¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. Electricboats
  2. Topics

Electric motor and Kelly controller overheating

 

Hi
I've recently finished my conversion of a 29 Roberts 4.5 ton yacht.
1200 watt panels
270 Ah batteries at 48 volt 15s3p
Batrium BMS

My usage stats are
Rpm.? ? Amp.? Knots
530.? ? ?57
500.? ? ?44.? ? ? ?3.5
475.? ? ? 38.? ? ? 3.2
450.? ? ? 31.? ? ? 3.2
400.? ? ? 25
420.? ? ? 30
410.? ? ?28.? ? 2.4
?
?
250 rpm 6 amp
400 rpm 24 amp
450 rpm 35 amp
580 rpm 63 amp
680 rpm 95 amp

We replaced a 20hp bukh diesel and left the prop and shaft as is.
Max rpm of the diesel was 2500 with a 2.5:1 reduction ratio, so max1000 rpm on the 2 bladed 400mm diameter prop. Direct drive, no gear reduction.
Good shaft alignment can be easily rotated by hand. Easy to get cavitation if you rev up too fast.

After 20 min at 500 rpm the 120 frame AC motor reaches 80 degrees Celsius and after 40 min 120 degrees Celsius. There is sufficient ventilation.

The KAC 600 amp max 72 volt Kelly controller 8080I reaches 92 degrees after 30min and reduces high rpm to around 500 rpm and keeps them there remaining at 92 degrees Celsius.

Has anybody had a similar problem and found a good solution?
I'm not interested in cooling. I want to understand why the motor overheats at 2.5kW when it is designed to run at 4kW all day.




Thank you all for your awesome inspiration over the years. Your posts have been really helpful.

Cheers Mich
 

¿ªÔÆÌåÓý

I would first use a thermal camera on the motor and controller while at temperature. A lose connection and/or a poorly crimped cable will introduce a significant amount of heat. ?If the cables are properly sized, then they should be only slightly above ambient temperature. ?


A good thermal camera can save months of blind diagnostics, also useful for finding shorts in your navigation panel. ?


On Jan 29, 2020, at 5:15 PM, Mich Pop <michpop@...> wrote:

?Hi
I've recently finished my conversion of a 29 Roberts 4.5 ton yacht.
1200 watt panels
270 Ah batteries at 48 volt 15s3p
Batrium BMS

My usage stats are
Rpm.? ? Amp.? Knots
530.? ? ?57
500.? ? ?44.? ? ? ?3.5
475.? ? ? 38.? ? ? 3.2
450.? ? ? 31.? ? ? 3.2
400.? ? ? 25
420.? ? ? 30
410.? ? ?28.? ? 2.4
?
?
250 rpm 6 amp
400 rpm 24 amp
450 rpm 35 amp
580 rpm 63 amp
680 rpm 95 amp

We replaced a 20hp bukh diesel and left the prop and shaft as is.
Max rpm of the diesel was 2500 with a 2.5:1 reduction ratio, so max1000 rpm on the 2 bladed 400mm diameter prop. Direct drive, no gear reduction.
Good shaft alignment can be easily rotated by hand. Easy to get cavitation if you rev up too fast.

After 20 min at 500 rpm the 120 frame AC motor reaches 80 degrees Celsius and after 40 min 120 degrees Celsius. There is sufficient ventilation.

The KAC 600 amp max 72 volt Kelly controller 8080I reaches 92 degrees after 30min and reduces high rpm to around 500 rpm and keeps them there remaining at 92 degrees Celsius.

Has anybody had a similar problem and found a good solution?
I'm not interested in cooling. I want to understand why the motor overheats at 2.5kW when it is designed to run at 4kW all day.




Thank you all for your awesome inspiration over the years. Your posts have been really helpful.

Cheers Mich
<20191026_151353_HDR.jpg>
 
Edited

Hi,
I'm using a direct-drive BLDC motor and was a trouble with motor and Kelly controller overheating in the past. Problem was in high RPM motor that never can reach its optimal RPM with high torque load from big prop without reduction. Problem with overheating for both motor and controller was solver by replacing electric motor to low-RPM?one, with much better torque value at low RPM. My first motor was designed to 4000 RPM, but worked at 800 RPMmax because of it's lack of torque. Second motor have max RPM 1000 and at all useful RPM range it work a max temperature 80 celsus even after 10 hours of hard work. Controller temperature max is 60 celsus.
Considering your speed 3.5 knots @ 2.5 kW and your boat displacement I can suggest your drive work at low efficiency because of motor optimal RPM did not match your real RPM.
You have two ways to solve it: change electric motor to low RPM with higher torque or add a reduction.?
P.S. change prop to smaller one? Not a very optimal way, but it will help.

