Rated Voltage of a DC Motor VS PWM Control

It would be something that I would consider to be fully possible, provided you make sure that you never to "over drive" the motor voltage.......as this would probably shorten the motor's life quite radically......

Just make sure that the average voltage the motor sees is not more than 110 volts.

You might start out with say 90-100 volts and see how the motor handles that first before raising to 110 volts, just as a safety step.....

Keep us fully informed please.

By the way, I have never done this personally in the manner you describe, but I cannot see any errors of thinking.....lets see what others feel!!

Having worked at a lab many years ago where DC motor control was being developed, I believe that if you use a diode across the motor so that the instantaneous voltage isn't extreme, you should be able to do what you want with little problem.

The motor provides an inductive load and the diode allows the current in the motor to decay without the large voltage spike which could potentially arc over the windings.

We used a bank of car batteries totaling about 130 volts. Impressive especially when an electrolytic capacitor gives up and spews its insides all over, or when a technician gets angry and throws a large wrench on top of the battery bank because he forgot the safety knife switch for positive disconnect.

I would be surprised to find that the insulation of your motor windings had a break down voltage limit that was close (150V) to your designed operating voltage (110V). By adding a fly-back (reverse biased) diode across the motor winding, as Bill suggested, you will keep the motor winding voltage to a not much more than the 150V you are applying. Likely the PWM driver power MOSFETs already have reverse bias body diodes. I would not rely on these though to handle the current. Select a diode rated for the full current that the motor takes and to handle at least the expected reverse voltage applied. Now if you wish to be clever, you might consider putting a power resistor in series with this reverse biased diode. This will add dynamic braking to your motor function. This will be lost energy in your system and as such may not be desired though. A more in depth analysis of your drive circuitry may permit you to divert the fly-back current to be stored into a capacitor to permit a more efficient use of the energy stored in the motor and the mass that it is moving.

The PWM control provides, pulses the duration of which varies, thus the output that integrates on the coils of motor stabilizes at certain level depending on the duration of the pulses. Shorter pulse provides lower voltage! Longer pulse provides higher voltage. In this way motor speed varies.

This, what you have is a typical, mismatch of battery and motor. You can replace motor for smaller or battery for larger.

Good luck! Tell me what car would use your solution I would make sure not buying it!

Hybrid technology is another technological blunder that relates to wrong research trend.

Actually for Hybrids it is better to use three phase motor supplied from frequency inverter, so frequency variation causes speed variations. The DC motors are very inefficient and not very reliable.

If you haven't already, you might want to consider enhancing the method used to dissipate motor heat. This can reduce stress on motor insulation. If this is a brush type motor, try keeping the brush lead length at a maximum permitted. This helps to dissipate heat as well.

I don't know how many amps your motor takes, so what I am now going to say may be impractical, but adding a large capacitor across the motor will smooth out the pulses. Allowing the voltage charge on the cap to be maintained at the 110 volts the motor needs....

This should stop stressing the motor with peaks of more than 110 volts......(though I personally do not think that they would have hurt anything anyway!, the average voltage is what counts).....

Great!

Thanks a lot for your help. We will consider the option of a diode and condensator. Our motor max peak current is 400A.

We are waiting for feedback from the supplier to verify if the wires of the motor can handle more than 110 peak. Lets see what it gives.

Cya!

Renaud