# Is it time for a motor upgrade? (Current Sepex vs PM vs whatever else)



## mechman600 (Oct 16, 2010)

I am currently running a Prestolite sepex motor (MVX-4300) - about 7"X 18" long. I am feeding the armature with an Alltrax AXE7245, so 450A peak. The field gets fed by a Kelly KDS72100 that I have set to 50A max. See my signature links for full details. 

Anyway, after a drive of say 6 miles (including a 1 mile uphill climb), the motor is smoking hot - 200F+ at the commutator and 150F+ on the body. It makes me wonder how long this thing will last, though is has gone 1200 miles so far without issues. It also makes me wonder if it is time for an upgrade.

Shopping around for 8-9" series wound motors reveals that one could easily spend $1500+. But then I look at PM motors like this one: http://www.electricmotorsport.com/store/ems_ev_parts_motors_me1003.php

Pretty good specs - better than my current setup, I would guess, though I have no clue what my motor is rated for for comparison. Is there any reason that this EMC-RT200 wouldn't survive in my 3000 lb car? They claim high efficiency with these motors, so would it therefore get less smoking hot than my current motor?


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## major (Apr 4, 2008)

mechman600 said:


> But then I look at PM motors like this one: http://www.electricmotorsport.com/store/ems_ev_parts_motors_me1003.php
> ....Is there any reason that this EMC-RT200 wouldn't survive in my 3000 lb car?


You'll kill that PM motor in short order in an EVcar. Those work on carts and scooters.


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## major (Apr 4, 2008)

mechman600 said:


> ......
> Anyway, after a drive of say 6 miles (including a 1 mile uphill climb), the motor is smoking hot - 200F+ at the commutator and 150F+ on the body.....


Mech,

200ºF on the comm and 150ºF on the body (outside of the frame) isn't too hot. Limits would be like 350ºF on the comm and I don't worry about 212ºF on the outside of the frame. You say "smoking hot"  Is there smoke? 

If that motor is pulling well for you, I think you should see if you can identify if and where you have a heat problem. Perhaps you're hitting the field too hard and could get the same performance with less field current and therefore less heat. Or perhaps you need to use forced air through the motor.

A 7 inch motor is a bit on the small side for a ton and a half car especially up hill. It also depends on the gear selection and vehicle speed. No doubt an 8 or 9 incher would be stronger and run cooler, but don't go backwards with a wimpy PM 

major


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## mechman600 (Oct 16, 2010)

major, thanks again for your advice. You have made me feel better about my current (pun!) setup.

There is no smoke - I was just emphasizing "hot", but going by what you are saying, it's really not getting that hot at all. I carry a IR temp gun in the glove box to check it after longer than normal runs.

Since my commute is only 4 miles long, I am not usually concerned. However, on the way home there is a mile long hill to climb with a 4 way stop about 1/4 of the way up, and it is a real pull from there when we are talking about a peak of maybe 30 HP in a car full of lead. 50A of field puts the power peak at 25 mph in second gear (3000 rpm) and it will max out on the hill at 36 mph (4500 rpm), where I hold it all the way up to the top. When I get home, it's maybe 120F on the body and 175F on the comm.

Lowering field current would move these speeds up by a few mph but it would sacrifice acceleration from the 4-way stop sign on the hill, though I haven't really messed around with it much. Maybe I should.....


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## major (Apr 4, 2008)

Sounds like it is good the way it is


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## mechman600 (Oct 16, 2010)

OK, so the insurance runs out in August and then I am going to tackle a massive TO DO list on the Electric Booger. One of these things is forced cooling. I am thinking an eBay 90 CFM marine bilge blower (12V, 3A) should do it, considering the one meant for a Warp 9 on evsource.com (http://www.evsource.com/tls_blowers.php) is 105 CFM. The eBay ones are $25 + shipping for a pair (one for the parts bin?) on ebay: http://www.ebay.com/itm/32115275287...l?_from=R40&_sacat=0&_nkw=321152752872&_rdc=1

But how I should turn it on? My two options are:
1) epoxy a 165F (or so) thermal switch to a brush that turns the cooling fan on
2) use my [currently unused] idle microswitch to turn the cooling fan on whenever the throttle is depressed

What will work better?


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