At 2.5 kW and good drive efficiency?you must reach 4.5 knots of speed.
Good luck.
Bob Jennings
 

I'm no expert but seems to me too much torque from the prop running this motor direct with no gear reduction. 80 degree Celsius is 176 degrees Fahrenheit. You could cook dinner off the motor, probably boil water when it hits 120 degrees Celsius. You may have to use a gear reduction. Just?a thought.


On Wed, Jan 29, 2020, 5:13 PM Mich Pop <michpop@...> wrote:
Hi
I've recently finished my conversion of a 29 Roberts 4.5 ton yacht.
1200 watt panels
270 Ah batteries at 48 volt 15s3p
Batrium BMS

My usage stats are
Rpm.? ? Amp.? Knots
530.? ? ?57
500.? ? ?44.? ? ? ?3.5
475.? ? ? 38.? ? ? 3.2
450.? ? ? 31.? ? ? 3.2
400.? ? ? 25
420.? ? ? 30
410.? ? ?28.? ? 2.4
?
?
250 rpm 6 amp
400 rpm 24 amp
450 rpm 35 amp
580 rpm 63 amp
680 rpm 95 amp

We replaced a 20hp bukh diesel and left the prop and shaft as is.
Max rpm of the diesel was 2500 with a 2.5:1 reduction ratio, so max1000 rpm on the 2 bladed 400mm diameter prop. Direct drive, no gear reduction.
Good shaft alignment can be easily rotated by hand. Easy to get cavitation if you rev up too fast.

After 20 min at 500 rpm the 120 frame AC motor reaches 80 degrees Celsius and after 40 min 120 degrees Celsius. There is sufficient ventilation.

The KAC 600 amp max 72 volt Kelly controller 8080I reaches 92 degrees after 30min and reduces high rpm to around 500 rpm and keeps them there remaining at 92 degrees Celsius.

Has anybody had a similar problem and found a good solution?
I'm not interested in cooling. I want to understand why the motor overheats at 2.5kW when it is designed to run at 4kW all day.




Thank you all for your awesome inspiration over the years. Your posts have been really helpful.

Cheers Mich
Kai
 

¿ªÔÆÌåÓý

What is the (temperature) rating of the motor windings?? A class F motor (winding) is rated at 155C.?

"overheating" is a relative term - a motor can be operating perfectly fine but the casing is also at the same time not touch safe.

Can you link the motor specs?


On 30/01/2020 10:24 PM, Bob Jennings wrote:

I'm no expert but seems to me too much torque from the prop running this motor direct with no gear reduction. 80 degree Celsius is 176 degrees Fahrenheit. You could cook dinner off the motor, probably boil water when it hits 120 degrees Celsius. You may have to use a gear reduction. Just?a thought.

On Wed, Jan 29, 2020, 5:13 PM Mich Pop <michpop@...> wrote:
Hi
I've recently finished my conversion of a 29 Roberts 4.5 ton yacht.
1200 watt panels
270 Ah batteries at 48 volt 15s3p
Batrium BMS

My usage stats are
Rpm.? ? Amp.? Knots
530.? ? ?57
500.? ? ?44.? ? ? ?3.5
475.? ? ? 38.? ? ? 3.2
450.? ? ? 31.? ? ? 3.2
400.? ? ? 25
420.? ? ? 30
410.? ? ?28.? ? 2.4
?
?
250 rpm 6 amp
400 rpm 24 amp
450 rpm 35 amp
580 rpm 63 amp
680 rpm 95 amp

We replaced a 20hp bukh diesel and left the prop and shaft as is.
Max rpm of the diesel was 2500 with a 2.5:1 reduction ratio, so max1000 rpm on the 2 bladed 400mm diameter prop. Direct drive, no gear reduction.
Good shaft alignment can be easily rotated by hand. Easy to get cavitation if you rev up too fast.

After 20 min at 500 rpm the 120 frame AC motor reaches 80 degrees Celsius and after 40 min 120 degrees Celsius. There is sufficient ventilation.

The KAC 600 amp max 72 volt Kelly controller 8080I reaches 92 degrees after 30min and reduces high rpm to around 500 rpm and keeps them there remaining at 92 degrees Celsius.

Has anybody had a similar problem and found a good solution?
I'm not interested in cooling. I want to understand why the motor overheats at 2.5kW when it is designed to run at 4kW all day.




Thank you all for your awesome inspiration over the years. Your posts have been really helpful.

Cheers Mich
 

Use heat sensor gun . It points out your heat problems immediately. ?Detects hidden corrosion on any contact. A must for electric boat drive ?

