Firstly, I apologies for having to ask such a basic question.

I'm looking to buy a controller for a permanent magnet motor. The specs of the motor are: 200VDC, 1.5HP, 5700RPM, 7.6A, form factor: 1.0

I am trying to decide between two controllers that I have seen on ebay:

500w, 4A

800W, 8A

The cheaper one has the following specs: DC 0-220V (output), 4A, 500W

The more expensive has these specs: DC 0-220V, 8A, 800W

My question is: what will happen if I tried to run the motor with the first controller?

The motor draws 7.6A but the controller is rated at 4A. Will it run at half torque? Will the motor cause damage to the controller/vice versa?

(...or am I better off getting the 800W controller?)

  • 1
    \$\begingroup\$ It'll work like crap, for varying definitions of "crap". \$\endgroup\$ May 14, 2014 at 0:12

1 Answer 1


The controller rated at 4 amps won't be suitable for your motor. You shouldn't attempt to overload this smaller controller, unless you have a lot of in depth knowledge of motors and controllers.

The direct answer is : the cheaper (4 amp) controller will fail with your load if you try to use the motor at full load.

  • \$\begingroup\$ So would the 8A controller be suitable? \$\endgroup\$ May 14, 2014 at 19:57
  • \$\begingroup\$ The 8A does allow for your 7.6A requirement. It should work. However, if your motor load is going to be maximum at all times, it would be like running your automobile at full speed. Personally I don't like to operate power products at 95% of their ability. \$\endgroup\$
    – Marla
    May 14, 2014 at 20:04

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