# D&D ES-15 running at 120 volts?



## ZeroGasoline (Jul 30, 2008)

http://www.cloudelectric.com/product_p/mo-es-15-6.htm

This motor is listed as _"48-72VDC (can be used up to 120 Volts)". 

_I'm unclear on something - it's listed as a 48-72volt motor, but it can be run up to 120volts? If it can be run up to 120v, why is it not listed and marketed as such? What are the drawbacks of running this motor at 120v?

This is the motor that I have in my Tercel. I've been looking to bring the system voltage up to get a little more top speed. I'd like to be running at 96v and have been concerned that I need to buy a new motor. If I could in fact run this motor at 96v without causing any damage, that would save me a load of cash that I really don't have.

Mike Chamberlain is running the D&D ES-33 at 96v and this motor is listed as _"36-48 VDC (Can be used up to 96 Volts)". _He has not reported any problems with this on his site so I think I'd be ok running mine at 96v as well (with the option of going a little higher in the future).

Thanks in advance.


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## major (Apr 4, 2008)

ZeroGasoline said:


> What are the drawbacks of running this motor at 120v?


Hi Zero,

A lot of guys run their series motors above nameplate ratings. I don't know the specifics of this motor and won't tell you it is o.k. to run at 96 or 120 volts. I guess the right thing to do is check with the outfit that sold the motor to you, or even D&D.

As far as the draw backs to running a series motor at higher than design voltage, brush arcing and overspeed are the primary concerns. Brush arcing is a function of motor voltage, current and RPM. Some degree of arcing can be tolerated, and moderate sparking is expected. But, if the arcing is too great, a plasma ring develops around the comm and fries everything in its path. Not good. Even before this occurs, excessive arcing can put burn marks on the comm, overheat the contact surface of the brushes and ultimately cause excessive brush wear.

This condition of brush arcing at higher voltage, current and RPM can be mitigated by advancing the brushes. This moves the contact point of the brushes to the commutator relative to the magnetic field. This can be quite effective and is common with series DC motors used in EVs. The particular motor you have may or may not already have advanced brushes. Most reversible series wound motors with low voltage nameplates will be set on neutral (no advance) because the direction of rotation changes often (forward/reverse). Most EVs use the transmission for reverse, so the motor always rotates the same direction and can be advanced.

As the voltage increases for the series wound motor, the RPM increase proportionally for a given load, or current. The armature will have a limiting RPM dictated by the mechanical structure. So, when increasing the voltage in the series motor drive system, one has to pay attention to the motor speed. You likely have a multiple ratio transmission, so you can adjust your shift points to make sure you don't overspeed.

The other consideration is motor cooling. You are considering raising the voltage to increase vehicle speed. This means that the motor is going to be running at increased loads (more power). It looked like the motor has an internal fan. So, higher voltage, higher RPM, more air flow at the higher loads, better cooling; yeah, but is it enough? If you do go this route, get a temperature monitoring device, or at least, keep abreast of the motor temperature.

Regards,

major


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## ZeroGasoline (Jul 30, 2008)

major said:


> The other consideration is motor cooling. You are considering raising the voltage to increase vehicle speed. This means that the motor is going to be running at increased loads (more power). It looked like the motor has an internal fan. So, higher voltage, higher RPM, more air flow at the higher loads, better cooling; yeah, but is it enough? If you do go this route, get a temperature monitoring device, or at least, keep abreast of the motor temperature.


Thanks Major,

I appreciate your comments - I was thinking along those lines about the possible dangers of "over-volting" the motor.

Cooling is an issue now with my 72volt setup, so I'm sure it will be at 96v. I'm planning on installing a cooling fan at the same time I get the new controller and batteries in there. On hot days, it gets far too warm now. I'm hoping that with the higher voltage, I'll pull a little less current (assuming driving habits are the same) and hopefully that will relieve some of the stress on the motor. Whether it does or not the new fan should do well.


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