?Terminalift LLC
9444 Mission Park Place
Santee, CA 92071
Ph: (619) 562-0355
F: (619) 562-2060



On Thursday, January 30, 2020, 3:27:12 AM PST, Bob Jennings <heatnh@...> wrote:


I'm no expert but seems to me too much torque from the prop running this motor direct with no gear reduction. 80 degree Celsius is 176 degrees Fahrenheit. You could cook dinner off the motor, probably boil water when it hits 120 degrees Celsius. You may have to use a gear reduction. Just?a thought.


On Wed, Jan 29, 2020, 5:13 PM Mich Pop <michpop@...> wrote:
Hi
I've recently finished my conversion of a 29 Roberts 4.5 ton yacht.
1200 watt panels
270 Ah batteries at 48 volt 15s3p
Batrium BMS

My usage stats are
Rpm.? ? Amp.? Knots
530.? ? ?57
500.? ? ?44.? ? ? ?3.5
475.? ? ? 38.? ? ? 3.2
450.? ? ? 31.? ? ? 3.2
400.? ? ? 25
420.? ? ? 30
410.? ? ?28.? ? 2.4
?
?
250 rpm 6 amp
400 rpm 24 amp
450 rpm 35 amp
580 rpm 63 amp
680 rpm 95 amp

We replaced a 20hp bukh diesel and left the prop and shaft as is.
Max rpm of the diesel was 2500 with a 2.5:1 reduction ratio, so max1000 rpm on the 2 bladed 400mm diameter prop. Direct drive, no gear reduction.
Good shaft alignment can be easily rotated by hand. Easy to get cavitation if you rev up too fast.

After 20 min at 500 rpm the 120 frame AC motor reaches 80 degrees Celsius and after 40 min 120 degrees Celsius. There is sufficient ventilation.

The KAC 600 amp max 72 volt Kelly controller 8080I reaches 92 degrees after 30min and reduces high rpm to around 500 rpm and keeps them there remaining at 92 degrees Celsius.

Has anybody had a similar problem and found a good solution?
I'm not interested in cooling. I want to understand why the motor overheats at 2.5kW when it is designed to run at 4kW all day.




Thank you all for your awesome inspiration over the years. Your posts have been really helpful.

Cheers Mich
 

Do you have a thrust bearing?
Seems like something is wrong, based on your power useage.

On Thu, Jan 30, 2020, 7:42 AM Kai <kai@...> wrote:
What is the (temperature) rating of the motor windings?? A class F motor (winding) is rated at 155C.?

"overheating" is a relative term - a motor can be operating perfectly fine but the casing is also at the same time not touch safe.

Can you link the motor specs?


On 30/01/2020 10:24 PM, Bob Jennings wrote:
I'm no expert but seems to me too much torque from the prop running this motor direct with no gear reduction. 80 degree Celsius is 176 degrees Fahrenheit. You could cook dinner off the motor, probably boil water when it hits 120 degrees Celsius. You may have to use a gear reduction. Just?a thought.

On Wed, Jan 29, 2020, 5:13 PM Mich Pop <michpop@...> wrote:
Hi
I've recently finished my conversion of a 29 Roberts 4.5 ton yacht.
1200 watt panels
270 Ah batteries at 48 volt 15s3p
Batrium BMS

My usage stats are
Rpm.? ? Amp.? Knots
530.? ? ?57
500.? ? ?44.? ? ? ?3.5
475.? ? ? 38.? ? ? 3.2
450.? ? ? 31.? ? ? 3.2
400.? ? ? 25
420.? ? ? 30
410.? ? ?28.? ? 2.4
?
?
250 rpm 6 amp
400 rpm 24 amp
450 rpm 35 amp
580 rpm 63 amp
680 rpm 95 amp

We replaced a 20hp bukh diesel and left the prop and shaft as is.
Max rpm of the diesel was 2500 with a 2.5:1 reduction ratio, so max1000 rpm on the 2 bladed 400mm diameter prop. Direct drive, no gear reduction.
Good shaft alignment can be easily rotated by hand. Easy to get cavitation if you rev up too fast.

After 20 min at 500 rpm the 120 frame AC motor reaches 80 degrees Celsius and after 40 min 120 degrees Celsius. There is sufficient ventilation.

The KAC 600 amp max 72 volt Kelly controller 8080I reaches 92 degrees after 30min and reduces high rpm to around 500 rpm and keeps them there remaining at 92 degrees Celsius.

Has anybody had a similar problem and found a good solution?
I'm not interested in cooling. I want to understand why the motor overheats at 2.5kW when it is designed to run at 4kW all day.




Thank you all for your awesome inspiration over the years. Your posts have been really helpful.

Cheers Mich

1 - 7 of 7