BLDC inverter output measurement

HI all,

While I was testing BLDC motor driver controller, while measuring phase to phase voltage, from the output of the motor driver IC, which is the inverter output, we were getting phase to phase voltage amplitude as 310V. Input given is 310V DC. But while checking with multimeter, we are getting 42.41V for same phase to phase voltage. Why is that? The motor controller is working. Please help with suitable reference document and formula.