be published overhere). Based on this theory, I identified some novel power stage topologies (plus matching PWM switching patterns) capable of 3-4 times on average machine PWM iron loss reduction. Especially attractive due to their simplicity are switched reluctance motor (generator) and 3-phase unity power factor PWM rectifier topologies. For example, 3-phase unity power factor PWM rectifier topology comprises 3 (minimum)semiconductor switches rated at about 50% power of those of classic inverter topology. Along with efficiency increase which is definitely a premium for energy conservation applications, PWM iron loss reduction is good for industrial applications - less machine power derating, easier cooling, more overload, lower lamination cost, longer bearings life etc. -Alex [email protected]